Fri·Jun 26, 2020Friday·June 26, 2020

1. 01*

   Symmetries and their breaking in the fundamental laws of physics

   Jose Bernabeu🇪🇸

   Symmetries in the Physical Laws of Nature lead to observable effects. Beyond regularities and conserved magnitudes, the last decades in Particle Physics have seen the identification of symmetries, and their well defined breaking, as the guiding principle for the elementary constituents of matter and their interactions. Flavour SU(3) symmetry of hadrons led to the Quark Model and the antisymmetry requirement under exchange of identical fermions led to the colour degree of freedom, the charge for the interactions of quarks and gluons in the SU(3) local gauge symmetry. Parity Violation in weak interactions led to consider the Chiral Fields with definite transformation properties under the weak isospin gauge group of the ElectroWeak SU(2)xU(1) Symmetry, which predicted novel weak neutral current interactions. CP-Violation led to three families of quarks opening the field of Flavour Physics. Time-Reversal-Violation has been observed with Entangled neutral mesons, compatible with CPT-invariance. The cancellation of gauge anomalies leads to Quark-Lepton Symmetry. Neutrinos were postulated to save energy and angular momentum conservation in beta decay. The discovery of neutrino oscillations led to a new era about their origin of mass, mixing, discrete symmetries and the global lepton-number violation. Leptogenesis may be the source of the matter-antimatter asymmetry in the Universe. The discovery of quarks and leptons and the mediators of their interactions, with observables in spectacular agreement with this Standard Theory, is the triumph of Symmetries. Gauge symmetry is exact only when the particles are massless. One needs a subtle breaking of the symmetry, providing the Origin of Mass, without affecting the interactions: the Brout-Englert-Higgs Mechanism which produces the Higgs Boson as a remnant. Open present problems are addressed with the search of New Physics Beyond-the-Standard-Model.

   hep-phSymmetry(2020)·3 citations
2. 02*

   Higgs modulation of emergent mass as revealed in kaon and pion parton distributions

   Zhu-Fang Cui🇨🇳 · Minghui Ding🇮🇹 · Fei Gao🇩🇪 · Khepani Raya🇨🇳 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Craig D. Roberts🇨🇳 · Jose Rodriguez-Quintero🇪🇸 · Sebastian M. Schmidt🇩🇪

   Strangeness was discovered roughly seventy years ago, lodged in a particle now known as the kaon, $K$. Kindred to the pion, $\pi$; both states are massless in the absence of Higgs-boson couplings. Kaons and pions are Nature's most fundamental Nambu-Goldstone modes. Their properties are largely determined by the mechanisms responsible for emergent mass in the standard model, but modulations applied by the Higgs are crucial to Universe evolution. Despite their importance, little is known empirically about $K$ and $\pi$ structure. This study delivers the first parameter-free predictions for all $K$ distribution functions (DFs) and comparisons with the analogous $\pi$ distributions, i.e. the one-dimensional maps that reveal how the light-front momentum of these states is shared amongst the gluons and quarks from which they are formed. The results should stimulate improved analyses of existing data and motivate new experiments sensitive to all $K$ and $\pi$ DFs.

   hep-phhep-exhep-latnucl-ex+1EPJA(2021)·54 citations
3. 03*

   Electric But Not Eclectic: Thermal Relic Dark Matter for the XENON1T Excess

   Joseph Bramante🇨🇦 · Ningqiang Song🇨🇦

   The identity of dark matter is being sought with increasingly sensitive and voluminous underground detectors. Recently the XENON1T collaboration reported excess electronic recoil events, with most of these having recoil energies around $1-30$ keV. We show that a straightforward model of inelastic dark matter produced via early universe thermal freeze-out annihilation can account for the XENON1T excess. Remarkably, this dark matter model consists of a few simple elements: sub-GeV mass Dirac fermion dark matter coupled to a lighter dark photon kinetically mixed with the Standard Model photon. A scalar field charged under the dark U(1) gauge symmetry can provide a mass for the dark photon and splits the Dirac fermion component state masses by a few keV, which survive in equal abundance and interact inelastically with electrons and nuclei.

   hep-phastro-ph.COhep-exPRL(2020)·79 citations
4. 04*

   Novel dynamic critical phenomena induced by superfluidity and the chiral magnetic effect in Quantum Chromodynamics

   Noriyuki Sogabe🇯🇵

   In this thesis, we study the novel dynamic critical phenomena induced by superfluidity and the chiral magnetic effect in Quantum Chromodynamics (QCD), respectively. In particular, we find the new dynamic universality class of the high-density QCD critical point between the nuclear and quark superfluid phases beyond the conventional Hohnenberg and Halperin's classification. We also consider the second-order chiral phase transition under an external magnetic field and find that the inclusion of the chiral magnetic effect changes the dynamic universality class from the model E into model A within the conventional classification.

   hep-phhep-thnucl-th0 citations
5. 05*

   Spin and flavor projection operators in the $SU(2N_f)$ spin-flavor group

   Victor Miguel Banda Guzman🇲🇽 · Ruben Flores-Mendieta🇲🇽 · Johann Hernandez🇲🇽 · Felipe de Jesus Rosales-Aldape🇲🇽

   The quadratic Casimir operator of the special unitary $SU(N)$ group is used to construct projection operators, which can decompose any of its reducible finite-dimensional representation spaces contained in the tensor product of two and three adjoint spaces into irreducible components. Although the method is general enough, it is specialized to the $SU(2N_f)\to SU(2)\otimes SU(N_f)$ spin-flavor symmetry group, which emerges in the baryon sector of QCD in the large-$N_c$ limit, where $N_f$ and $N_c$ are the numbers of light quark flavors and color charges, respectively. The approach leads to the construction of spin and flavor projection operators that can be implemented in the analysis of the $1/N_c$ operator expansion. The use of projection operators allows one to successfully project out the desired components of a given operator and subtract off those that are not needed. Some explicit examples in $SU(2)$ and $SU(3)$ are detailed.

   hep-phPRD(2020)·12 citations
6. 06*

   Relaxation time approximation with pair production and annihilation processes

   Samapan Bhadury🇮🇳 · Wojciech Florkowski🇵🇱 · Amaresh Jaiswal🇮🇳 · Radoslaw Ryblewski🇵🇱

   We extend the Boltzmann equation in the relaxation time approximation to explicitly include transitions between particles forming an interacting mixture. Using the detailed balance condition as well as conditions of energy-momentum and current conservation, we show that only two independent relaxation time scales are allowed in such an interacting system. Dissipative hydrodynamic equations and the form of transport coefficients is subsequently derived for this case. We find that the shear and bulk viscosity coefficients, as well as the baryon charge conductivity are independent of the transition time scale. However, the bulk viscosity and conductivity coefficients that can be attributed to the individual components of the mixture depend on the transition time.

   hep-phhep-thnucl-thPRC(2020)·18 citations
7. 07*

   Thermal radiation and inclusive production in the running coupling $k_T$ -- factorization approach

   A. V. Giannini🇧🇷 · V.P. Goncalves🇧🇷 · P.V.R.G. Silva🇧🇷

   The characteristics of the thermal radiation are investigated using a two - component model, with the hard component being described by the Color Glass Condensate formalism. The inclusive transverse momentum spectra of charged hadrons produced in proton - proton and proton - nucleus collisions at LHC energies and large - $p_T$ are estimated using the running coupling $k_T$ - factorization formula and the solution of the Balitsky - Kovchegov equation. Our results indicate that the thermal term is necessary to describe the experimental data and that the effective thermal temperature has an energy dependence similar to the saturation scale. We demonstrate that the enhancement of the thermal temperature in $pPb$ collisions is consistent with that predicted by the saturation scale.

   hep-phnucl-thEPJA(2021)·4 citations
8. 08*

   A study of $cc\bar{c}\bar{c}$ tetraquark decays in 4 muons and in $D^{(\ast )}{\bar{D}}^{(\ast )}$ at LHC

   C. Becchi · A. Giachino · L. Maiani · E. Santopinto

   We perform a quantitative analysis of the decays of $cc\bar{c}\bar{c}$ tetraquarks with $J^{PC}=0^{++},2^{++}$ into 4 muons and into hidden- and open-charm mesons and estimate, for the first time, the fully charmed tetraquark decay width. The calculated cross section upper limit is $\sim 40$ fb for the 4 muons channel, and $\sim 28$ nb for the $D^{(\ast )}{\bar{D}}^{(\ast )}\to e\mu$ channel. On the basis of our results, with the present sensitivity LHCb should detect both signals, for $0^{++}$ and $2^{++}$ fully-charmed tetraquarks.

   hep-phPLB(2020)·109 citations
9. 09*

   Modifications on parameters of $Z(4430)$ in a dense medium

   K. Azizi🇮🇷 · N. Er🇹🇷

   The charmonium-like resonance $Z_c(3900)$ and its excited state $Z(4430)$ are among the particles that are serious candidates for double heavy tetraquarks. Calculations of different parameters associated with these states both in the vacuum and the medium with finite density are of great importance. Such investigations help us clarify their nature, internal quark-gluon organization and quantum numbers. In this accordance, we extend our previous analyses on the ground state $Z_c(3900)$ to investigate the medium modifications on different parameters of the excited $Z(4430)$ state. In particular, we calculate the mass, vector self-energy and current coupling of $Z(4430)$ in terms of density, up to a density comparable to the density of the cores of massive neutron stars. The obtained results may help experimental groups aiming to study the behavior of exotic states at higher densities.

   hep-phhep-exhep-latnucl-thPLB(2020)·10 citations
10. 10*

    Novel mechanism for CMB modulation in the Standard Model

    Alexandros Karam🇪🇪 · Tommi Markkanen🇪🇪 · Luca Marzola🇪🇪 · Sami Nurmi🇫🇮 · Martti Raidal🇪🇪 · Arttu Rajantie🇬🇧

    We demonstrate that light spectator fields can source sizeable CMB anisotropies through modulated reheating even in the absence of direct couplings to the inflaton. The effect arises when the phase space of the inflaton decay is modulated by the spectator which generates masses for the decay products. We call the mechanism \textit{indirect modulation} and show that it can source perturbations even four orders of magnitude larger than the observed. Importantly, the indirect mechanism is present in the Standard Model extended with right-handed neutrinos. For a minimally coupled Higgs boson this leads to a novel lower bound on the quartic coupling and constrains the neutrino Yukawas below unity.

    hep-phastro-ph.COhep-thJHEP(2020)·11 citations
11. 11*

    CMB $V$ modes from photon-photon forward scattering revisited

    Ahmad Hoseinpour🇮🇷 · Moslem Zarei🇮🇷 · Giorgio Orlando🇮🇹 · Nicola Bartolo🇮🇹 · Sabino Matarrese🇮🇹

    Recent literature has shown that photon-photon forward scattering mediated by Euler-Heisenberg interactions may generate some amount of the circular polarization ($V$ modes) in the cosmic microwave background (CMB) photons. However, there is an apparent contradiction among the different references about the predicted level of the amplitude of this circular polarization. In this work, we will resolve this discrepancy by showing that with a quantum Boltzmann equation formalism we obtain the same amount of circular polarization as using a geometrical approach that is based on the index of refraction of the cosmological medium. We will show that the expected amplitude of $V$ modes is expected to be $\approx$ 8 orders of magnitude smaller than the amplitude of $E$-polarization modes that we actually observe in the CMB, thus confirming that it is going to be challenging to observe such a signature. Throughout the paper, we also develop a general method to study the generation of $V$ modes from photon-photon and photon-spin-1-massive-particle forward scatterings without relying on a specific interaction, which thus represent possible new signatures of physics beyond the Standard Model.

    hep-phastro-ph.COgr-qcPRD(2020)·28 citations
12. 12*

    The case of equivalence of low and high energy constraints on Regge vector spectrum in AdS/QCD

    S. S. Afonin🇷🇺 · T. D. Solomko🇷🇺

    The AdS/QCD models are believed to interpolate between low and high energy sectors of QCD. This belief is usually based on observations that many phenomenologically reasonable predictions follow from bounds imposed at high energies although the hypothetical range of applicability of semiclassical bottom-up holographic models is restricted by the gauge/gravity duality to low energies where QCD is strongly coupled. For testing the feasibility of high energy constraints it is interesting to calculate holographically some observable constants at low and high momenta independently and compare. We consider an AdS/QCD model describing the Regge-like linear spectrum of spin-1 mesons in a general form and show that under definite physical assumptions, the low-energy constraints on 2-point correlation functions lead to nearly the same numerical values for the parameters of linear radial spectrum as the high energy ones. The found approximate coincidence looks surprising in view of the fact that such a property for observables is natural for conformal theories while real strong interactions are not conformal.

    hep-phhep-thJ.Phys.G(2021)·3 citations
13. 13*

    Masses of fully heavy tetraquarks $QQ\bar{Q}\bar{Q}$ in an extended relativized quark model

    Qi-Fang Lü🇨🇳 · Dian-Yong Chen🇨🇳 · Yu-Bing Dong🇨🇳

    Inspired by recent measurement of possible fully charmed tetraquarks in LHCb Collaboration, we investigate the mass spectra of fully heavy tetraquarks $QQ\bar{Q}\bar{Q}$ in an extended relativized quark model. Our estimations indicate that the broad structure around 6.4 GeV should contain one or more ground $cc\bar{c}\bar{c}$ tetraquark states, while the narrow structure near 6.9 GeV can be categorized as the first radial excitation of $cc\bar{c}\bar{c}$ system. Moreover, with the wave functions of the tetraquarks and mesons, the strong decays of tetraquarks into heavy quarkonium pair are qualitatively discussed, which can be further checked by the LHCb and CMS Collaborations.

    hep-phhep-exnucl-thEPJC(2020)·164 citations
14. 14*

    Exploring New Physics with O(keV) Electron Recoils in Direct Detection Experiments

    Itay M. Bloch🇮🇱 · Andrea Caputo🇪🇸 · Rouven Essig🇺🇸 · Diego Redigolo🇨🇭 · Mukul Sholapurkar🇺🇸 · Tomer Volansky🇮🇱

    Motivated by the recent XENON1T results, we explore various new physics models that can be discovered through searches for electron recoils in O(keV)-threshold direct-detection experiments. First, we consider the absorption of light bosons, either as dark matter relics or being produced directly in the Sun. In the latter case, we find that keV mass bosons produced in the Sun provide an adequate fit to the data but are excluded by stellar cooling constraints. We address this tension by introducing a novel Chameleon-like axion model, which can explain the excess while evading the stellar bounds. We find that absorption of bosonic dark matter provides a viable explanation for the excess only if the dark matter is a dark photon or an axion. In the latter case, photophobic axion couplings are necessary to avoid X-ray constraints. Second, we analyze models of dark matter-electron scattering to determine which models might explain the excess. Standard scattering of dark matter with electrons is generically in conflict with data from lower-threshold experiments. Momentum-dependent interactions with a heavy mediator can fit the data with dark matter mass heavier than a GeV but are generically in tension with collider constraints. Next, we consider dark matter consisting of two (or more) states that have a small mass splitting. The exothermic (down)scattering of the heavier state to the lighter state can fit the data for keV mass splittings. Finally, we consider a subcomponent of dark matter that is accelerated by scattering off cosmic rays, finding that dark matter interacting though an O(100 keV)-mass mediator can fit the data. The cross sections required in this scenario are, however, typically challenged by complementary probes of the light mediator. Throughout our study, we implement an unbinned Monte Carlo analysis and use an improved energy reconstruction of the XENON1T events.

    hep-phhep-exJHEP(2021)·160 citations
15. 15*

    From oscillation dip to oscillation valley in atmospheric neutrino experiments

    Anil Kumar🇮🇳 · Amina Khatun🇮🇳 · Sanjib Kumar Agarwalla🇮🇳 · Amol Dighe🇮🇳

    Atmospheric neutrino experiments can show the "oscillation dip" feature in data, due to their sensitivity over a large $L/E$ range. In experiments that can distinguish between neutrinos and antineutrinos, like INO, oscillation dips can be observed in both these channels separately. We present the dip-identification algorithm employing a data-driven approach -- one that uses the asymmetry in the upward-going and downward-going events, binned in the reconstructed $L/E$ of muons -- to demonstrate the dip, which would confirm the oscillation hypothesis. We further propose, for the first time, the identification of an "oscillation valley" in the reconstructed ($E_{\mu }$,$\cos {\theta }_{\mu }$) plane, feasible for detectors like ICAL having excellent muon energy and direction resolutions. We illustrate how this two-dimensional valley would offer a clear visual representation and test of the $L/E$ dependence, the alignment of the valley quantifying the atmospheric mass-squared difference. Owing to the charge identification capability of the ICAL detector at INO, we always present our results using ${\mu }^{-}$ and ${\mu }^{+}$ events separately. Taking into account the statistical fluctuations and systematic errors, and varying oscillation parameters over their currently allowed ranges, we estimate the precision to which atmospheric neutrino oscillation parameters would be determined with the 10-year simulated data at ICAL using our procedure.

    hep-phhep-exphysics.ins-detEPJC(2021)·17 citations
16. 16*

    The thermodynamics of large-N QCD and the nature of metastable phases

    Thomas D. Cohen🇺🇸 · Scott Lawrence🇺🇸 · Yukari Yamauchi🇺🇸

    In the limit of a large number of colors (N), both Yang-Mills and quantum chromodynamics are expected to have a first-order phase transition separating a confined hadronic phase and a deconfined plasma phase. One aspect of this separation is that at large N, one can unambiguously identify a plasma regime that is strongly coupled. The existence of a first-order transition suggests that the hadronic phase can be superheated and the plasma phase supercooled. The supercooled deconfined plasma present at large N, if it exists, has the remarkable property that it has negative absolute pressure -- i.e. a pressure below that of the vacuum. For energy densities of order unity in a 1/N expansion but beyond the endpoint of the hadronic superheated phase, a description of homogeneous matter composed of ordinary hadrons with masses of order unity in a 1/N expansion can exist, and acts as though it has a temperature of $T_H$ in order unity. However, the connection between the canonical and microcanonical descriptions breaks down and the system cannot fully equilibrate as $N\to \infty$. Rather, in a hadronic description, energy is pushed to hadrons with masses that are arbitrarily large. The thermodynamic limit of large volumes becomes subtle for such systems: the energy density is no longer intensive. These conclusions follow provided that standard large N scaling rules hold, the system at large N undergoes a generic first-order phase transition between the hadronic and plasma phases and that the mesons and glueballs follow a Hagedorn-type spectrum.

    hep-phhep-thnucl-thPRC(2020)·3 citations
17. 17*

    Probing the relaxed relaxion and Higgs-portal with S1 & S2

    Ranny Budnik🇮🇱 · Hyungjin Kim🇮🇱 · Oleksii Matsedonskyi🇮🇱 · Gilad Perez🇮🇱 · Yotam Soreq🇮🇱

    We study the recent \XeT excess in context of solar scalar, specifically in the framework of Higgs-portal and the relaxion model. We show that $m_{\varphi }=1.9\text{keV}$ and $g_{\varphi e}=2.4\times 10^{-14}$ can explain the observed excess in science run 1 (SR1) analysis in the 1-7 keV range. When translated into the scalar-Higgs mixing angle, the corresponding mixing angle $\sin \theta =10^{-8}$ is intriguingly close to the maximum value of mixing angle for the technical naturalness of the scalar mass. Unlike the solar axion model, the excess favors a massive scalar field because of its softer spectrum. In the minimal scenarios we consider, the best fit parameters are in tension with stellar cooling bounds. We discuss a possibility that a large density of red giant stars may trigger a phase transition, resulting in a local scalar mass increase suppressing the stellar cooling. For the particular case of minimal relaxion scenarios, we find that such type of chameleon effects is automatically present but they can not ease the cooling bounds. They are however capable of triggering a catastrophic phase transition in the entire universe. Following this observation we derive a new set of bounds on the relaxed-relaxion parameter space.

    hep-phPRD(2021)·52 citations
18. 18*

    A novel formulation of the unintegrated gluon distribution for DIS

    Renaud Boussarie🇺🇸 · Yacine Mehtar-Tani🇺🇸

    We provide a semi-classical description of the inclusive gluon induced Deep Inelastic Scattering cross section in a way that accounts for the leading powers in both the Regge and Bjorken limits. Our approach thus allows a systematic matching of small and moderate $x_{\mathrm{Bj}}$ regimes of gluon proton structure functions. We find a new unintegrated gluon distribution with an explicit dependence on the longitudinal momentum fraction $x$ which entirely spans both the dipole operator and the gluonic Parton Distribution Function. Computing this gauge invariant gluon operator on the lattice could allow to probe the energy dependence of the saturation scale from first principles.

    hep-phnucl-thPLB(2022)·49 citations
19. 19*

    Mirror Dark Matter and Electronic Recoil Events in XENON1T

    Lei Zu🇨🇳 · Guan-Wen Yuan🇨🇳 · Lei Feng🇨🇳 · Yi-Zhong Fan🇨🇳

    Recently, the XENON1T experiment has reported the possible detection of an excess in the electronic recoil spectrum. Such an excess may indicate the presence of new physics. In this work, we suggest that the scattering of mirror electrons with ordinary electrons through photon$-$mirror photon kinetic mixing with parameter $ϵ\sim 10^{-12}(n_{{\mathrm{e}}^{\prime }}/0.2\mathrm{c}{\mathrm{m}}^{-3}{)}^{-1/2}(v_{\mathrm{c}}^0/5\times 10^9\mathrm{cm}{\mathrm{s}}^{-1}{)}^{1/2}$ may account for the excess electronic recoil events in XENON1T, where $n_{{\mathrm{e}}^{\prime }}$ is the density of mirror electron and $v_{\mathrm{c}}^0$ is the cutoff velocity of the mirror electron arriving at the earth. Interestingly, this parameter to interpret the excess of XENON1T electronic recoil spectrum are consistent with the constrains of Darkside50.

    hep-phastro-ph.HENPB(2021)·47 citations
20. 20*

    XENON1T Anomaly: A Light $Z^{\prime }$

    Manfred Lindner🇩🇪 · Yann Mambrini🇫🇷 · Tessio B. de Melo🇧🇷 · Farinaldo S. Queiroz🇧🇷

    We have witnessed the beginning of an era where dark matter and neutrino detectors can probe similar new physics phenomena. Motivated by the low-energy electron recoil spectrum observed by the dark matter experiment, XENON1T, at Gran Sasso laboratory, we interpret the observed signal not in terms of a dark matter particle, but rather in the context of a new light $Z^{\prime }$ gauge boson. We discuss how such a light $Z^{\prime }$ rises in a Two Higgs Doublet Model augmented by an abelian gauge symmetry where neutrino masses and the flavor problem are addressed, in agreement with neutrino-electron scattering data.

    hep-phastro-ph.HEhep-exhep-thPLB(2020)·71 citations
21. 21*

    One-loop running of dimension-six Higgs-neutrino operators and implications of a large neutrino dipole moment

    Mikael Chala🇪🇸 · Arsenii Titov🇮🇹

    We compute the one-loop running of the dimension-six CP-even Higgs operators in the Standard Model effective field theory involving the right-handed component of the would-be Dirac neutrinos. We discuss the implications of a large Dirac neutrino magnetic dipole moment. In particular, we demonstrate that a neutrino magnetic moment explaining the recent XENON1T excess induces Higgs and $Z$ invisible decays with branching ratios in the range $[10^{-18},10^{-12}]$. These numbers are unfortunately beyond the reach of current and near future facilities.

    hep-phJHEP(2020)·55 citations
22. 22*

    Re-examining the Solar Axion Explanation for the XENON1T Excess

    Christina Gao🇺🇸 · Jia Liu🇺🇸 · Lian-Tao Wang🇺🇸 · Xiao-Ping Wang🇺🇸 · Wei Xue🇺🇸 · Yi-Ming Zhong🇺🇸

    The XENON1T collaboration has observed an excess in electronic recoil events below $5\mathrm{keV}$ over the known background, which could originate from beyond-the-Standard-Model physics. The solar axion is a well-motivated model that has been proposed to explain the excess, though it has tension with astrophysical observations. The axions traveled from the Sun can be absorbed by the electrons in the xenon atoms via the axion-electron coupling. Meanwhile, they can also scatter with the atoms through the inverse Primakoff process via the axion-photon coupling, which emits a photon and mimics the electronic recoil signals. We found that the latter process cannot be neglected. After including the $\mathrm{keV}$ photon produced via inverse Primakoff in the detection, the tension with the astrophysical constraints can be significantly reduced. We also explore scenarios involving additional new physics to further alleviate the tension with the astrophysical bounds.

    hep-phhep-exPRL(2020)·96 citations
23. 23*

    One-loop Jet Functions by Geometric Subtraction

    Avanish Basdew-Sharma🇳🇱 · Franz Herzog🇳🇱 · Solange Schrijnder van Velzen🇳🇱 · Wouter J. Waalewijn🇳🇱

    In factorization formulae for cross sections of scattering processes, final-state jets are described by jet functions, which are a crucial ingredient in the resummation of large logarithms. We present an approach to calculate generic one-loop jet functions, by using the geometric subtraction scheme. This method leads to local counterterms generated from a slicing procedure; and whose analytic integration is particularly simple. The poles are obtained analytically, up to an integration over the azimuthal angle for the observable-dependent soft counterterm. The poles depend only on the soft limit of the observable, characterized by a power law, and the finite term is written as a numerical integral. We illustrate our method by reproducing the known expressions for the jet function for angularities, the jet shape, and jets defined through a cone or $k_T$ algorithm. As a new result, we obtain the one-loop jet function for an angularity measurement in $e^{+}{e}^{-}$ collisions, that accounts for the formally power-suppressed but potentially large effect of recoil. An implementation of our approach is made available as the GOJet Mathematica package accompanying this paper.

    hep-phJHEP(2020)·6 citations
24. 24*

    nNNPDF2.0: Quark Flavor Separation in Nuclei from LHC Data

    Rabah Abdul Khalek🇳🇱 · Jacob J. Ethier🇳🇱 · Juan Rojo🇳🇱 · Gijs van Weelden🇳🇱

    We present a model-independent determination of the nuclear parton distribution functions (nPDFs) using machine learning methods and Monte Carlo techniques based on the NNPDF framework. The neutral-current deep-inelastic nuclear structure functions used in our previous analysis, nNNPDF1.0, are complemented by inclusive and charm-tagged cross-sections from charged-current scattering. Furthermore, we include all available measurements of W and Z leptonic rapidity distributions in proton-lead collisions from ATLAS and CMS at $\sqrt{s}=5.02$ TeV and 8.16 TeV. The resulting nPDF determination, nNNPDF2.0, achieves a good description of all datasets. In addition to quantifying the nuclear modifications affecting individual quarks and antiquarks, we examine the implications for strangeness, assess the role that the momentum and valence sum rules play in nPDF extractions, and present predictions for representative phenomenological applications. Our results, made available via the LHAPDF library, highlight the potential of high-energy collider measurements to probe nuclear dynamics in a robust manner.

    hep-phhep-exnucl-exnucl-thJHEP(2020)·122 citations
25. 25*

    Higgs, top and electro-weak precision measurements at future $e^{+}{e}^{-}$ colliders; a combined effective field theory analysis with renormalization mixing

    Sunghoon Jung🇰🇷 · Junghwan Lee🇰🇷 · Martin Perelló🇪🇸 · Junping Tian🇯🇵 · Marcel Vos🇪🇸

    This paper presents a combined analysis of the potential of a future electron-positron collider to constrain the Higgs, top and electro-weak (EW) sectors of the Standard Model Effective Field Theory (SMEFT). The leading contributions of operators involving top quarks arise mostly at one-loop suppressed order and can be captured by the renormalization group mixing with Higgs operators. We perform global fits with an extended basis of 29 parameters, including both Higgs and top operators, to the projections for the Higgs, top and electro-weak precision measurements at the International Linear Collider (ILC). The determination of the Higgs boson couplings in the 250 GeV stage of the ILC is initially severely degraded by the additional top-quark degrees of freedom, but can be nearly completely recovered by the inclusion of precise measurements of top-quark EW couplings at the LHC. The physical Higgs couplings are relatively robust, as the top mass is larger than the energy scale of EW processes. The effect of the top operators on the bounds on the Wilson coefficients is much more pronounced and may limit our ability to identify the source of deviations from the Standard Model. Robust global bounds on all Wilson coefficients are only obtained when the 500 GeV stage of the ILC is included.

    hep-phhep-exPRD(2022)·21 citations
26. 26*

    Automated evaluation of electroweak Sudakov logarithms in Sherpa

    Enrico Bothmann🇩🇪 · Davide Napoletano🇮🇹

    We present an automated implementation for the calculation of one-loop double and single Sudakov logarithms stemming from electroweak radiative corrections within the Sherpa event generation framework, based on the derivation in[1]. At high energies, these logarithms constitute the leading contributions to the full NLO electroweak corrections. As examples, we show applications for relevant processes at both the LHC and future hadron colliders, namely on-shell W boson pair production, EW-induced dijet production and electron-positron production in association with four jets, providing the first estimate of EW corrections at this multiplicity.

    hep-phhep-exEPJC(2020)·42 citations
27. 27*

    Photon Collider for energies 1-2 TeV

    Ilya F. Ginzburg🇷🇺 · Gleb L. Kotkin🇷🇺

    We discuss a photon collider based on the $e^{+}{e}^{-}$ \ linear collider with energies of $2E=1÷2$ TeV in cms (ILC, CLIC, ...). Previously, this energy range was considered hopeless for the experiment in the foreseeable future. We discuss the realization of the TeV PLC based on modern lasers. A small modification of the laser-optical system prepared for the photon collider with energy of $E\approx 250$ GeV will be sufficient if the parameters are chosen optimally. The high-energy part of the photon spectrum does not depend on design details and is well separated from the low-energy part. That is a narrow band near the upper boundary, about 5\% wide. The high-energy integrated \ggam luminosity is about 1/5 and the maximum differential luminosity is about 1/4 of the corresponding values for the photon collider with $E\approx 250$ GeV.

    hep-phhep-exPhys.Part.Nucl.(2021)·7 citations
28. 28*

    QED Plasma at Extremely High Temperature and Density

    Samina Masood🇺🇸

    We use the renormalization scheme of QED (Quantum Electrodynamics) in real-time formalism to calculate the effective parameters of the theory, indicating the existence of relativistic QED plasma at extremely high temperatures and extremely high densities. High-density plasma is found inside the stellar cores and high temperature QED plasma could only exist, right after the neutrino decoupling temperature in the early universe, before the nucleosynthesis is complete. Radiation couples with the medium through the vacuum polarization in a hot and dense medium. Calculating the vacuum polarization tensor in a medium, the effect of radiation on matter is investigated in such a medium. We explicitly compute the parameters of QED plasma such as plasma frequency, Debye shielding length and the propagation frequency in terms of temperature and density of the superhot and superdense medium, respectively. This study helps to understand short term existence of QED plasma in the superhot and superdense systems.

    hep-ph1 citation
29. 29*

    $I=1/2$ $S$-wave and $P$-wave $K\pi$ scattering and the $\kappa$ and $K^{\ast }$ resonances from lattice QCD

    Gumaro Rendon🇺🇸 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · John Negele🇺🇸 · Srijit Paul🇩🇪 · Marcus Petschlies🇩🇪 · Andrew Pochinsky🇺🇸 · Giorgio Silvi🇩🇪 · Sergey Syritsyn🇺🇸

    We present a lattice-QCD determination of the elastic isospin-$1/2$ $S$-wave and $P$-wave $K\pi$ scattering amplitudes as a function of the center-of-mass energy using Lüscher's method. We perform global fits of $K$-matrix parametrizations to the finite-volume energy spectra for all irreducible representations with total momenta up to $\sqrt{3}\frac{2\pi }{L}$; this includes irreps that mix the $S$- and $P$-waves. Several different parametrizations for the energy dependence of the $K$-matrix are considered. We also determine the positions of the nearest poles in the scattering amplitudes, which correspond to the broad $\kappa$ resonance in the $S$-wave and the narrow $K^{\ast }(892)$ resonance in the $P$-wave. Our calculations are performed with $2+1$ dynamical clover fermions for two different pion masses of $317.2(2.2)$ and $175.9(1.8)$ MeV. Our preferred $S$-wave parametrization is based on a conformal map and includes an Adler zero; for the $P$-wave we use a standard pole parametrization including Blatt-Weisskopf barrier factors. The $S$-wave $\kappa$-resonance pole positions are found to be $\left[0.86(12)-0.309(50)i\right]\mathrm{GeV}$ at the heavier pion mass and $\left[0.499(55)-0.379(66)i\right]\mathrm{GeV}$ at the lighter pion mass. The $P$-wave $K^{\ast }$-resonance pole positions are found to be $\left[0.8951(64)-0.00250(21)i\right]\mathrm{GeV}$ at the heavier pion mass and $\left[0.8718(82)-0.0130(11)i\right]\mathrm{GeV}$ at the lighter pion mass, which corresponds to couplings of $g_{K^{\ast }K\pi }=5.02(26)$ and $g_{K^{\ast }K\pi }=4.99(22)$, respectively.

    ↳ hep-lathep-phPRD(2020)·44 citations
30. 30*

    Scalar scattering amplitude in Gaussian wave-packet formalism

    Kenzo Ishikawa🇯🇵 · Kenji Nishiwaki🇮🇳 · Kin-ya Oda🇯🇵

    We compute an $s$-channel $2\to 2$ scalar scattering $\varphi \varphi \to \Phi \to \varphi \varphi$ in the Gaussian wave-packet formalism at the tree-level. We find that wave-packet effects, including shifts of the pole and width of the propagator of $\Phi$, persist even when we do not take into account the time-boundary effect for $2\to 2$, proposed earlier. The result can be interpreted that a heavy scalar $1\to 2$ decay $\Phi \to \varphi \varphi$, taking into account the production of $\Phi$, does not exhibit the in-state time-boundary effect unless we further take into account in-boundary effects for the $2\to 2$ scattering. We also show various plane-wave limits.

    ↳ hep-thhep-phquant-phPTEP(2020)·11 citations
31. 31*

    What's in the core of massive neutron stars?

    Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷

    When hadron-quark continuity is formulated in terms of a topology change at a density higher than twice the nuclear matter densiy $n_0$ the core of massive compact stars can be described in terms of quasiparticles of fractional baryon charges, behaving neither like pure baryons nor deconfined quarks. Hidden symmetries, both local gauge and pseudo-conformal (or broken scale), emerge and give rise to the long-standing quenched $g_A$ in nuclear Gamow-Teller transitions at $\sim n_0$ and to the pseudo-conformal sound velocity $v_{pcs}^2/c^2\approx 1/3$ at $\text{gsim}3n_0$. These properties are confronted with the recent observations in superallowed Gamow-Teller transitions and in astrophysical observations.

    ↳ nucl-thastro-ph.HEhep-ph17 citations
32. 32*

    A lattice investigation of exotic tetraquark channels

    R. J. Hudspith🇩🇪 · B. Colquhoun🇨🇦 · A. Francis🇨🇭 · R. Lewis🇨🇦 · K. Maltman🇨🇦

    We perform an $n_f=2+1$ lattice study of a number of channels where past claims exist in the literature for the existence of strong-interaction-stable light-heavy tetraquarks. We find no evidence for any such deeply-bound states, beyond the $J^P=1^{+}$, $I=0$ $ud\bar{b}\bar{b}$ and $I=1/2$ $ls\bar{b}\bar{b}$ states already identified in earlier lattice studies. We also describe a number of systematic improvements to our previous lattice studies, including working with larger $m_{\pi }L$ to better suppress possible finite volume effects, employing extended sinks to better control excited-state contamination, and expanding the number of operators used in the GEVP analyses. Our results also allow us to rule out several phenomenological models which predict significant tetraquark binding in channels where no such binding is found.

    ↳ hep-lathep-phPRD(2020)·99 citations
33. 33*

    Global polarization in heavy-ion collisions based on axial vortical effect

    Yu. B. Ivanov🇷🇺

    Global polarization of $\Lambda$ and $\bar{\Lambda }$ is calculated based on the axial vortical effect (AVE). Simulations are performed within the model of the three-fluid dynamics. Equations of state with the deconfinement transition result in a good agreement with STAR data for both $\Lambda$ and $\bar{\Lambda }$ polarization, in particular, with the $\Lambda$-$\bar{\Lambda }$ splitting. Suppression of the gravitational-anomaly contribution required for the data reproduction is in agreement with predictions of the QCD lattice simulations. Predictions for the global polarization in forthcoming experiments at lower collision energies are made. These forthcoming data will provide a critical test for the AVE and thermodynamic mechanisms of the polarization.

    ↳ nucl-thhep-phPRC(2020)·20 citations
34. 34*

    Model-Independent Perspectives on Coupled Dark Energy and the Swampland

    Tao Yang🇰🇷

    We present a general model-independent approach to study the coupled dark energy and the string Swampland criteria. We show how the dark sector interaction is degenerated with the equation of state of dark energy in the context of the expansion of the Universe. With priors for either of them, the dynamics of dark energy and the dark sector interactions can be reconstructed together with the bounds of the Swampland criteria. Combining cosmic chronometers, baryon acoustic oscillation (BAO), and Type Ia supernovae our results suggest a mild $1\sigma$ significance of dark sector interactions at low redshift for the coupled quintessence. The Lyman-$\alpha$ BAO at $z=2.34$ leads a $2\sigma$ signal of nonzero interactions at high redshift. The implications for coupled quintessence are discussed.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2020)·14 citations
35. 35*

    Stochastic inflationary dynamics beyond slow-roll and consequences for primordial black hole formation

    Guillermo Ballesteros🇪🇸 · Julián Rey🇪🇸 · Marco Taoso🇮🇹 · Alfredo Urbano🇮🇹

    We consider the impact of quantum diffusion on inflationary dynamics during an ultra-slow-roll phase, which can be of particular significance for the formation of primordial black holes. We show, by means of a fully analytical approach, that the power spectrum of comoving curvature perturbations computed in stochastic inflation matches precisely, at the linear level, the result obtained by solving the Mukhanov-Sasaki equation, even in the presence of an ultra-slow-roll phase. We confirm this result numerically in a model in which the inflaton has a polynomial potential and is coupled quadratically to the Ricci scalar. En route, we assess the role that quantum noise plays in the presence of an ultra-slow-roll phase, and clarify the issue of the quantum-to-classical transition in this scenario.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2020)·71 citations
36. 36*

    How does a dark compact object ringdown?

    Elisa Maggio🇮🇹 · Luca Buoninfante🇯🇵 · Anupam Mazumdar🇳🇱 · Paolo Pani🇮🇹

    A generic feature of nearly out-of-equilibrium dissipative systems is that they resonate through a set of quasinormal modes. Black holes - the absorbing objects par excellence - are no exception. When formed in a merger, black holes vibrate in a process called "ringdown", which leaves the gravitational-wave footprint of the event horizon. In some models of quantum gravity which attempt to solve the information-loss paradox and the singularities of General Relativity, black holes are replaced by regular, horizonless objects with a tiny effective reflectivity. Motivated by these scenarios, here we develop a generic framework to the study of the ringdown of a compact object with various shades of darkness. By extending the black-hole membrane paradigm, we map the interior of any compact object in terms of the bulk and shear viscosities of a fictitious fluid located at the surface, with the black-hole limit being a single point in a three-dimensional parameter space. We unveil some remarkable features of the ringdown and some universal properties of the light ring in this framework. We also identify the region of the parameter space which can be probed by current and future gravitational-wave detectors. A general feature is the appearance of mode doublets which are degenerate only in the black-hole limit. We argue that the merger event GW150914 already imposes a strong lower bound on the compactness of the merger remnant of approximately 99% of the black-hole compactness. This places model-independent constraints on black-hole alternatives such as diffuse "fuzzballs" and nonlocal stars.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2020)·116 citations
37. 37*

    Hadronic vs leptonic models for $\gamma$-ray emission from VER J2227+608

    Siming Liu🇨🇳 · Houdun Zeng🇨🇳 · Yuliang Xin🇨🇳 · Hui Zhu🇨🇳

    Recent observations of VER J2227+608 reveal a broken power $\gamma$-ray spectrum with the spectral index increasing from $\sim 1.8$ in the GeV energy range to $\sim 2.3$ in the TeV range. Such a spectral break can be attributed to radiative energy loss of energetic electrons in the leptonic scenario for the $\gamma$-ray emission, which, in combination with characteristic age of the nearby pulsar, can be used to constrain magnetic field in the emission region. We show that the radio and X-ray observations can also be explained in such a scenario. In the hadronic scenario, the spectral break can be attributed to diffusion of energetic ions in a turbulent medium and detailed spectral measurement can be used to constrain the diffusion coefficient. These two models, however, predict drastically different spectra above 100 TeV, which will be uncovered with future high-resolution observations, such as LHAASO and/or CTA.

    ↳ astro-ph.HEhep-phApJL(2020)·35 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.