Wed·Nov 13, 2019Wednesday·November 13, 2019

1. 01*

   Extracting many-body correlators of saturated gluons with precision from inclusive photon+dijet final states in deeply inelastic scattering

   Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸

   We highlight the principal results of a computation in the Color Glass Condensate effective field theory (CGC EFT) of the next-to-leading order (NLO) impact factor for inclusive photon+dijet production at Bjorken $x_{\mathrm{Bj}}\ll 1$ in deeply inelastic electron-nucleus (e+A DIS) collisions. When combined with extant results for next-to-leading log $x_{\mathrm{Bj}}$ JIMWLK renormalization group (RG) evolution of gauge invariant two-point ("dipole") and four-point ("quadrupole") correlators of light-like Wilson lines, the inclusive photon+dijet e+A DIS cross-section can be determined to $\sim 10$\% accuracy. Our computation simultaneously provides the ingredients to compute fully inclusive DIS, inclusive photon, inclusive dijet and inclusive photon+jet channels to the same accuracy. This makes feasible quantitative extraction of many-body correlators of saturated gluons and precise determination of the saturation scale $Q_{S,A}(x_{\mathrm{Bj}})$ at a future Electron-Ion Collider. An interesting feature of our NLO result is the structure of the violation of the soft gluon theorem in the Regge limit. Another is the appearance in gluon emission of time-like non-global logs which also satisfy JIMWLK RG evolution.

   hep-phhep-thnucl-thPRD(2020)·33 citations
2. 02*

   NLO impact factor for inclusive photon$+$dijet production in $e+A$ DIS at small $x$

   Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸

   We compute the next-to-leading order (NLO) impact factor for inclusive photon $+$dijet production in electron-nucleus (e+A) deeply inelastic scattering (DIS) at small $x$. An important ingredient in our computation is the simple structure of ``shock wave" fermion and gluon propagators. This allows one to employ standard momentum space Feynman diagram techniques for higher order computations in the Regge limit of fixed $Q^2\gg {\Lambda }_{\mathrm{QCD}}^2$ and $x\to 0$. Our computations in the Color Glass Condensate (CGC) effective field theory include the resummation of all-twist power corrections $Q_s^2/Q^2$, where $Q_s$ is the saturation scale in the nucleus. We discuss the structure of ultraviolet, collinear and soft divergences in the CGC, and extract the leading logs in $x$; the structure of the corresponding rapidity divergences gives a nontrivial first principles derivation of the JIMWLK renormalization group evolution equation for multiparton lightlike Wilson line correlators. Explicit expressions are given for the $x$-independent $O({\alpha }_s)$ contributions that constitute the NLO impact factor. These results, combined with extant results on NLO JIMWLK evolution, provide the ingredients to compute the inclusive photon $+$ dijet cross-section at small $x$ to $O({\alpha }_s^3\ln (x))$. First results for the NLO impact factor in inclusive dijet production are recovered in the soft photon limit. A byproduct of our computation is the LO photon+ 3 jet (quark-antiquark-gluon) cross-section.

   hep-phhep-thnucl-thPRD(2020)·87 citations
3. 03*

   A Twist on Broken U(3)xU(3) Supersymmetry

   Scott Chapman🇺🇸

   What symmetry breaking would be required for gauginos from a supersymmetric theory to behave like left-handed quarks of the Standard Model? Starting with a supersymmetric SU(3)xSU(3)xU(1)xU(1) gauge theory, the 18 adjoint-representation gauginos are replaced with 2 families of 9 gauginos in the (3,3*) representation of the group. After this explicit breaking of supersymmetry, two-loop quadratic divergences still cancel at a unification scale. Coupling constant unification is supported by deriving the theory from an SU(3)xSU(3)xSU(3)xSU(3) Grand Unified Theory (GUT). Sin^2 of the Weinberg angle for the GUT is 1/4 rather than 3/8, leading to a lower unification scale than usually contemplated, ~10^9 GeV. After spontaneous gauge symmetry breaking to SU(3)xSU(2)xU(1), the theory reproduces the main features of the Standard Model for two families of quarks and leptons, with gauginos playing the role of left-handed quarks and sleptons playing the role of the Higgs boson. An extension to the theory is sketched that incorporates the third family of quarks and leptons.

   hep-phhep-thQuantum Stud.: Math. Found., 8(1), 121 (2…·0 citations
4. 04*

   Explanation for why the Early Universe was Stable and Dominated by the Standard Model

   Mark P. Hertzberg🇺🇸 · Mudit Jain🇺🇸

   The Standard Model (SM) possesses an instability at high scales that would be catastrophic during or just after inflation, and yet no new physics has been seen to alter this. Furthermore, modern developments in quantum gravity suggest that the SM degrees of freedom are not unique; that a typical low energy effective theory should include a large assortment of hidden sector degrees of freedom. It is therefore puzzling that cosmological constraints from BBN and CMB reveal that the early universe was almost entirely dominated by the SM, when the inflaton $\varphi$ could have decayed into many sectors. In this work we propose the following explanation for all of this: we allow the lowest dimension operators with natural coefficients between the inflaton and both the Higgs and hidden sectors. Such hidden sectors are assumed to be entirely natural; this means all unprotected masses are pushed up to high scales and project out of the spectrum, while only massless (or protected) degrees of freedom remain, and so the inflaton can only reheat these sectors through higher dimension (and suppressed) operators. On the other hand, the SM possesses a special feature: it includes a light Higgs $H$, presumably for life to exist, and hence it allows a super-renormalizable coupling to the inflaton $\varphi H^{†}H$, which allows rapid decay into the SM. We show that this naturally (i) removes the instability in the Higgs potential both during and after inflation due to a tree-level effect that increases the value of the Higgs self-coupling from the IR to the UV when one passes the inflaton mass, (ii) explains why the SM is dominant in the early universe, (iii) allows dark matter to form in hidden sector/s through subsequent dynamics (or axions, etc), (iv) allows for high reheating and baryogenesis, and (v) accounts for why there so far has been no direct detection of dark matter or new physics beyond the SM.

   hep-phastro-ph.COgr-qchep-thJCAP(2020)·9 citations
5. 05*

   Pion Beta Decay and CKM Unitarity

   Andrzej Czarnecki🇨🇦 · William J. Marciano🇺🇸 · Alberto Sirlin🇺🇸

   Pion beta decay, ${\pi }^{+}\to {\pi }^0{e}^{+}\nu (\gamma )$, provides a theoretically clean $\pm 0.3\%$ determination of the CKM matrix element $V_{\text{ud}}$. That value falls short of super-allowed nuclear beta decays where an order of magnitude better precision already exists. We advocate a new strategy for utilizing pion beta decay, based on its role in determining $V_{\text{us}}/V_{\text{ud}}$ via the ratio $R_V=\Gamma \left(K\to \pi l\nu (\gamma )\right)/\Gamma \left({\pi }^{+}\to {\pi }^0{e}^{+}\nu (\gamma )\right)$. $R_V$ measures $f_{+}^K(0)|V_{\text{us}}|/f_{+}^{\pi }(0)|V_{\text{ud}}|$ and is insensitive to the Fermi constant and some radiative corrections. Its dependence on the ratio of form factors may also prove useful for lattice gauge theory calculations. Employing a lattice based value $f_{+}^K(0)/f_{+}^{\pi }(0)=0.970(2)$, we find $V_{\text{us}}/V_{\text{ud}}=0.22918(88)$ compared to $V_{\text{us}}/V_{\text{ud}}=0.23131(45)$ obtained from $R_A=\Gamma (K\to \mu \nu (\gamma ))/\Gamma (\pi \to \mu \nu (\gamma ))$. Those vector and axial-vector based $V_{\text{us}}/V_{\text{ud}}$ values exhibit a 2.2$\sigma$ discrepancy. That tension may be relieved by a shift in the lattice $f_{+}^K(0)/f_{+}^{\pi }(0)$ towards the consistency range 0.961(4), changes in experimental input or new physics. Other implications of $R_V$ and $R_A$ are also discussed.

   hep-phhep-exhep-latnucl-thPRD(2020)·55 citations
6. 06*

   Connecting Light Dirac Neutrinos to a Multi-component Dark Matter Scenario in Gauged $B-L$ Model

   Dibyendu Nanda🇮🇳 · Debasish Borah🇮🇳

   We propose a new gauged $B-L$ extension of the standard model where light neutrinos are of Dirac type, naturally acquiring sub-eV mass after electroweak symmetry breaking, without any additional global symmetries. This is realised by choosing a different $B-L$ charge for right handed neutrinos than the usual $-1$ so that the Dirac Yukawa coupling involves an additional neutrinophilic scalar doublet instead of the usual Higgs doublet. The model can be made anomaly free by considering four additional chiral fermions which give rise to two massive Dirac fermions by appropriate choice of singlet scalars. The choice of scalars not only helps in achieving the desired particle mass spectra via spontaneous symmetry breaking, but also leaves a remnant $Z_2\times Z_2^{\prime }$ symmetry to stabilise the two dark matter candidates. Apart from this interesting link between Dirac nature of light neutrinos and multi-component dark matter sector, we also find that the dark matter parameter space is constrained mostly by the cosmological upper limit on effective relativistic degrees of freedom $\Delta N_{\mathrm{eff}}$ which gets enhanced in this model due to the thermalisation of the light right handed neutrinos by virtue of their sizeable $B-L$ gauge interactions.

   hep-phastro-ph.COEPJC(2020)·54 citations
7. 07*

   Testing strong-field QED close to the fully non-perturbative regime using aligned crystals

   A. Di Piazza🇩🇪 · T. N. Wistisen🇩🇰 · M. Tamburini🇩🇪 · U. I. Uggerh\{o}j🇩🇰

   Processes occurring in the strong-field regime of QED are characterized by background electromagnetic fields of the order of the critical field $F_{cr}=m^2{c}^3/\hslash |e|$ in the rest frame of participating charges. It has been conjectured that if in their rest frame electrons/positrons experience field strengths of the order of $F_{cr}/{\alpha }^{3/2}\approx 1600F_{cr}$, with $\alpha \approx 1/137$ being the fine-structure constant, their effective coupling with radiation becomes of the order of unity. Here we show that channeling radiation by ultrarelativistic electrons with energies of the order of a few TeV on thin tungsten crystals allows to test the predictions of QED close to this fully non-perturbative regime by measuring the angularly resolved single photon intensity spectrum. The proposed setup features the unique characteristics that essentially all electrons 1) undergo at most a single photon emission and 2) experience at the moment of emission and in the angular region of interest the maximum allowed value of the field strength, which at $2\text{TeV}$ exceeds $F_{cr}$ by more than two orders of magnitudes in their rest frame.

   hep-phPRL(2020)·36 citations
8. 08*

   Unitarity in Multi-Higgs Production

   A. Curko🇭🇺 · G. Cynolter🇭🇺

   It has long been known that perturbative calculations in scalar multi-particle production could break down since fast growing amplitudes appear. A recent calculation in the regime $\lambda n\gg 1$, where $n$ is the multiplicity and $\lambda$ is the self-coupling, gives an amplitude which grows exponentially with the energy, resulting in a divergent propagator and leading to the violation of perturbative unitarity. In this paper the transition rate is calculated from the solution of the self-consistent Schwinger-Dyson equation in spectral representation. We get an amplitude growing quadratically with the energy which leads to an asymptotically decreasing propagator contrary to previous results. Hence, unitarity is not violated, as expected in the Standard Model.

   hep-ph2 citations
9. 09*

   Exclusive Meson Photo- and Electro-production, a Window on the Structure of Hadronic Matter

   J.M. Laget🇺🇸

   At high energy, exclusive meson photo- and electro-production give access to the structure of hadronic matter. At low momentum transfers, the exchange of a few Regge trajectories leads to a comprehensive account of the cross-sections. Among these trajectories, which are related to the mass spectrum of families of mesons, the Pomeron plays an interesting role as it is related to glue-ball excitations. At high momentum transfers, the exchange of these collective excitations is expected to reduce to the exchange of their simplest (quark or gluon) components. However, contributions from unitarity rescattering cuts are relevant even at high energies. In the JLab energy range, the asymptotic regime, where the players in the game are current quarks and massless gluons has not been reached yet. One has to rely on more effective degrees of freedom adapted to the scale of the probe. A consistent picture, the Partonic Non-Perturbative Regime, is emerging. The properties of its various components (dressed propagators, effective coupling constants, quark wave functions, shape of the Regge trajectories, etc) provide us with various links to hadron properties. I will review the status of the field, will put in perspective the current achievements at JLab, SLAC and Hermes, and will assess future developments that are made possible by continuous electron beams at higher energies.

   hep-phPPNP(2020)·20 citations
10. 10*

    Systematics of chemical freeze-out parameters in heavy-ion collision experiments

    Sumana Bhattacharyya🇮🇳 · Deeptak Biswas🇮🇳 · Sanjay K. Ghosh🇮🇳 · Rajarshi Ray🇮🇳 · Pracheta Singha🇮🇳

    We discuss systematic uncertainties in the chemical freeze-out parameters from the ${\chi }^2$ analysis of hadron multiplicity ratios in the heavy-ion collision experiments. The systematics due to the choice of specific hadron ratios are found to lie within the experimental uncertainties. The variations obtained by removing the usual constraints on the conserved charges show similar behavior. The net charge to net baryon ratios in such unconstrained systems are commensurate with the expected value obtained from the protons and neutrons of the colliding nuclei up to the center of mass energies $\sim 40$ GeV. Beyond that the uncertainties in this ratio gradually increases, possibly indicating the reduction in baryon stopping.

    hep-phnucl-thPRD(2020)·32 citations
11. 11*

    Energy density at kinetic freeze-out in Pb-Pb collisions at the LHC using the Tsallis distribution

    M. D. Azmi🇮🇳 · T. Bhattacharyya🇷🇺 · J. Cleymans🇿🇦 · M. Paradza🇿🇦

    The thermodynamic parameters like energy density, pressure, entropy density, temperature and particle density are determined from the transverse momentum distributions of charged particles in Pb-Pb collisions at the LHC. The results show a clear increase with the centrality and the beam energy in all parameters. It is determined that in the final freeze-out stage the energy density reaches a value of about 0.039 GeV/fm${}^3$ for the most central collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. This is less than that at chemical freeze-out where the energy density is about 0.36 GeV/fm${}^3$. This decrease approximately follows a $T^4$ law. The results for the pressure and entropy density are also presented for each centrality class at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV.

    hep-phnucl-thJ.Phys.G(2020)·23 citations
12. 12*

    Neutrino mass and dark matter from an approximate $B-L$ symmetry

    Duong Van Loi🇻🇳 · Phung Van Dong🇻🇳 · Dang Van Soa🇺🇸

    We argue that neutrino mass and dark matter can arise from an approximate $B-L$ symmetry. This idea can be realized in a minimal setup of the flipped 3-3-1 model, which discriminates lepton families while keeping universal quark families and uses only two scalar triplets in order for symmetry breaking and mass generation. This proposal contains naturally an approximate non-Abelian $B-L$ symmetry which consequently leads to an approximate matter parity. The approximate symmetries produce small neutrino masses in terms of type II and III seesaws and may make dark matter long lived. Additionally, dark matter candidate is either unified with the Higgs doublet by gauge symmetry or acted as an inert multiplet. The Peccei-Quinn symmetry is discussed. The gauge and scalar sectors are exactly diagonalized. The signals of the new physics at colliders are examined.

    hep-phhep-thJHEP(2020)·11 citations
13. 13*

    Probing flavoured Axions in the Tail of $B_q\to {\mu }^{+}{\mu }^{-}$

    Johannes Albrecht🇩🇪 · Emmanuel Stamou🇺🇸 · Robert Ziegler🇨🇭 · Roman Zwicky🇬🇧

    We discuss how LHC di-muon data collected to study $B_q\to \mu \mu$ can be used to constrain light particles with flavour-violating couplings to $b$-quarks. Focussing on the case of a flavoured QCD axion, $a$, we compute the decay rates for $B_q\to \mu \mu a$ and the SM background process $B_q\to \mu \mu \gamma$ near the kinematic endpoint. These rates depend on non-perturbative $B_q\to {\gamma }^{(\ast )}$ form factors with on- or off-shell photons. The off-shell form factors -- relevant for generic searches for beyond-the-SM particles -- are discussed in full generality and computed with QCD sum rules for the first time. With these results, we analyse available LHCb data to obtain the sensitivity on $B_q\to \mu \mu a$ at present and future runs. We find that the full LHCb dataset alone will allow to probe axion-coupling scales of the order of $10^6$ GeV for both $b\to d$ and $b\to s$ transitions.

    hep-phJHEP(2020)·36 citations
14. 14*

    Probing muonic charged current nonstandard interactions at decay-at-rest facilities in conjunction with T2HK

    Soumya C.🇮🇳 · Monojit Ghosh🇸🇪 · Sushant K. Raut🇰🇷 · Nita Sinha🇮🇳 · Poonam Mehta🇮🇳

    The muon decay-at-rest ($\mu$-DAR) facility provides us with an ideal platform to probe purely muonic charged-current nonstandard neutrino interactions (NSIs). We propose to probe this class of NSI effects using antineutrinos from a $\mu$-DAR source in conjunction with neutrinos from the future Tokai to Kamioka superbeam experiment with megaton Hyper Kamiokande detector (T2HK). Even though muonic NSIs are absent in neutrino production at T2HK, we show that our proposed hybrid setup comprising $\mu$-DAR and T2HK helps in alleviating the parameter degeneracies that can arise in data. Analytic considerations reveal that the oscillation probability is most sensitive to the NSI parameter in the $\mu$-e sector. For this parameter, we show that the $\mu$-DAR setup can improve on the existing bounds down to around 0.01, especially when the data are combined with neutrino data from T2HK experiment due to the lifting of parameter degeneracies. The high precision with which $\mu$-DAR can measure ${\delta }_{\mathrm{CP}}$ is shown to be robust even in the presence of the considered NSIs. Finally, we show that the combination of $\mu$-DAR along with T2HK can also be used to put mild constraints on the NSI phase in the vicinity of the maximal CP-violating value for the chosen benchmark value of ${\epsilon }_{\mu e}^{\mu e}=0.01$.

    hep-phPRD(2020)·14 citations
15. 15*

    Revisiting the $O({\alpha }^2)$ Initial State QED Corrections to $e^{+}{e}^{-}$ Annihilation into a Neutral Boson

    J. Blümlein🇩🇪 · A. De Freitas🇩🇪 · C.G. Raab🇦🇹 · K. Schönwald🇩🇪

    At $e^{+}{e}^{-}$ colliders the QED--initial state radiation forms a large part of the radiative corrections. Their precise and fast evaluation is an essential asset for the experiments at LEP, the ILC and the FCC-ee, operating at high luminosity. A long standing problem in the analytic calculation of the $O({\alpha }^2)$ initial state corrections concerns a discrepancy which has been observed between the result of Berends et al. (1988) \cite{Berends:1987ab} in the limit $m_e^2\ll s$ and the result by Blümlein et al. (2011) \cite{Blumlein:2011mi} using massive operator matrix elements deriving this limit directly. In order to resolve this important issue we recalculated this process by integrating directly over the phase space without any approximation. For parts of the corrections we find exact solutions of the cross section in terms of iterated integrals over square root valued letters representing incomplete elliptic integrals and iterations over them. The expansion in the limit $m_e^2\ll s$ reveals errors in the constant $O({\alpha }^2)$ term of the former calculation and yields agreement with the calculation based on massive operator matrix elements, which has impact on the experimental analysis programs. This finding also explicitly proofs the factorization of massive initial state particles in the high energy limit including the terms of $O({\alpha }^2)$ for this process.

    hep-phhep-exPoS(2019)·0 citations
16. 16*

    Dilaton portal in strongly interacting twin Higgs models

    Aqeel Ahmed🇧🇪 · Barry M. Dillon🇸🇮 · Saereh Najjari🇧🇪

    We consider a strongly interacting twin Higgs (SITH) model where an ultraviolet completion of twin Higgs mechanism is realized by a strongly coupled approximately scale invariant theory. Besides the Standard Model (SM) and twin sectors, the low energy effective theory contains a relatively light scalar called a dilaton --- the pseudo Goldstone boson of spontaneously broken scale invariance. The dilaton provides a unique portal between the SM and twin sectors whose phenomenology could provide an important probe of the twin Higgs mechanism. As a concrete example, we consider a holographic twin Higgs model where the role of the dilaton is played by the radion. The phenomenology of this model is fully determined by a few parameters and our analysis concludes that at the HL-LHC (14 TeV) and HE-LHC (27 TeV) with 3000/fb most of the natural parameter space can be probed.

    hep-phhep-thJHEP(2020)·8 citations
17. 17*

    The Cosmological Evolution of Light Dark Photon Dark Matter

    Samuel D. McDermott🇺🇸 · Samuel J. Witte🇪🇸

    Light dark photons are subject to various plasma effects, such as Debye screening and resonant oscillations, which can lead to a more complex cosmological evolution than is experienced by conventional cold dark matter candidates. Maintaining a consistent history of dark photon dark matter requires ensuring that the super-thermal abundance present in the early Universe $\text{(i)}$ does not deviate significantly after the formation of the CMB, and $\text{(ii)}$ does not excessively leak into the Standard Model plasma after BBN. We point out that the role of non-resonant absorption, which has previously been neglected in cosmological studies of this dark matter candidate, produces strong constraints on dark photon dark matter with mass as low as $10^{-22}$ eV. Furthermore, we show that resonant conversion of dark photons after recombination can produce excessive heating of the IGM which is capable of prematurely reionizing hydrogen and helium, leaving a distinct imprint on both the Ly$-\alpha$ forest and the integrated optical depth of the CMB. Our constraints surpass existing cosmological bounds by more than five orders of magnitude across a wide range of dark photon masses.

    hep-phastro-ph.COPRD(2020)·144 citations
18. 18*

    Prospects of Measuring Oscillated Decay-at-Rest Neutrinos at Long Baselines

    Roni Harnik🇺🇸 · Kevin J. Kelly🇺🇸 · Pedro A.N. Machado🇺🇸

    In addition to the next generation of beam-based neutrino experiments and their associated detectors, a number of intense, low-energy neutrino production sources from decays at rest will be in operation. In this work, we explore the physics opportunities with decay-at-rest neutrinos for complementary measurements of oscillation parameters at long baselines. The J-PARC Spallation Neutron Source, for example, will generate neutrinos from a variety of decay-at-rest (DAR) processes, specifically those of pions, muons, and kaons. Other proposed sources will produce large numbers of stopped pions and muons. We demonstrate the ability of the upcoming Hyper-Kamiokande experiment to detect the monochromatic kaon decay-at-rest neutrinos from J-PARC after they have travelled several hundred kilometers and undergone oscillations. This measurement will serve as a valuable cross-check in constraining our understanding of neutrino oscillations in a new regime of neutrino energy and baseline length. We also study the expected event rates from pion and muon DAR neutrinos in liquid Argon and water detectors and their sensitivities to to the CP violating phase ${\delta }_{\mathrm{CP}}$.

    hep-phhep-exPRD(2020)·10 citations
19. 19*

    Safe Use of Jet Pull

    Andrew Larkoski🇺🇸 · Simone Marzani🇮🇹 · Chang Wu🇮🇹

    Jet pull is an observable designed to probe colour flow between jets. Thus far, a particular projection of the pull vector, the pull angle, has been employed to distinguish colour flow between jets produced by a colour singlet or an octet decay. This is of particular importance in order to separate the decay of a Higgs boson to a pair of bottom quarks from the QCD background. However, the pull angle is not infra-red and collinear (IRC) safe. In this paper we introduce IRC safe projections of the pull vector that exhibit good sensitivity to colour flow, while maintaining calculability. We calculate these distributions to next-to-leading logarithmic accuracy, in the context of the hadronic decay of a Higgs boson, and compare these results to Monte Carlo simulations. This study allows us to define an IRC safe version of the pull angle in terms of asymmetry distributions. Furthermore, because of their sensitivity to wide-angle soft radiation, we anticipate that these asymmetries can play an important role in assessing subleading colour correlations and their modelling in general-purpose Monte Carlo parton showers.

    hep-phJHEP(2020)·11 citations
20. 20*

    Kinetic equations for sterile neutrinos from thermal fluctuations

    Dietrich Bodeker🇩🇪 · Dennis Schroder🇩🇪

    We obtain non-linear kinetic equations for sterile neutrino occupancies and lepton minus baryon numbers by matching real time correlation functions of thermal fluctuations computed in an effective description to those computed in thermal quantum field theory. After expanding in the sterile-neutrino Yukawa couplings, the coefficients in the equations are written as real time correlation functions of Standard Model operators. Our kinetic equations are valid for an arbitrary number of sterile neutrinos of any mass spectrum. They can be used to describe, e.g., low-scale leptogenesis via neutrino oscillations, or sterile neutrino dark matter production in the Higgs phase.

    hep-phastro-ph.COhep-thJCAP(2020)·18 citations
21. 21*

    Mass varying neutrinos with different quintessence potentials

    Sayan Mandal🇺🇸 · Gennady Y. Chitov🇨🇦 · Olga Avsajanishvili🇬🇪 · Bijit Singha🇺🇸 · Tina Kahniashvili🇺🇸

    The mass-varying neutrino scenario is analyzed for three trial quintessence potentials (Ferreira-Joyce, inverse exponential, and thawing oscillating). The neutrino mass is generated via Yukawa coupling to the scalar field which represents dark energy. The inverse exponential and oscillating potentials are shown to successfully generate the neutrino masses in the range $m\sim 10^{-2}-10^{-3}$eV and to yield the current dark energy density in the regime of the late-time acceleration of the Universe. Depending on the choice of potentials, the acceleration could occur in two different regimes: (1) the regime of instability, and (2) the stable regime. The first regime of instability is after the Universe underwent a first-order transition and is rolling toward the new stable vacuum. The imaginary sound velocity $c_s^2<0$ in this regime implies growing fluctuations of the neutrino density (clustering). In the second regime, the Universe smoothly changes its stable states via a continuous transition. Since $c_s^2>0$, the neutrino density is stable. For all cases the predicted late-time acceleration of the Universe is asymptotically very close to that of the $\Lambda$CDM model. Further extensions of the theory to modify the neutrino sector of the Standard Model and to incorporate inflation are also discussed. It is also shown that in the stable regimes where the neutrino mass is given by the minimum of the thermodynamic potential, the tree-level dynamics of the scalar field is robust with respect to one-loop bosonic and fermionic corrections to the potential.

    hep-phastro-ph.COhep-thJCAP(2021)·10 citations
22. 22*

    Evolution of fluctuations in the initial state of heavy-ion collisions from RHIC to LHC

    Giuliano Giacalone🇫🇷 · François Gelis🇫🇷 · Pablo Guerrero-Rodríguez🇫🇮 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷

    Fluctuations in the initial state of heavy-ion collisions are larger at RHIC energy than at LHC energy. This fact can be inferred from recent measurements of the fluctuations of the particle multiplicities and of elliptic flow performed at the two different energies. We show that an analytical description of the initial energy-density field and its fluctuations motivated by the color glass condensate (CGC) effective theory predicts and quantitatively captures the measured energy evolution of these observables. The crucial feature is that fluctuations in the CGC scale like the inverse of the saturation scale of the nuclei.

    ↳ nucl-thhep-exhep-phnucl-exSpringer Proc.Phys.(2020)·6 citations
23. 23*

    The leading hadronic vacuum polarization contribution to the muon anomalous magnetic moment using $N_f=2+1$ O($a$) improved Wilson quarks

    Antoine Gérardin🇩🇪 · Marco Cè🇩🇪 · Georg von Hippel🇩🇪 · Ben Hörz🇺🇸 · Harvey Meyer🇩🇪 · Daniel Mohler🇩🇪 · Konstantin Ottnad🇩🇪 · Jonas Wilhelm🇩🇪 · Hartmut Wittig🇩🇪

    We present a lattice calculation of the leading hadronic contribution to the anomalous magnetic moment of the muon. This work is based on a subset of the CLS ensembles with $N_f=2+1$ dynamical quarks and a quenched charm quark. Noise reduction techniques are used to improve significantly the statistical precision of the dominant light quark contribution. The main source of systematic error comes from finite size effects which are estimated using the formalism described in Ref. [7] and based on our knowledge of the timelike pion form factor. The strange and charm quark contributions are under control and an estimate of the quark-disconnected contribution is included. Isospin breaking effects will be studied in a future publication but are included in the systematic error using an estimate based on published lattice results. Our final result, $a_{\mu }^{\mathrm{hvp}}=(720.0\pm 12.4\pm 6.8)\times 10^{-10}$, has a precision of about 2%.

    ↳ hep-lathep-phPoS(2019)·2 citations
24. 24*

    Excited light baryons from quark-gluon-level calculations

    J. Segovia🇪🇸 · C. Chen🇩🇪 · Z.-F. Cui🇨🇳 · Y. Lu🇨🇳 · C.D. Roberts🇨🇳

    The task of mapping and explaining the spectrum of baryons and the structure of these states in terms of quarks and gluons is a longstanding challenge in hadron physics, which is likely to persist for another decade or more. We review the progress made in this topic using a functional method based on Dyson-Schwinger equations. This framework provides a non-perturbative, Poincaré-covariant continuum formulation of Quantum Chromodynamics which is able to extract novel insight on baryon properties since the physics at the hadron level is directly related with the underlying quark-gluon substructure, via convolution of Green functions.

    ↳ nucl-thhep-lathep-ph1 citation
25. 25*

    Magnetic fields from cosmological bulk flows

    J. A. R. Cembranos🇪🇸 · A. L. Maroto🇪🇸 · H. Villarrubia-Rojo🇪🇸

    We explore the possibility that matter bulk flows could generate the required vorticity in the electron-proton-photon plasma to source cosmic magnetic fields through the Harrison mechanism. We analyze the coupled set of perturbed Maxwell and Boltzmann equations for a plasma in which the matter and radiation components exhibit relative bulk motions at the background level. We find that, to first order in cosmological perturbations, bulk flows with velocities compatible with current Planck limits ($\beta <8.5\times 10^{-4}$ at $95\%$ CL) could generate magnetic fields with an amplitude $10^{-21}$ G on 10 kpc comoving scales at the time of completed galaxy formation which could be sufficient to seed a galactic dynamo mechanism.

    ↳ astro-ph.COastro-ph.GAgr-qchep-phMNRAS(2020)·5 citations
26. 26*

    Synergies across the spectrum for particle dark matter indirect detection: how HI intensity mapping meets gamma rays

    Elena Pinetti🇫🇷 · Stefano Camera🇮🇹 · Nicolao Fornengo🇮🇹 · Marco Regis🇮🇹

    Neutral hydrogen (HI) intensity mapping traces the large-scale distribution of matter in the Universe and therefore should correlate with the gamma-ray emission originated from particle dark matter annihilation or from active galactic nuclei and star-forming galaxies, since the related processes occur in the same cosmic structures hosting HI. In this paper, we derive the cross-correlation signal between the brightness temperature of the 21-cm line emission of the HI spin-flip transition in the Universe and the unresolved gamma-ray background. Specifically, we derive forecasts for the cross-correlation signal by focussing on the opportunities offered by the combination of the Fermi-Large Area Telescope (LAT) gamma-ray sensitivity with the expectations of the HI intensity mapping measurements from future radio telescopes, for which we concentrate on the Square Kilometre Array (SKA) and MeerKAT, one of its precursors. We find that the combination of MeerKAT with the current Fermi-LAT statistics has the potential to provide a first hint of the cross-correlation signal originated by astrophysical sources, with a signal-to-noise ratio (SNR) of 3.7. With SKA Phase 1 and SKA Phase 2, the SNR is predicted to increase up to 5.7 and 8.2, respectively. The bounds on dark matter properties attainable with SKA combined with the current statistics of Fermi-LAT are predicted to be comparable to those obtained from other techniques able to explore the unresolved components of the gamma-ray background. The enhanced capabilities of SKA Phase 2, combined with a future generation gamma-ray telescope with improved specifications, can allow us to investigate the whole mass window for weakly interacting massive particles up to the TeV scale.

    ↳ astro-ph.COhep-phJCAP(2020)·17 citations

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