Tue·Dec 15, 2020Tuesday·December 15, 2020

1. 01*

   Reviving the interference: framework and proof-of-principle for the anomalous gluon self-interaction in the SMEFT

   Celine Degrande🇧🇪 · Matteo Maltoni🇧🇪

   Interferences are not positive-definite and can change sign over the phase space. If the contributions of the regions where they are positive and negative nearly cancel each other, their effects can be hard to measure. In this paper, we propose a method to quantify the ability of an observable to separate these opposite contributions and therefore to revive the interference effects at experiments. We apply this strategy to the anomalous gluon operator in the SMEFT, for which the linear-term suppression is well known. We show that we can get, for the first time, constraints on its coefficient from the interference only that are similar to those from the square of the new-physics amplitude.

   hep-phPRD(2021)·9 citations
2. 02*

   Electroweak precision pseudo-observables at the $e^{+}{e}^{-}$ Z-resonance peak

   Ievgen Dubovyk🇵🇱 · Ayres Freitas🇺🇸 · Janusz Gluza🇵🇱 · Krzysztof Grzanka🇵🇱 · Tord Riemann🇵🇱 · Johann Usovitsch🇩🇪

   Phenomenologically relevant electroweak precision pseudo-observables related to Z-boson physics are discussed in the context of the strong experimental demands of future $e^{+}{e}^{-}$ colliders. The recent completion of two-loop Z-boson results is summarized and a prospect for the 3-loop Standard Model calculation of the Z-boson decay pseudo-observable is given.

   hep-phPoS(2021)·0 citations
3. 03*

   Baryonic Higgs and Dark Matter

   Pavel Fileviez Perez🇺🇸 · Clara Murgui🇺🇸 · Alexis D. Plascencia🇺🇸

   We discuss the correlation between dark matter and Higgs decays in gauge theories where the dark matter is predicted from anomaly cancellation. In these theories, the Higgs responsible for the breaking of the gauge symmetry generates the mass for the dark matter candidate. We investigate the Higgs decays in the minimal gauge theory for Baryon number. After imposing the dark matter density and direct detection constraints, we find that the new Higgs can have a large branching ratio into two photons or into dark matter. Furthermore, we discuss the production channels and the unique signatures at the Large Hadron Collider.

   hep-phhep-exJHEP(2021)·5 citations
4. 04*

   Low energy implications of cosmological data in $U(1{)}_X$ Higgs inflation

   Shinsuke Kawai🇰🇷 · Nobuchika Okada🇺🇸 · Satomi Okada🇺🇸

   A scalar field having the Coleman-Weinberg type effective potential arises in various contexts of particle physics and serves as a useful framework for discussing cosmic inflation. According to recent studies based on the Markov chain Monte Carlo analysis, the coefficients of such an effective potential are severely constrained by the cosmological data. We investigate the impact of this observation on the physics beyond the Standard Model, focusing on an inflationary model based on the $U(1{)}_X$-extended Standard Model as a well-motivated example. We examine the parameter region that is not excluded by the Large Hadron Collider (LHC) Run-2 at 139 fb${}^{-1}$ integrated luminosity, and show that the model parameters can be further constrained by the High-Luminosity LHC experiments in the near future. We also comment on the possible reheating mechanism and the dark matter candidates of this scenario.

   hep-phastro-ph.COhep-exPRD(2021)·5 citations
5. 05*

   Power corrections to event shapes using eikonal dressed gluon exponentiation

   Neelima Agarwal · Ayan Mukhopadhyay🇮🇳 · Sourav Pal🇮🇳 · Anurag Tripathi🇮🇳

   Event shapes are classical tools for the determination of the strong coupling and for the study of hadronization effects in electron-positron annihilation. In the context of analytical studies, hadronization corrections take the form of power-suppressed contributions to the cross-section, which can be extracted from the perturbative ambiguity of Borel-resummed distributions. We propose a simplified version of the well-established method of Dressed Gluon Exponentiation (DGE), which we call Eikonal DGE (EDGE), which determines all dominant power corrections to event shapes by means of strikingly elementary calculations. We believe our method can be generalized to hadronic event shapes and jet shapes of relevance for LHC physics.

   hep-phJHEP(2021)·17 citations
6. 06*

   Matching in $pp\to t\bar{t}W/Z/h+$ jet SMEFT studies

   Reza Goldouzian (1)🇺🇸 · Jeong Han Kim (1 and 2)🇰🇷 · Kevin Lannon (1)🇺🇸 · Adam Martin (1)🇺🇸 · Kelci Mohrman (1)🇺🇸 · Andrew Wightman (1) ((1) University of Notre Dame, (2) Chungbuk National University)🇺🇸

   In this paper, we explore the impact of extra radiation on predictions of $pp\to t\bar{t}X,X=h/W^{\pm }/Z$ processes within the dimension-6 SMEFT framework. While full next-to-leading order calculations are of course preferred, they are not always practical, and so it is useful to be able to capture the impacts of extra radiation using leading-order matrix elements matched to the parton shower. While a matched leading-order calculation for $t\bar{t}X$ is not expected to reproduce the next-to-leading order inclusive cross section precisely, we show that it does capture the relative impact of the EFT effects by considering the ratio of matched SMEFT inclusive cross sections to Standard Model values, ${\sigma }_{\mathrm{SMEFT}}(t\bar{t}Xj)/{\sigma }_{\mathrm{SM}}(t\bar{t}Xj)\equiv \mu$. Furthermore, we compare leading order calculations with and without extra radiation and find several cases, such as the effect of the operator $({\phi }^{†}i{\overleftrightarrow{D}}_{\mu }\phi )(\bar{t}{\gamma }^{\mu }t)$ on $t\bar{t}h$ and $t\bar{t}W$, for which the relative cross section prediction increases by more than $10\%$ -- significantly larger than the uncertainty derived by varying the input scales in the calculation, including the additional scales required for matching. Being leading order at heart, matching has the benefit that it can be applied to all operators and processes relevant to $pp\to t\bar{t}X,X=h/W^{\pm }/Z+$ jet, is computationally fast and not susceptible to negative weights. Therefore, it is a useful approach in $t\bar{t}X+$ jet studies where complete next-to-leading order results are currently unavailable or unwieldy.

   hep-phJHEP(2021)·19 citations
7. 07*

   Neutrino eigenstates and flavour, spin and spin-flavour oscillations in a constant magnetic field

   Alexey Lichkunov🇷🇺 · Artem Popov🇷🇺 · Alexander Studenikin🇷🇺

   We develop the approach to the problem of neutrino oscillations in a magnetic field introduced in \cite{Popov:2019nkr} and extend it to the case of three neutrino generations. The theoretical framework suitable for computation of the Dirac neutrino spin, flavour and spin-flavour oscillations probabilities in a magnetic field is given. It is shown that there is an entanglement between neutrino flavour and spin oscillations and in the general case it is not possible to consider these two types of neutrino oscillations separately. The closed analytic expressions for the probabilities of oscillations are obtained accounting for the normal and inverted hierarchies and the possible effect of CP violation. In particular, it is shown that the probabilities of the conversions without neutrino flavor change, i.e. ${\nu }_e^L\to {\nu }_e^L$ and ${\nu }_e^L\to {\nu }_e^R$, do not exhibit the dependence on the CP phase, while the other neutrino conversions are affected by the CP phase. In general, the neutrino oscillation probabilities exhibit quite a complicated interplay of oscillations on the magnetic ${\mu }_{\nu }B$ and vacuum frequencies. The obtained results are of interest in applications to neutrino oscillations under the influence of extreme astrophysical environments, for example peculiar to magnetars and supernovas, as well as in studying neutrino propagation in interstellar magnetic fields.

   hep-phastro-ph.HEPoS(EPS-HEP2019)429·3 citations
8. 08*

   Gravitational form factors of $N(1535)$ in QCD

   K. Azizi🇮🇷 · U. Özdem🇹🇷

   We calculate the gravitational form factors of the excited $N(1535)$ state with the quantum numbers $I(J^P)=\frac{1}{2}({\frac{1}{2}}^{-})$ via light cone QCD sum rules (LCSR). To this end, we consider the quark part of the energy-momentum tensor (EMT) current and use the general form of the nucleon's interpolating field as well as the distribution amplitudes (DAs) of $N(1535)$. As both the nucleon and $N(1535)$ couple to the same current, the $N(1535)\to N$ gravitational transition form factors are entered to the calculations as the main input parameters. First we revisit the transitional gravitational form factors of $N(1535)\to N$, then extract the values of the form factors of the $N(1535)$ excited state. We observe that the gravitational form factors of $N(1535)$ in terms of $Q^2$ are well described by the multipole fit function. As a byproduct, we also calculate the pressure and energy density at the center of $N(1535)$ and estimate its mechanical radius.

   hep-phhep-exhep-latNPA(2021)·13 citations
9. 09*

   Explaining electron and muon $g-2$ anomalies in an Aligned 2-Higgs Doublet Model with Right-Handed Neutrinos

   Luigi Delle Rose🇪🇸 · Shaaban Khalil🇪🇬 · Stefano Moretti🇬🇧

   We explain anomalies currently present in various data samples used for the measurement of the anomalous magnetic moment of electron ($a_e$) and muon ($a_{\mu }$) in terms of an Aligned 2-Higgs Doublet Model with right-handed neutrinos. The explanation is driven by one and two-loop topologies wherein a very light CP-odd neutral Higgs state ($A$) contributes significantly to $a_{\mu }$ but negligibly to $a_e$, so as to revert the sign of the new physics corrections in the former case with respect to the latter, wherein the dominant contribution is due to a charged Higgs boson ($H^{\pm }$) and heavy neutrinos with mass at the electroweak scale. For the region of parameter space of our new physics model which explains the aforementioned anomalies we also predict an almost background-free smoking-gun signature of it, consisting of $H^{\pm }A$ production followed by Higgs boson decays yielding multi-$\tau$ final states, which can be pursued at the Large Hadron Collider.

   hep-phhep-thPLB(2021)·41 citations
10. 10*

    Light-cone sum rules for radial excitation of decuplet to octet baryons electromagnetic transition form factors

    T.M.Aliev🇹🇷 · M.Savci🇹🇷 · S.Bilmis🇹🇷

    Magnetic dipole moment form factor, $G_M^{(2)}(Q^2)$, describing the radial excitation of decuplet baryons to octet baryons electromagnetic transitions as well as the ratios, $R_{SM}=-\frac{1}{4m_2^2}\sqrt{4m_2^2{Q}^2+(m_2^2-Q^2-m_1^2{)}^2}\frac{G_C^{(2)}(Q^2)}{G_M^{(2)}(Q^2)}$ and $R_{EM}=-\frac{G_E^{(2)}(Q^2)}{G_M^{(2)}(Q^2)}$ are calculated in the framework of light-cone sum rules. We also estimate the degree of the violation of U-spin symmetry. The obtained results for the multipole form factors can be useful in searching the properties of radially excited baryon states.

    hep-phMod.Phys.Lett.A(2021)·0 citations
11. 11*

    Energy-driven disorder in the mean field QCD

    Sergei N. Nedelko🇷🇺 · Vladimir E. Voronin🇷🇺

    An impact of the finite size effects on the vacuum free energy density of full QCD with $N_{\mathrm{f}}$ massless flavors in the presence of homogeneous (anti-)self-dual Abelian background gluon field is studied. The zero temperature free energy density of the four-dimensional spherical domain is computed as a function of the background field strength $B$ and domain radius $R$. Calculation is performed in the one-loop approximation improved by accounting for mixing of the quark and gluon quasi-zero modes with normal modes, with the use of the $\zeta$-function regularization. It is indicated that, under plausible assumption on the character of the mixing, the quantum correction to the free energy density has a minimum as a function of $B$ and $R$. Within the mean field approach to QCD vacuum based on domain wall network representation of the mean field, an existence of the minimum may prevent infinite growth of individual domain, thus protecting the vacuum from the long-range ordering, and, hence, serving as the origin of disorder in the statistical ensemble of domain wall networks, driven by the minimization of the overall free energy of the dominant gauge field configurations.

    hep-phPRD(2021)·6 citations
12. 12*

    Challenges for tau physics at the TeraZ

    Antonio Pich🇪🇸

    The very high statistics, low backgrounds and clean back-to-back kinematics of a TeraZ facility would provide an optimal laboratory for precision measurements of the $\tau$ properties. A few important topics in $\tau$ physics where very relevant contributions could be made are highlighted.

    hep-phEur.Phys.J.Plus(2021)·24 citations
13. 13*

    Relativistic Freeze-in with Scalar Dark Matter in a Gauged $B-L$ Model and Electroweak Symmetry Breaking

    Priyotosh Bandyopadhyay🇮🇳 · Manimala Mitra🇮🇳 · Abhishek Roy🇮🇳

    We explore relativistic freeze-in production of scalar dark matter in gauged $B-L$ model, where we focus on the production of dark matter from the decay and annihilation of Standard Model (SM) and $B-L$ Higgs bosons. We consider the Bose-Einstein (BE) and Fermi-Dirac (FD) statistics, along with the thermal mass correction of the SM Higgs boson in our analysis. We show that in addition to the SM Higgs boson, the annihilation and decay of the $B-L$ scalar can also contribute substantially to the dark matter relic density. Potential effects of electroweak symmetry breaking (EWSB) and thermal mass correction in BE framework enhance the dark matter relic substantially as it freezes-in near EWSB temperature via scalar annihilation. However, such effects are not so prominent when the dark matter freezes-in at a later epoch than EWSB, dominantly by decay of scalars. The results of this analysis are rather generic, and applicable to other similar scenarios.

    hep-phastro-ph.COJHEP(2021)·12 citations
14. 14*

    Mass corrections to the DGLAP equations

    Ahmad Jamali Hafshejani🇮🇷 · Abolfazl Mirjalili🇮🇷

    We propose a mass-dependent MOM scheme to renormalize UV divergence of unpolarized PDFs at one-loop order. This approach which is based on a once subtracted dispersion relation does not need any regulator. The overall counterterms are obtained from the imaginary part of large transverse momentum region in loop integrals. The mass-dependent characteristic of the scheme yields to mass-dependent splitting functions for the DGLAP evolution equations. While the flavor number is fixed at any renormalization scale, the decoupling theorem is automatically imposed by the mass-dependent splitting functions. The required symmetries are also automatically respected by our prescription.

    hep-phPRD(2021)·0 citations
15. 15*

    Response of a weakly magnetized hot QCD medium to inhomogeneous electric field

    Gowthama K K🇮🇳 · Manu Kurian🇮🇳 · Vinod Chandra🇮🇳

    The electric charge transport in a weakly magnetized hot QCD medium has been investigated in the presence of an external inhomogeneous electric field. The current densities (electric and Hall)induced by the inhomogeneous electric field have been estimated in the regime where space-time inhomogeneity of the field is small so that the collisional effect in the medium cannot be neglected. The collisional aspect of the medium has been captured by employing both relaxation time approximation and Bhatnagar-Gross-Krook collision kernel in the relativistic Boltzmann equation. The magnetic field, momentum anisotropy, and quark chemical potential dependences of the electric current and Hall current densities have been explored, and the impacts on the respective conductivities have been studied. The inhomogeneities of the field are seen to have sizable effects on the electromagnetic responses of the collisional medium.

    hep-phPRD(2021)·19 citations
16. 16*

    Interplay between the factorization of the Jarlskog Invariant and location of the Solar and Atmospheric Resonances for Neutrino Oscillations in Matter

    Stephen J. Parke🇺🇸

    The Jarlskog invariant which controls the size of intrinsic CP violation in neutrino oscillation appearance experiments is modified by Wolfenstein matter effects for neutrinos propagating in matter. In this paper we give the exact factorization of Jarlskog invariant in matter into the vacuum Jarlskog invariant times two, two-flavor matter resonance factors that control the matter effects for the solar and atmospheric resonances independently. We compare the location of the minima of the factorizing resonance factors with the location of the solar and atmospheric resonances, precisely defined. They are not identical but the fractional differences are both found to be less than 0.1\%. In addition, we explain why symmetry polynomials of the square of the mass of the neutrino eigenvalues in matter, such as inverse of the square of the Jarlskog invariant in matter, can be given as polynomials in the matter potential.

    hep-phhep-exPRD(2021)·4 citations
17. 17*

    Frozen-in fermionic singlet dark matter in non-standard cosmology with a decaying fluid

    Paola Arias🇨🇱 · Dimitrios Karamitros🇵🇱 · Leszek Roszkowski🇵🇱

    We perform a detailed study of dark matter production via freeze-in under the assumption that some fluid dominates the early Universe before depositing its energy to the plasma causing entropy injection. As a dark matter candidate we consider a fermionic singlet that is produced through its interactions with a scalar particle in the thermal plasma. The fluid alters the expansion rate of the Universe, as well as the scaling of the temperature, which significantly affects the evolution of both the number density and the mean momentum of the dark matter particle. We identify and discuss in detail the effects of the evolution of these quantities by considering several examples representing dark matter production at different stages of expansion and entropy injection. We find that, since the dark matter density is reduced when the entropy injection to the plasma continues after freeze-in, in order to reproduce its observational value an enhanced rate of dark matter production is required relative to standard cosmology. Furthermore, the impact of the assumed non-standard cosmological history on the dark matter mean momentum can result in either a relaxed or a tightened bound on the dark matter mass from large structure formation data.

    hep-phJCAP(2021)·13 citations
18. 18*

    Interpretation of XENON1T excess with MeV boosted dark matter

    Lian-Bao Jia🇨🇳 · Tong Li🇨🇳

    The XENON1T excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with MeV mass and high-speed. We consider a tangible model composed of two scalar MeV dark matter (DM) particles $S_A$ and $S_B$ to interpret the XENON1T keV excess via boosted $S_B$. A small mass splitting $m_{S_A}-m_{S_B}>0$ is introduced and the boosted $S_B$ can be produced by the dark annihilation process of $S_A{S}_A^{†}\to \varphi \to S_B{S}_B^{†}$ via a resonant scalar $\varphi$. The $S_B-$electron scattering is intermediated by a vector boson $X$. Although the constraints from BBN, CMB and low-energy experiments set the $X-$mediated $S_B-$electron scattering cross section to be $\lesssim 10^{-35}{\mathrm{cm}}^2$, the MeV scale DM with a resonance enhanced dark annihilation today can still provide enough boosted $S_B$ and induce the XENON1T keV excess. The relic density of $S_B$ is significantly reduced by the $s$-wave process of $S_B{S}_B^{†}\to XX$ which is allowed by the constraints from CMB and 21-cm absorption. A very small relic fraction of $S_B$ is compatible with the stringent bounds on un-boosted $S_B$-electron scattering in DM direct detection and the $S_A$-electron scattering is also allowed.

    hep-phastro-ph.COCPC(2022)·7 citations
19. 19*

    The scalar potential of the 331 model: theoretical constraints

    Antonio Costantini🇮🇹

    We discuss the main features of the scalar sector of a class of BSM models with enlarged gauge symmetry, the so called 331 Models. The theoretical constraints on the scalar potential such as unitarity, perturbativity and boundedness-from-below, are presented, together with the analytical exact digitalization of the scalar sector. The phenomenology of exotic scenarios predicted by the 331 Models can be tested in light of these theoretical constraints.

    hep-phPoS(2021)·0 citations
20. 20*

    Searching for New Physics with $B^0\to K^{\ast 0}{\mu }^{+}{\mu }^{-}$

    S. Neshatpour🇫🇷 · T. Hurth🇩🇪 · F. Mahmoudi🇫🇷

    One of the main indications for New Physics in rare $B$-decays is deduced from the tension between experimental and Standard Model predictions of the angular analysis of the $B^0\to K^{\ast 0}{\mu }^{+}{\mu }^{-}$ decay. There are however possible non-local hadronic effects which in principle can also explain these tensions. In this work, we consider a statistical approach for differentiating the source of the tension in $B^0\to K^{\ast 0}{\mu }^{+}{\mu }^{-}$ observables and we also investigate the prospects of such a comparison with future data from the LHCb experiment.

    hep-phPoS(2021)·1 citation
21. 21*

    On interference effects in top-philic decay chains

    Oliver Atkinson🇬🇧 · Christoph Englert🇬🇧 · Panagiotis Stylianou🇬🇧

    Sizeable exotic Higgs boson production through gluon fusion via top quark loops is correlated with large Higgs decay probabilities into top quark final states, if these are kinematically accessible. It is known that $gg\to S\to t\bar{t}$ is particularly susceptible to signal-background interference effects that can significantly impact discovery sensitivities. In such an instance, identifying more robust signatures to enhance the discovery sensitivity becomes necessary, shifting phenomenological focus to final states that show a reduced destructive signal-background interference. In this work, we discuss the phenomenological relevance of signal-signal and signal-background interference effects for decay chains. In particular, we identify asymmetric cascade decays in models of scalar extensions of the SM Higgs sector as new promising candidates. In parallel, characteristic interference patterns can provide a formidable tool for indirect CP spectroscopy of BSM sectors if a discovery is made in the future. This motivates associated searches at present and future colliders as robust discovery modes of new physics, in addition to serving as a sensitive tool for the reconstruction of the underlying UV electroweak potential.

    hep-phhep-exPLB(2021)·7 citations
22. 22*

    Gravity Resonance Spectroscopy and Dark Energy Symmetron Fields

    Tobias Jenke🇫🇷 · Joachim Bosina🇦🇹 · Jakob Micko🇫🇷 · Mario Pitschmann🇦🇹 · Rene Sedmik🇦🇹 · Hartmut Abele🇦🇹

    Spectroscopic methods allow to measure energy differences with unrivaled precision. In the case of gravity resonance spectroscopy, energy differences of different gravitational states are measured without recourse to the electromagnetic interaction. This provides a very pure and background free look at gravitation and topics related to the central problem of dark energy and dark matter at short distances. In this article we analyse the effect of additional dark energy scalar symmetron fields, a leading candidate for a screened dark energy field, and place limits in a large volume of parameter space.

    hep-phnucl-exEur.Phys.J.ST(2021)·30 citations
23. 23*

    Probing hidden-bottom pentaquarks in fixed-target collisions at the LHC

    Ya-Ping Xie🇨🇳 · Victor P. Goncalves🇧🇷

    In this paper we investigate the possibility of searching for the hidden-bottom pentaquark states in photon-induced interactions at the LHC. We consider the presence of the $P_b$ resonance in the $s$-channel of the $\gamma p\to {\rm Y}p$ reaction and estimate its contribution for the exclusive ${\rm Y}$ photoproduction in the fixed-target mode of the LHC. Predictions for the total cross sections, rapidity and transverse momentum distributions are derived using the STARlight Monte Carlo considering $Pb-p$, $Pb-He$ and $Pb-Ar$ fixed-target collisions at the LHC. Our results indicate that the presence of the $P_b$ resonance implies an enhancement in the rapidity distribution in the kinematical range covered by the LHCb detector. We demonstrate that the $P_b$ contribution for the ${\rm Y}$ photoproduction becomes dominant if kinematical cuts are imposed on the rapidity and transverse momentum of the final state. These results indicate that an experimental analysis of the ${\rm Y}$ photoproduction in fixed-target collisions can provide complementary and independent checks of the existence of these states, and help to understand their underlying nature.

    hep-phhep-exPLB(2021)·13 citations
24. 24*

    Competition of inhomogeneous chiral phases and two-flavor color superconductivity in the NJL model

    Phillip Lakaschus🇩🇪 · Michael Buballa🇩🇪 · Dirk H. Rischke🇩🇪

    We study the phase structure of the two-flavor Nambu--Jona-Lasinio (NJL) model in the chiral limit, extending a previous study of the competition of an inhomogeneous chiral phase and a two-flavor color-superconducting (2SC) phase [1, 2]. There, an analytic expression for the dispersion relations for quasiparticle excitations in the presence of both a particular inhomogeneous chiral condensate, the so-called chiral density wave (CDW), and a homogeneous 2SC condensate was found. In this work we show how to determine the dispersion relations for arbitrary modulations of the chiral condensate in the presence of a homogeneous 2SC condensate, if the dispersion relations in the absence of color superconductivity are known. In our calculations, we employ two different Ansätze for the inhomogeneous chiral condensate, the CDW as well as the real-kink crystal (RKC). Depending on the value of the diquark coupling we find a region of the phase diagram where the inhomogeneous chiral and the 2SC condensates coexist, confirming results of Refs. [1, 2]. Decreasing the diquark coupling favors the inhomogeneous phase over the coexistence phase. On the other hand, increasing the diquark coupling leads to a larger 2SC phase, while the inhomogeneous chiral and the coexistence phases become smaller. In agreement with previous studies the RKC Ansatz is energetically preferred over the CDW Ansatz. Both Ansätze lead to a qualitatively similar phase diagram, however the coexistence phase is smaller for the RKC Ansatz.

    hep-phPRD(2021)·28 citations
25. 25*

    Deep inelastic scattering on the quark-gluon plasma

    Tim Harris🇮🇹 · Harvey B. Meyer🇩🇪 · Arianna Toniato🇩🇪 · Marco Cè🇨🇭

    We provide an interpretation of the structure functions of a thermal medium such as the quark-gluon plasma in terms of the scattering of an incoming electron on the medium via the exchange of a spacelike photon. We then focus on the deep-inelastic scattering (DIS) regime, and formulate the corresponding moment sum rules obeyed by the structure functions. Accordingly, these moments are given by the thermal expectation value of twist-two operators, which is computable from first principles in lattice QCD for the first few moments. We also show how lattice QCD calculations can be used to probe how large the photon virtuality needs to be in order for the Bjorken scaling of structure functions to set in. Finally, we provide the parton-model interpretation of the structure functions in the Bjorken limit and test its consistency. As in DIS on the proton, the kinematic variable $x$ is proportional to the longitudinal momentum carried by the partons, however $x$ ranges from zero to infinity. Choosing the parton momentum parametrization to be $xTu$ where $u$ is the fluid four-velocity and $T$ its temperature in the rest frame, the parton distribution function for a plasma of non-interacting quarks is proportional to $x\log (1+e^{-x/2})$.

    hep-phhep-latJHEP(2021)·9 citations
26. 26*

    Understanding two slopes in the pp (p\bar p) differential cross sections

    Yu.A.Simonov🇷🇺

    Recent experiments have discovered two exponents in the $pp$ elastic differential cross sections with two different slope parameters, of the order $(16-20)$~GeV${}^{-2}$ and $(4-4.8)$~GeV${}^{-2}$ in the regions $-t\text{la}0.5$~GeV${}^2$ and $-t\text{ga}1$~GeV${}^2$, respectively. We suggest a simple model of the $pp$ elastic scattering with two types of particle exchanges: 1) when the exchanged particle transfers the momentum $\text{veQ}$ from a quark of the proton $p_1$ to one quark in another proton $p_2$, producing the slope $B_1$; 2) when the transfer occurs from two quarks in the $p_1$ to two quarks in the $p_2$, giving the exponent with the slope $B_2$. The resulting amplitude is proportional to the product of the form factors of two protons, depending on $\text{veQ}$, but with different coefficients in the cases 1) and 2). Using the only parameter - the proton charge radius $r_{ch}^2=0.93$~fm${}^2$, one obtains $B_1=16$~GeV${}^{-2}$,~$B_2=4$~GeV${}^{-2}$ with the strict value of the ratio, $\frac{B_1}{B_2}=4.0$, independent of $r_{ch}$. These predictions are surprisingly close to the data both in the $pp$ and in the $\bar{p}p$ differential cross sections. Comparison to experimental data and theoretical approaches is discussed, together with possible implications for the future development of the theory.

    hep-phhep-exJETP Lett.(2021)·2 citations
27. 27*

    The strongly intensive observable in pp collisions at LHC energies in the string fusion model

    V.V. Vechernin🇷🇺 · S.N. Belokurova🇷🇺

    The properties of the strongly intensive variable characterizing correlations between the number of particles in two separated rapidity interval in pp interactions at LHC energies are studied in the framework of the string fusion model. We perform the MC simulations of string distributions in the impact parameter plane to take into account the experimental conditions of pp collisions. We account the string fusion processes, leading to the formation of string clusters, embedding a finite lattice (a grid) in the impact parameter plane. As a result, we found the dependence of this variable both on the distance between the centers of the observation windows and their width for the minbias pp collisions at several initial energies. Analyzing these dependencies we can extract the important information on the properties of string clusters. We show that in pp collisions at LHC energies the string fusion effects have a significant impact on the behavior of this strongly intensive variable. The role of these effects is increasing with the initial energy and centrality of collisions. In particular, we found that the increase of this variable with initial energy takes place due to the growth of the portion of the fused string clusters in string configurations arising in pp interactions.

    hep-phnucl-thJ.Phys.Conf.Ser.(2020)·11 citations
28. 28*

    The Emergence of Electroweak Skyrmions through Higgs Bosons

    Juan Carlos Criado🇬🇧 · Valentin V. Khoze🇬🇧 · Michael Spannowsky🇬🇧

    Skyrmions are extended field configurations, initially proposed to describe baryons as topological solitons in an effective field theory of mesons. We investigate and confirm the existence of skyrmions within the electroweak sector of the Standard Model and study their properties. We find that the interplay of the electroweak sector with a dynamical Higgs field and the Skyrme term leads to a non-trivial vacuum structure with the skyrmion and perturbative vacuum sectors separated by a finite energy barrier. We identify dimension-8 operators that stabilise the electroweak skyrmion as a spatially localised soliton field configuration with finite size. Such operators are induced generically by a wide class of UV models. To calculate the skyrmion energy and radius we use a neural network method. Electroweak skyrmions are non-topological solitons but are exponentially long lived, and we find that the electroweak skyrmion is a viable dark matter candidate. While the skyrmion production cross section at collider experiments is suppressed, measuring the size of the Skyrme term in multi-Higgs-production processes at high-energy colliders is a promising avenue to probe the existence of electroweak skyrmions.

    hep-phhep-exhep-thJHEP(2021)·10 citations
29. 29*

    Impact of laser polarization on q-exponential photon tails in non-linear Compton scattering

    B. Kampfer🇩🇪 · A. I. Titov🇷🇺

    Non-linear Compton scattering of ultra-relativistic electrons traversing high-intensity laser pulses generates also hard photons. These photon high-energy tails are considered for parameters in reach at the forthcoming experiments LUXE and E-320. We consider the invariant differential cross sections $d\sigma /du$ between the IR and UV regions and analyze the impact of the laser polarization and find q-deformed exponential shapes. (The variable $u$ is the light-cone momentum-transfer from initial electron to final photon.) Optical laser pulses of various durations are compared with the monochromatic laser beam model which uncovers the laser intensity parameter in the range $\xi =1\cdots 10$. Some supplementary information is provided for the azimuthal final-electron/photon distributions and the photon energy-differential cross sections.

    hep-phPRA(2021)·13 citations
30. 30*

    Comments on gauge anomalies at dimension-six in the Standard Model Effective Field Theory

    Quentin Bonnefoy🇩🇪 · Luca Di Luzio🇩🇪 · Christophe Grojean🇩🇪 · Ayan Paul🇩🇪 · Alejo N. Rossia🇩🇪

    We study whether higher-dimensional operators in effective field theories, in particular in the Standard Model Effective Field Theory (SMEFT), can source gauge anomalies via the modification of the interactions involved in triangle diagrams. We find no evidence of such gauge anomalies at the level of dimension-6 operators that can therefore be chosen independently to each others without spoiling the consistency of SMEFT, at variance with recent claims. The underlying reason is that gauge-invariant combinations of Goldstone bosons and massive gauge fields are allowed to couple to matter currents which are not conserved. We show this in a toy model by computing the relevant triangle diagrams, as well as by working out Wess--Zumino terms in the bosonic EFT below all fermion masses. The same approach applies directly to the Standard Model both at the renormalisable level, providing a convenient and unusual way to check that the SM is anomaly free, as well as at the non-renormalisable level in SMEFT.

    hep-phhep-thJHEP(2021)·16 citations
31. 31*

    Vacuum structure of the ${\mathbb{Z}}_2$ symmetric Georgi-Machacek model

    Duarte Azevedo🇵🇹 · Pedro M. Ferreira🇬🇧 · Heather E. Logan🇨🇦 · Rui Santos🇵🇹

    We discuss the vacuum structure of a version of the Georgi-Machecek model with an exact ${\mathbb{Z}}_2$ symmetry acting on the triplet fields. Besides the usual custodial-symmetric model, with $\rho =1$ at tree-level, a model with a dark matter candidate is also viable. The other phases of the model lead to electric charge breaking, a wrong pattern of electroweak symmetry breaking or to $\rho \ne 1$ at tree-level. We derive conditions to have an absolute minimum in each of the two viable phases, the custodial and the dark matter phases.

    hep-phJHEP(2021)·14 citations
32. 32*

    Interpretation of LHCb Hidden-Charm Pentaquarks within the Compact Diquark Model

    Ahmed Ali🇩🇪 · Ishtiaq Ahmed🇵🇰 · M. Jamil Aslam🇵🇰 · Alexander Parkhomenko🇷🇺 · Abdur Rehman🇵🇰

    The LHCb collaboration have recently updated their analysis of the resonant $J/\psi p$ mass spectrum in the decay ${\Lambda }_b^0\to J/\psi p{K}^{-}$, making use of their combined Run~1 and Run~2 data. In the updated analysis, three narrow states, $P_c(4312{)}^{+}$, $P_c(4440{)}^{+}$, and $P_c(4457{)}^{+}$, are observed. The spin-parity assignments of these states are not yet known. We interpret these narrow resonances as compact hidden-charm diquark-diquark-antiquark pentaquarks. Using an effective Hamiltonian, based on constituent quarks and diquarks, we calculate the pentaquark mass spectrum for the complete $SU(3{)}_F$ lowest $S$- and $P$-wave multiplets, taking into account dominant spin-spin, spin-orbit, orbital and tensor interactions. The resulting spectrum is very rich and we work out the quark flavor compositions, masses, and $J^P$ quantum numbers of the pentaquarks. However, heavy quark symmetry restricts the observable states in ${\Lambda }_b$-baryon, as well as in the decays of the other weakly-decaying $b$-baryons, ${\Xi }_b$ and ${\Omega }_b$. In addition, some of the pentaquark states are estimated to lie below the $J/\psi p$ threshold in ${\Lambda }_b$-decays (and corresponding thresholds in ${\Xi }_b$- and ${\Omega }_b$-decays). They decay via $c\bar{c}$ annihilation into light hadrons or a dilepton pair, and are expected to be narrower than the $P_c$-states observed. We anticipate their discovery, as well as of the other pentaquark states present in the spectrum at the LHC, and in the long-term future at a Tera-$Z$ factory.

    hep-phhep-exPoS(2021)·13 citations
33. 33*

    Tetraquark Interpretation and Production Mechanism of the Belle $Y_b(10750)$-Resonance

    Ahmed Ali🇩🇪 · Luciano Maiani🇮🇹 · Alexander Parkhomenko🇷🇺 · Wei Wang🇨🇳

    Recently, the Belle Collaboration has updated the analysis of the cross sections for the processes $e^{+}{e}^{-}\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ ($n=1,2,3$) in the $e^{+}{e}^{-}$ center-of-mass energy range from 10.52 to 11.02~GeV. A new structure, called $Y_b(10750)$, with the mass $M(Y_b)=(10752.7\pm 5.9_{-1.1}^{+0.7})$~MeV and the Breit-Wigner width $\Gamma (Y_b)=(35.5_{-11.3-3.3}^{+17.6+3.9})$~MeV was observed. We interpret $Y_b(10750)$ as a compact $J^{PC}=1^{--}$ state with a dominant tetraquark component. The mass eigenstate $Y_b(10750)$ is treated as a linear combination of the diquark-antidiquark and $b\bar{b}$ components due to the mixing via gluonic exchanges shown recently to arise in the limit of large number of quark colors. The mixing angle between $Y_b$ and ${\rm Y}(5S)$ can be estimated from the electronic width, recently determined to be ${\Gamma }_{ee}(Y_b)=(13.7\pm 1.8)$~eV. The mixing provides a plausible mechanism for $Y_b(10750)$ production in high energy collisions from its $b\bar{b}$ component and we work out the Drell-Yan and prompt production cross sections for $pp\to Y_b(10750)\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ at the LHC. The resonant part of the dipion invariant mass spectrum in $Y_b(10750)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}$ and the corresponding angular distribution of ${\pi }^{+}$-meson in the dipion rest frame are presented.

    hep-phhep-exPoS(2021)·4 citations
34. 34*

    Octet and decuplet baryon self-energies in relativistic SU(3) chiral effective theory

    P. M. Copeland🇺🇸 · Chueng-Ryong Ji🇺🇸 · W. Melnitchouk🇺🇸

    The self-energies of the full set of flavor SU(3) octet and decuplet baryons are computed within a relativistic chiral effective theory framework. The leading nonanalytic chiral behavior is derived for the octet and decuplet masses, and a finite-range regularization consistent with Lorentz and gauge invariance is applied to account for the finite size of the baryons. Using a four-dimensional dipole form factor, the relative importance of various meson-baryon loop contributions to the self-energies is studied numerically as a function of the dipole range parameter and meson mass, and comparison is made between the relativistic results and earlier approximations within the heavy baryon limit.

    hep-phnucl-thPRD(2021)·5 citations
35. 35*

    Deep learning jet modifications in heavy-ion collisions

    Yi-Lun Du🇳🇴 · Daniel Pablos🇳🇴 · Konrad Tywoniuk🇳🇴

    Jet interactions in a hot QCD medium created in heavy-ion collisions are conventionally assessed by measuring the modification of the distributions of jet observables with respect to the proton-proton baseline. However, the steeply falling production spectrum introduces a strong bias toward small energy losses that obfuscates a direct interpretation of the impact of medium effects in the measured jet ensemble. Modern machine learning techniques offer the potential to tackle this issue on a jet-by-jet basis. In this paper, we employ a convolutional neural network (CNN) to diagnose such modifications from jet images where the training and validation is performed using the hybrid strong/weak coupling model. By analyzing measured jets in heavy-ion collisions, we extract the original jet transverse momentum, i.e., the transverse momentum of an identical jet that did not pass through a medium, in terms of an energy loss ratio. Despite many sources of fluctuations, we achieve good performance and put emphasis on the interpretability of our results. We observe that the angular distribution of soft particles in the jet cone and their relative contribution to the total jet energy contain significant discriminating power, which can be exploited to tailor observables that provide a good estimate of the energy loss ratio. With a well-predicted energy loss ratio, we study a set of jet observables to estimate their sensitivity to bias effects and reveal their medium modifications when compared to a more equivalent jet population, i.e., a set of jets with similar initial energy. Finally, we also show the potential of deep learning techniques in the analysis of the geometrical aspects of jet quenching such as the in-medium traversed length or the position of the hard scattering in the transverse plane, opening up new possibilities for tomographic studies.

    hep-phJHEP(2020)·62 citations
36. 36*

    The mono-Higgs + MET signal at the Large Hadron Collider: a study on the $\gamma \gamma$ and $b\bar{b}$ final states

    Debabrata Bhowmik🇮🇳 · Jayita Lahiri🇮🇳 · Satyaki Bhattacharya🇮🇳 · Biswarup Mukhopadhyaya🇮🇳 · Ritesh K Singh🇮🇳

    We investigate the potential of the channel {\em mono-Higgs + MET} in yielding signals of dark mater at the high-luminosity Large Hadron Collider (LHC). As illustration, a scalar dark matter in a Higgs portal scenario has been chosen, whose phenomenological viability has been ensured by postulating the existence of dimension-6 operators that enable cancellation in certain amplitudes for elastic scattering of dark matter in direct search experiments. These operators are found to have non-negligible contribution to the mono-Higgs signal. Thereafter, we carry out a detailed analysis of this signal, with the accompanying MET providing a useful handle in suppressing backgrounds. Signals for the Higgs decaying into both the diphoton and $b\bar{b}$ channels have been studied. A cut-based simulation is presented first, followed by a demonstration of how the statistical significance can be improved through analyses based on Boosted Decision Trees and Artificial Neural Network. The improvement is found to be especially noticeable for the $b\bar{b}$ channel.

    hep-phhep-exEPJC(2022)·9 citations
37. 37*

    STrEAMlining EFT Matching

    Timothy Cohen🇺🇸 · Xiaochuan Lu🇺🇸 · Zhengkang Zhang🇺🇸

    This paper presents STrEAM (SuperTrace Evaluation Automated for Matching), a Mathematica package that calculates all functional supertraces which arise when matching a generic UV model onto a relativistic Effective Field Theory (EFT) at one loop and to arbitrary order in the heavy mass expansion. STrEAM implements the covariant derivative expansion to automate the most tedious step of the streamlined functional matching prescription presented in arXiv:2011.02484 . The code and an example notebook are available at https://www.github.com/EFTMatching/STrEAM .

    hep-phhep-thSciPost Phys.(2021)·79 citations
38. 38*

    TMD Fragmentation Functions at N${}^3$LO

    Markus A. Ebert🇺🇸 · Bernhard Mistlberger🇺🇸 · Gherardo Vita🇺🇸

    We compute the unpolarized quark and gluon transverse-momentum dependent fragmentation functions (TMDFFs) at next-to-next-to-next-to-leading order (N${}^3$LO) in perturbative QCD. The calculation is based on a relation between the TMDFF and the limit of the semi-inclusive deep inelastic scattering cross section where all final-state radiation becomes collinear to the detected hadron. The required cross section is obtained by analytically continuing our recent computation of the Drell-Yan and Higgs boson production cross section at N${}^3$LO expanded around the limit of all final-state radiation becoming collinear to one of the initial states. Our results agree with a recent independent calculation by Luo et al.

    hep-phnucl-thJHEP(2021)·62 citations
39. 39*

    The Energy-Energy Correlation in the back-to-back limit at N${}^3$LO and N${}^3$LL${}^{\prime }$

    Markus A. Ebert🇺🇸 · Bernhard Mistlberger🇺🇸 · Gherardo Vita🇺🇸

    We present the analytic formula for the Energy-Energy Correlation (EEC) in electron-positron annihilation computed in perturbative QCD to next-to-next-to-next-to-leading order (N${}^3$LO) in the back-to-back limit. In particular, we consider the EEC arising from the annihilation of an electron-positron pair into a virtual photon as well as a Higgs boson and their subsequent inclusive decay into hadrons. Our computation is based on a factorization theorem of the EEC formulated within Soft-Collinear Effective Theory (SCET) for the back-to-back limit. We obtain the last missing ingredient for our computation - the jet function - from a recent calculation of the transverse-momentum dependent fragmentation function (TMDFF) at N${}^3$LO. We combine the newly obtained N${}^3$LO jet function with the well known hard and soft function to predict the EEC in the back-to-back limit. The leading transcendental contribution of our analytic formula agrees with previously obtained results in $\mathcal{N}=4$ supersymmetric Yang-Mills theory. We obtain the $N=2$ Mellin moment of the bulk region of the EEC using momentum sum rules. Finally, we obtain the first resummation of the EEC in the back-to-back limit at N${}^3$LL${}^{\prime }$ accuracy, resulting in a factor of $\sim 4$ reduction of uncertainties in the peak region compared to N${}^3$LL predictions.

    hep-phhep-thnucl-thJHEP(2021)·81 citations
40. 40*

    Probing naturally light singlets with a displaced vertex trigger

    Yuri Gershtein🇺🇸 · Simon Knapen🇨🇭 · Diego Redigolo🇨🇭

    We investigate the physics case for a dedicated trigger on a low mass, hadronic displaced vertex at the high luminosity LHC, relying on the CMS phase II track trigger. We estimate the trigger efficiency with a simplified simulation of the CMS track trigger and show that the L1 trigger rate from fake vertices, B meson decays and secondary interactions with the detector material can likely be brought down to the kHz level with a minimal set of cuts. While it would with any doubt be a severe experimental challenge to implement, we conclude that a displaced vertex trigger could open qualitatively new parameter space for exotic Higgs decays, exotic B decays and even direct production of light resonances. We parametrize the physics potential in terms of a singlet scalar mixing with the Standard Model Higgs and an axion-like particle with a coupling to gluons, and review a number or relevant models motivated by the hierarchy and strong CP problems, dark matter and baryogenesis.

    hep-phPLB(2021)·61 citations
41. 41*

    IceCube constraints on Violation of Equivalence Principle

    Damiano F. G. Fiorillo🇮🇹 · Gianpiero Mangano🇮🇹 · Stefano Morisi🇮🇹 · Ofelia Pisanti🇮🇹

    Among the information provided by high energy neutrinos, a promising possibility is to analyze the effects of a Violation of Equivalence Principle (VEP) on neutrino oscillations. We analyze the recently released IceCube data on atmospheric neutrino fluxes under the assumption of a VEP and obtain updated constraints on the parameter space with the benchmark choice that neutrinos with different masses couple with different strengths to the gravitational field. In this case we find that the VEP parameters times the local gravitational potential at Earth can be constrained at the level of $10^{-27}$. We show that the constraints from atmospheric neutrinos strongly depend on the assumption that the neutrino eigenstates interacting diagonally with the gravitational field coincide with the mass eigenstates, which is not \textit{a priori} justified: this is particularly clear in the case that the basis of diagonal gravitational interaction coincide with the flavor basis, which cannot be constrained by the observation of atmospheric neutrinos. Finally, we quantitatively study the effect of a VEP on the flavor composition of the astrophysical neutrinos, stressing again the interplay with the basis in which the VEP is diagonal: we find that for some choices of such basis the flavor ratio measured by IceCube can significantly change.

    hep-phastro-ph.HEgr-qchep-ex+1JCAP(2021)·19 citations
42. 42*

    How to GAN Event Unweighting

    Mathias Backes🇩🇪 · Anja Butter🇩🇪 · Tilman Plehn🇩🇪 · Ramon Winterhalder🇩🇪

    Event generation with neural networks has seen significant progress recently. The big open question is still how such new methods will accelerate LHC simulations to the level required by upcoming LHC runs. We target a known bottleneck of standard simulations and show how their unweighting procedure can be improved by generative networks. This can, potentially, lead to a very significant gain in simulation speed.

    hep-phSciPost Phys.(2021)·46 citations
43. 43*

    Nonminimal Lorentz Violation in Macroscopic Matter

    Matthew Mewes🇺🇸

    The effects of Lorentz and CPT violations on macroscopic objects are explored. Effective composite coefficients for Lorentz violation are derived in terms of coefficients for electrons, protons, and neutrons in the Standard-Model Extension, including all minimal and nonminimal violations. The hamiltonian and modified Newton's second law for a test body are derived. The framework is applied to free-fall and torsion-balance tests of the weak equivalence principle and to orbital motion. The effects on continuous media are studied, and the frequency shifts in acoustic resonators are calculated.

    hep-phSymmetry(2020)·2 citations
44. 44*

    Experimental QCD summary (ICHEP 2020)

    David d'Enterria🇨🇭

    This writeup summarizes the main experimental studies of the strong interaction, theoretically described by quantum chromodynamics (QCD), that were presented during the ICHEP-2020 conference. The latest results, measured mostly in p-p collisions at the LHC, are categorized in seven broad topics: (i) Extractions of the strong coupling constant ${\alpha }_s(m_{\mathrm{Z}})$; (ii) Comparison of data to fixed-order (N${}^{\mathrm{n}}$LO) perturbative QCD calculations; (iii) Determinations of parton distribution functions (PDFs); (iv) Comparison of data to resummed (N${}^{\mathrm{n}}$LL) pQCD calculations; (v) Parton showering and jet substructure analyses; (vi) Semihard (double parton interactions, multiparton interactions, hard diffraction), and soft (elastic and diffractive) QCD scatterings; and (vii) Studies of parton hadronization in ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and p-p collisions.

    ↳ hep-exhep-phPoS(2021)·3 citations
45. 45*

    Quintessential inflation in Palatini $f(R)$ gravity

    Konstantinos Dimopoulos🇬🇧 · Samuel Sánchez López🇬🇧

    We investigate in detail a family of quintessential inflation models in the context of $R+R^2$ Palatini modified gravity. We find that successful inflation and quintessence are obtained with an inflaton scalar potential that is approximately quadratic in inflation and inverse quartic in quintessence. We show that corrections for the kination period due to Palatini modified gravity are subdominant, while the setup does not challenge constraints on modified gravity from solar system observations and microscopic experiments, in contrast to the metric case. We obtain concrete predictions regarding primordial tensors, to be probed in the near future.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2021)·47 citations
46. 46*

    Review of Atmospheric Neutrino Results from Super-Kamiokande

    Volodymyr Takhistov (for the Super-Kamiokande Collaboration)🇺🇸

    While neutrino physics enters precision era, several important unknowns remain. Atmospheric neutrinos allow to simultaneously test key oscillation parameters, with Super-Kamiokande experiment playing a central role. We discuss results from atmospheric neutrino oscillation analysis of the full dataset from Super-Kamiokande I-IV phases. Further, we discuss tests of non-standard neutrino interactions with atmospheric neutrinos in Super-Kamiokande.

    ↳ hep-exastro-ph.HEhep-phPoS(2021)·12 citations
47. 47*

    Lagrangian formulation for an extended cosmological equation-of-state

    Grigoris Panotopoulos🇵🇹 · Ilidio Lopes🇵🇹 · Angel Rincon🇨🇱

    We show that the extended cosmological equation-of-state developed starting from a Chaplygin equation-of-state, recently applied to stellar modeling, is a viable dark energy model consistent with standard scalar potentials. Moreover we find a Lagrangian formulation based on a canonical scalar field with the appropriate self-interaction potential. Finally, we fit the scalar potential obtained numerically with concrete functions well studied in the literature. Our results may be of interest to model builders and particle physicists.

    ↳ gr-qcastro-ph.COhep-phPhys.Dark Univ.(2021)·11 citations
48. 48*

    The QCD Axion and Gravitational Waves in light of NANOGrav results

    Nicklas Ramberg🇩🇪 · Luca Visinelli🇮🇹

    The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration has recently reported strong evidence for a stochastic process affecting the 12.5 yr dataset of pulsar timing residuals. We show that the signal can be interpreted in terms of a stochastic gravitational wave background emitted from a network of axionic strings in the early Universe. The spontaneous breaking of the Peccei-Quinn symmetry originate the axionic string network and the QCD axion, the dark matter particle in the model. We explore a non-standard cosmological model driven by an exotic scalar field $\varphi$ which evolves under the influence of a self-interacting potential; the axion field starts to oscillate during the modified cosmology, and provides the dark matter observed. For an equation of state $w_{\varphi }<1/3$, the QCD axion mass is smaller than expected in the standard cosmology and the GW spectrum from axionic strings is larger. We assess the parameter space of the model which is consistent with the NANOGrav-$12.5$yr detection, which can be explained within 95\% limit by a QCD axion field evolving in a dust-like scenario, as well as within 68\% limit in a cosmology with $w_{\varphi }<0$.

    ↳ astro-ph.COhep-phPRD(2021)·35 citations
49. 49*

    Status of the MUonE experiment

    Giovanni Abbiendi🇮🇹

    The MUonE experiment aims at an independent and very precise determination of the leading hadronic contribution to the muon magnetic moment, based on an alternative method, complementary to the existing ones. This can be achieved by measuring with unprecedented precision the shape of the differential cross section of $\mu e$ elastic scattering, using the intense muon beam available at CERN, with energy of 150 GeV, off atomic electrons of a light target. The status of the project is presented, with recent results in preparation for the test run scheduled in 2021 with a reduced detector.

    ↳ hep-exhep-phphysics.ins-detPoS(2021)·11 citations
50. 50*

    Using LSST Microlensing to Constrain Dark Compact Objects in Spherical and Disk Configurations

    Harrison Winch🇨🇦 · Jack Setford🇨🇦 · Jo Bovy🇨🇦 · David Curtin🇨🇦

    The Legacy Survey of Space and Time (LSST) with the Vera Rubin Observatory will provide strong microlensing constraints on dark compact objects (DCOs) in our Galaxy. However, most current forecasts limit their analysis to Primordial Black Holes (PBH). It is unclear how well LSST microlensing will be able to constrain alternative models of DCOs with different Galactic spatial profile distributions at a subdominant DM fraction. In this work, we investigate how well LSST microlensing will constrain spherical or disk-like Galactic spatial distributions of DCOs, taking into account extended observing times, baryonic microlensing background, and sky distribution of LSST sources. These extensions represent significant improvements over existing microlensing forecasts in terms of both accuracy and versatility. We demonstrate this power by deriving new LSST sensitivity projections for DCOs in spherical and disk-like distributions. We forecast that LSST will be able to constrain one solar mass PBHs to have a DM fraction under $4.1\times 10^{-4}$. One-solar-mass objects in a dark disk distribution with the same dimensions as the Galactic disk will be constrained below $3.1\times 10^{-4}$, while those with $m=10^5{M}_{\odot }$ will be constrained to below $3.4\times 10^{-5}$. We find that compressed dark disks can be constrained up to a factor of $\sim 10$ better than ones with identical dimensions to the baryonic disk. We also find that dark disks become less tightly constrained when they are tilted with respect to our own disk. This forecasting software is a versatile tool, capable of constraining any model of DCOs in the Milky Way with microlensing, and is made publically available at {https://github.com/HarrisonWinch96/DarkDisk_Microlensing}.

    ↳ astro-ph.GAastro-ph.COhep-phApJ(2022)·28 citations
51. 51*

    Emergence of oscillons in kink-impurity interactions

    Mariya Lizunova🇳🇱 · Jasper Kager🇳🇱 · Stan de Lange🇳🇱 · Jasper van Wezel🇳🇱

    The (1+1)-dimensional classical ${\phi }^4$ theory contains stable, topological excitations in the form of solitary waves or kinks, as well as stable but non-topological solutions, such as the oscillon. Both are used in effective descriptions of excitations throughout myriad fields of physics. The oscillon is well-known to be a coherent, particle-like solution when introduced as an Ansatz in the ${\phi }^4$ theory. Here, we show that oscillons also arise naturally in the dynamics of the theory, in particular as the result of kink-antikink collisions in the presence of an impurity. We show that in addition to the scattering of kinks and the formation of a breather, both bound oscillon pairs and propagating oscillons may emerge from the collision. We discuss their resonances and critical velocity as a function of impurity strength and highlight the role played by the impurity in the scattering process.

    ↳ cond-mat.otherhep-phnlin.PSJ.Phys.A(2021)·4 citations
52. 52*

    Spectral distortion constraints on photon injection from low-mass decaying particles

    Boris Bolliet🇬🇧 · Jens Chluba🇬🇧 · Richard Battye🇬🇧

    Spectral distortions (SDs) of the cosmic microwave background (CMB) provide a powerful tool for studying particle physics. Here we compute the distortion signals from decaying particles that convert directly into photons at different epochs during cosmic history, focusing on injection energies $E_{\mathrm{inj}}\lesssim 20\mathrm{keV}$. We deliver a comprehensive library of SD solutions that can be used to study a wide range of particle physics scenarios. We use {\tt CosmoTherm} to compute the SD signals, including effects on the ionization history and opacities of the Universe. We also consider the effect of blackbody-induced stimulated decay, which can modify the injection history significantly. Then, we use data from COBE/FIRAS and EDGES to constrain the properties of the decaying particles. We explore scenarios where these provide a dark matter (DM) candidate or constitute only a small fraction of DM. We complement the SD constraints with CMB anisotropy constraints, highlighting new effects from injections at very-low photon energies ($h\nu \lesssim 10^{-4}\mathrm{eV}$). Our model-independent constraints exhibit rich structures in the lifetime-energy domain, covering injection energies $E_{\mathrm{inj}}\simeq 10^{-10}\mathrm{eV}-10\mathrm{keV}$ and lifetimes ${\tau }_X\simeq 10^5\mathrm{s}-10^{33}\mathrm{s}$. We discuss the constraints on axions and axion-like particles that convert directly into two photons, revising existing SD constraints in the literature. Our limits are competitive with other constraints for axion masses $m_a{c}^2\gtrsim 27\mathrm{eV}$ and we find that simple estimates based on the overall energetics are generally inaccurate. Future CMB spectrometers could significantly improve the obtained constraints, thus providing an important complementary probe of early-universe particle physics.

    ↳ astro-ph.COhep-phMNRAS(2021)·102 citations
53. 53*

    Warm-assisted natural inflation

    Yakefu Reyimuaji🇨🇳 · Xinyi Zhang🇨🇳

    We consider natural inflation in a warm inflation framework with a temperature-dependent dissipative coefficient $\Gamma \propto T^3$. Natural inflation can be compatible with the Planck 2018 results with such warm assistance. With no a priori assumptions on the dissipative effect's magnitude, we find that the Planck results prefer a weak dissipative regime for our benchmark scale $f=5M_{\mathrm{pl}}$, which lies outside the $2\sigma$ region in the cold case. The inflation starts in the cold regime and evolves with a growing thermal fluctuation that dominates over quantum fluctuation before the end of the inflation. The observed spectral tilt puts stringent constraints on the model's parameter space. We find that $f<1M_{\mathrm{pl}}$ is excluded. A possible origin of such dissipative coefficient from axion-like coupling to gauge fields and tests of the model are also discussed.

    ↳ astro-ph.COhep-phJCAP(2021)·30 citations
54. 54*

    Multifarious roles of hidden chiral-scale symmetry:"Quenching" $g_A$ in nuclei

    Mannque Rho🇫🇷

    I discuss how the axial current coupling constant $g_A$ renormalized in scale symmetric chiral EFT defined at a chiral matching scale impacts on the axial current matrix elements on beta decays in nuclei with and without neutrinos. The "quenched" $g_A$ observed in nuclear superallowed Gamow-Teller transitions, a long-standing puzzle in nuclear physics, is shown to encode the emergence of chiral-scale symmetry hidden in QCD in the vacuum. This enables one to explore how trace-anomaly-induced scale symmetry breaking enters in the renormalized $g_A$ in nuclei applicable to certain non-unique forbidden processes involved in neutrinoless double beta decays. A parallel is made between the roles of chiral-scale symmetry in quenching $g_A$ in highly dense medium and in hadron-quark continuity in the EoS of dense matter in massive compact stars. A systematic chiral-scale EFT, presently lacking in nuclear theory and potentially crucial for the future progress, is suggested as a challenge in the field.

    ↳ nucl-thhep-phSymmetry(2021)·7 citations
55. 55*

    Updated constraints on massive neutrino self-interactions from cosmology in light of the $H_0$ tension

    Shouvik Roy Choudhury🇮🇳 · Steen Hannestad🇩🇰 · Thomas Tram🇩🇰

    We have updated the constraints on flavour universal neutrino self-interactions mediated by a heavy scalar, in the effective 4-fermion interaction limit. We use the relaxation time approximation to modify the collisional neutrino Boltzmann equations, which is known to be very accurate for this particular scenario. Based on the latest CMB data from the Planck 2018 data release as well as auxiliary data we confirm the presence of a region in parameter space with relatively strong self-interactions which provides a better than naively expected fit. However, we also find that the most recent data, in particular high-$\ell$ polarisation data from the Planck 2018 release, disfavours this solution even though it cannot yet be excluded. Our analysis takes into account finite neutrino masses (parameterised in terms of $\sum m_{\nu }$) and allows for a varying neutrino energy density (parameterised in terms of $N_{\mathrm{eff}}$), and we find that in all cases the neutrino mass bound inferred from cosmological data is robust against the presence of neutrino self-interactions. Finally, we also find that the strong neutrino self-interactions do not lead to a high value of $H_0$ being preferred, i.e.\ this model is not a viable solution to the current $H_0$ discrepancy.

    ↳ astro-ph.COhep-phJCAP(2021)·138 citations
56. 56*

    Role of baryon resonances in the ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ reaction within an effective-Lagrangian model

    Miklós Zétényi🇭🇺 · Deniz Nitt🇩🇪 · Michael Buballa🇩🇪 · Tetyana Galatyuk🇩🇪

    We present a study of the reaction ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ for $\sqrt{s}=1.49\text{GeV}$, including non-resonant Born terms and contributions of the $N(1440)$, $N(1520)$, $N(1535)$ resonances ($R$), using an effective-Lagrangian model, which we extended by a phenomenological phase factor at the $RN\rho$ vertex function. We give predictions for both the differential cross section $d\sigma /dm$ and the spin density matrix elements of the virtual photon that decays into the lepton pair. In the studied energy range, the cross section is dominated by the Born and $N(1520)$ contributions.

    ↳ nucl-thhep-phPRC(2021)·9 citations
57. 57*

    Limits on Clustering and Smooth Quintessence from the EFTofLSS

    Guido D'Amico🇮🇹 · Yaniv Donath🇨🇭 · Leonardo Senatore🇺🇸 · Pierre Zhang🇨🇳

    We apply the Effective Field Theory of Large-Scale Structure (EFTofLSS) to analyze cosmological models with clustering quintessence, which allows us to consistently describe the parameter region in which the quintessence equation of state $w<-1$. First, we extend the description of biased tracers in redshift space to the presence of clustering quintessence, and compute the one-loop power spectrum. We solve the EFTofLSS equations using the exact time dependence, which is relevant to obtain unbiased constraints. Then, fitting the full shape of BOSS pre-reconstructed power spectrum measurements, the BOSS post-reconstruction BAO measurements, BAO measurements from 6DF/MGS and eBOSS, the Supernovae from Pantheon, and a prior from BBN, we bound the clustering quintessence equation of state parameter $w=-1.011_{-0.048}^{+0.053}$ at $68\%$ C.L.. Further combining with Planck, we obtain $w=-1.028_{-0.030}^{+0.037}$ at $68\%$ C.L.. We also obtain constraints on smooth quintessence, in the physical regime $w\ge -1$: combining all datasets, we get $-1\le w<-0.979$ at $68\%$ C.L.. These results strongly support a cosmological constant.

    ↳ astro-ph.COhep-phhep-thJCAP(2024)·63 citations
58. 58*

    Global $\Lambda$ polarization in moderately relativistic nuclear collisions

    Yu. B. Ivanov🇷🇺

    Predictions for the global polarization of $\Lambda$ hyperons in Au+Au collisions at moderately relativistic collision energies, 2.4 $\le \sqrt{s_{NN}}\le$ 11 GeV, are made. These are based on the thermodynamic approach to the global polarization incorporated into the model of the three-fluid dynamics. Centrality dependence of the polarization is studied. It is predicted that the polarization reaches a maximum or a plateau (depending on the equation of state and centrality) at $\sqrt{s_{NN}}\approx$ 3 GeV. It is found that the global polarization increases with increasing width of the rapidity window around the midrapidity.

    ↳ nucl-thhep-phnucl-exPRC(2021)·54 citations
59. 59*

    A scattering amplitudes approach to hard thermal loops

    Leonardo de la Cruz🇮🇹

    Inspired by recent progress on classical limits of scattering amplitudes, we show that hard thermal loops can be obtained from classical limits of off-shell currents. The classicality of hard thermal loops is made manifest by associating classical wavenumbers to soft particles. We compute the classical limit of these currents in QED, QCD and gravity. Our proposal does not involve the introduction of ghosts.

    ↳ hep-thhep-phPRD(2021)·22 citations
60. 60*

    Chemical potential on the lattice: Universal or Unique?

    Rajiv V. Gavai🇩🇪

    Lattice techniques are the most reliable ones to investigate non-perturbative aspects of quantum chromodynamics (QCD) such as its phase diagram in the temperature-baryon density plane. They are, however, well-known to be beset with a variety of problems as one increases the density. We address here the old question of placing the baryonic (quark) chemical potential on the lattice. We point out that it may have important consequences for the current and future experimental searches of QCD critical point.

    ↳ hep-lathep-phnucl-th1 citation
61. 61*

    Gravitational waves from colliding vacuum bubbles in gauge theories

    Marek Lewicki🇵🇱 · Ville Vaskonen🇪🇸

    We study production of gravitational waves (GWs) in strongly supercooled cosmological phase transitions in gauge theories. We extract from two-bubble lattice simulations the scaling of the GW source, and use it in many-bubble simulations in the thin-wall limit to estimate the resulting GW spectrum. We find that in presence of the gauge field the GW source decays with bubble radius as $\propto R^{-3}$ after collisions. This leads to a GW spectrum that follows ${\Omega }_{\mathrm{GW}}\propto {\omega }^{2.3}$ at low frequencies and ${\Omega }_{\mathrm{GW}}\propto {\omega }^{-2.4}$ at high frequencies, marking a significant deviation from the popular envelope approximation.

    ↳ astro-ph.COhep-phEPJC(2021)·119 citations
62. 62*

    Minkowski Box from Yangian Bootstrap

    Luke Corcoran🇩🇪 · Florian Loebbert🇩🇪 · Julian Miczajka🇩🇪 · Matthias Staudacher🇩🇪

    We extend the recently developed Yangian bootstrap for Feynman integrals to Minkowski space, focusing on the case of the one-loop box integral. The space of Yangian invariants is spanned by the Bloch-Wigner function and its discontinuities. Using only input from symmetries, we constrain the functional form of the box integral in all 64 kinematic regions up to twelve (out of a priori 256) undetermined constants. These need to be fixed by other means. We do this explicitly, employing two alternative methods. This results in a novel compact formula for the box integral valid in all kinematic regions of Minkowski space.

    ↳ hep-thhep-phmath-phmath.MPJHEP(2021)·22 citations
63. 63*

    Constraints on discrete global symmetries in quantum gravity

    Passant Ali🇩🇪 · Astrid Eichhorn🇩🇰 · Martin Pauly🇩🇪 · Michael M. Scherer🇩🇪

    The question whether global symmetries can be realized in quantum-gravity-matter-systems has far-reaching phenomenological consequences. Here, we collect evidence that within an asymptotically safe context, discrete global symmetries of the form ${\mathbb{Z}}_n$, $n>4$, cannot be realized in a near-perturbative regime. In contrast, an effective-field-theory approach to quantum gravity might feature such symmetries, providing a mechanism to generate mass hierarchies in the infrared without the need for additional fine-tuning.

    ↳ gr-qchep-phhep-thJHEP(2021)·20 citations
64. 64*

    Impact of a Midband Gravitational Wave Experiment On Detectability of Cosmological Stochastic Gravitational Wave Backgrounds

    Barry C. Barish🇺🇸 · Simeon Bird🇺🇸 · Yanou Cui🇺🇸

    We make forecasts for the impact a future "midband" space-based gravitational wave experiment, most sensitive to $10^{-2}-10$ Hz, could have on potential detections of cosmological stochastic gravitational wave backgrounds (SGWBs). Specific proposed midband experiments considered are TianGo, B-DECIGO and AEDGE. We propose a combined power-law integrated sensitivity (CPLS) curve combining GW experiments over different frequency bands, which shows the midband improves sensitivity to SGWBs by up to two orders of magnitude at $10^{-2}-10$ Hz. We consider GW emission from cosmic strings and phase transitions as benchmark examples of cosmological SGWBs. We explicitly model various astrophysical SGWB sources, most importantly from unresolved black hole mergers. Using Markov Chain Monte Carlo, we demonstrated that midband experiments can, when combined with LIGO A+ and LISA, significantly improve sensitivities to cosmological SGWBs and better separate them from astrophysical SGWBs. In particular, we forecast that a midband experiment improves sensitivity to cosmic string tension $G\mu$ by up to a factor of $10$, driven by improved component separation from astrophysical sources. For phase transitions, a midband experiment can detect signals peaking at $0.1-1$ Hz, which for our fiducial model corresponds to early Universe temperatures of $T_{\ast }\sim 10^4-10^6$ GeV, generally beyond the reach of LIGO and LISA. The midband closes an energy gap and better captures characteristic spectral shape information. It thus substantially improves measurement of the properties of phase transitions at lower energies of $T_{\ast }\sim O(10^3)$ GeV, potentially relevant to new physics at the electroweak scale, whereas in this energy range LISA alone will detect an excess but not effectively measure the phase transition parameters. Our modelling code and chains are publicly available.

    ↳ gr-qcastro-ph.COhep-exhep-ph+1PRD(2021)·21 citations
65. 65*

    Application of Regge-theory to astronomical objects

    G. G. Adamian🇷🇺 · N. V. Antonenko🇷🇺 · H. Lenske🇩🇪 · V. V. Sargsyan🇷🇺

    Using the model based on the Regge-like laws, new analytical formulas are obtained for the moment of inertia, the rotation frequency, and the radius of astronomical non-exotic objects (planets, stars, galaxies, and clusters of galaxies). The rotation frequency and moment of inertia of neutron star and the observable Universe are estimated. The estimates of the average numbers of stars and galaxies in the observable Universe are given. The Darwin instability effect in the binary systems (di-planets, di-stars, and di-galaxies) is also analyzed.

    ↳ physics.class-phastro-ph.SRgr-qchep-phMDPI Physics(2021)·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.