Wed·Apr 3, 2019Wednesday·April 3, 2019

1. 01*

   Isolated photon and photon+jet production at NNLO QCD accuracy

   Xuan Chen🇨🇭 · Thomas Gehrmann🇨🇭 · Nigel Glover🇬🇧 · Marius Höfer🇨🇭 · Alexander Huss🇨🇭

   We describe the calculation of the next-to-next-to-leading order (NNLO) QCD corrections to isolated photon and photon-plus-jet production, and discuss how the experimental hadron-level photon definition and isolation criteria can be approximated in the theoretical parton-level calculation. The NNLO corrections lead to a considerable reduction of the theory uncertainty on the predictions, typically to less than five per cent, and enable an improved description of experimental measurements from ATLAS and CMS.

   hep-phJHEP(2020)·91 citations
2. 02*

   Effects of the QCD Equation of State and Lepton Asymmetry on Primordial Gravitational Waves

   Fazlollah Hajkarim🇩🇪 · Jürgen Schaffner-Bielich🇩🇪 · Stephan Wystub🇩🇪 · Mandy M. Wygas🇩🇪

   Using the quantum chromodynamics (QCD) equation of state (EoS) from lattice calculations we investigate effects from QCD on primordial gravitational waves (PGWs) produced during the inflationary era. We also consider different cases for vanishing and nonvanishing lepton asymmetry where the latter one is constrained by cosmic microwave background experiments. Our results show that there is up to a few percent deviation in the predicted gravitational wave background in the frequency range around the QCD transition ($10^{-10}-10^{-7}$~Hz) for different lattice QCD EoSs, or at larger frequencies for nonvanishing lepton asymmetry using perturbative QCD. Future gravitational wave experiments with high enough sensitivity in the measurement of the amplitude of PGWs like SKA, EPTA, DECIGO and LISA can probe these differences and can shed light on the real nature of the cosmic QCD transition and the existence of a nonvanishing lepton asymmetry in the early universe.

   hep-phastro-ph.COgr-qchep-latPRD(2019)·21 citations
3. 03*

   CP violation and material interaction of neutral kaons in measurements of the CKM angle $\gamma$ using $B^{\pm }\to D{K}^{\pm }$ decays where $D\to K_{\text{S}}^0{\pi }^{+}{\pi }^{-}$

   Mikkel Bjørn🇬🇧 · Sneha Malde🇬🇧

   As measurements of the CKM angle $\gamma$ in decays of $b$-hadrons become increasingly precise, it is important to consider the impact of processes that affect secondary and tertiary decay products and can contribute to the observed CP violation. The golden decay mode used to measure $\gamma$ is $B^{\pm }\to D{K}^{\pm }$, where $D\to K_{\text{S}}^0{\pi }^{+}{\pi }^{-}$. Due to the presence of a $K_{\text{S}}^0$ meson in the final state, $\gamma$ measurements based on this mode are affected by neutral kaon CP violation and matter regeneration, and this study examines the potential size of the impact. Previous studies determine the impact of kaon CP violation to be a few degrees in size, but make simplifying assumptions about how experimental measurements are implemented. These assumptions are lifted in the present study, and the matter regeneration effect is included for the first time. The results are presented within the context of $\gamma$ measurements to be made using the LHCb and Belle II II detectors. It is found that the expected biases due to ignoring the effects of CP violation and matter regeneration in neutral kaons is small and less than $0.5^{\circ }$ degrees in all experimental scenarios considered.

   hep-phJHEP(2019)·20 citations
4. 04*

   Quantized first-order phase transition and two sets of critical end point in droplet quark matter

   Kun Xu🇨🇳 · Mei Huang🇨🇳

   The finite-size effect on the chiral phase transition is investigated in the Nambu--Jona-Lasinio model. To take into account finite-size effects, momentum integrals are replaced by momentum summations. The ground state of quark matter at finite size is favored when applying the periodic spatial boundary condition for quarks. The zero-momentum contribution is taken into account in the periodic boundary condition, and its contribution becomes important when the system size is comparable with the pion wavelength. When the zero-mode contribution becomes dominant, the conventional first-order chiral phase transition at high baryon chemical potential splits into two first-order phase transitions in small system of quark matter, and two sets of critical end point show up in the temperature and chemical potential plane.

   hep-phhep-latnucl-thPoS(2019)·5 citations
5. 05*

   Chasing after flavor symmetries of quarks from bottom up

   Yoshiharu Kawamura🇯🇵

   We explore a flavor structure of quarks in the standard model under the assumption that flavor symmetries exist in a theory beyond the standard model, and chase after their properties, using a bottom-up approach. We reacknowledge that a flavor-symmetric part of Yukawa coupling matrix can be realized by a rank-one matrix and a democratic-type one occupies a special position, based on Dirac's naturalness.

   hep-phhep-thPTEP(2019)·3 citations
6. 06*

   Light-by-light scattering in ultra-peripheral heavy-ion collisions at low diphoton masses

   Mariola Klusek-Gawenda🇵🇱 · Ronan McNulty🇮🇪 · Rainer Schicker🇩🇪 · Antoni Szczurek🇵🇱

   We present a study of photon-photon scattering in the mass range $W_{\gamma \gamma }<5$ GeV. We extend earlier calculations of this cross section for $W_{\gamma \gamma }>$ 5 GeV into the low mass range where photoproduction of the pseudoscalar resonances $\eta$, ${\eta }^{{}^{\prime }}(958)$ contributes to two-photon final states. We present the elementary photon-photon cross section as a function of diphoton mass $M_{\gamma \gamma }$ arising from lepton and quark loop diagrams, and the visible cross section obtained with the gamma-gamma decay branching fractions of the resonances $\eta$, ${\eta }^{{}^{\prime }}(958)$, ${\eta }_c(1S)$, ${\eta }_c(2S)$, ${\chi }_{c0}(1P)$. We derive the corresponding cross sections in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV by folding the elementary cross section with the heavy-ion photon fluxes. We consider the dominating background of the two-photon final state which arises from gamma decays of photoproduced ${\pi }^0$-pairs. Such ${\pi }^0$-pairs contribute to the background when only two of the four decay photons are within the experimental acceptance, while the other two photons escape undetected. We reduce this background by applying cuts on asymmetries of transverse momenta of the two photons and indicate how the background can be further suppressed using a multivariate sideband analysis. We present the cross section for the signal and the background at midrapidity $|\eta |<$ 0.9, and in the forward rapidity range 2.0 $<\eta <$ 4.5.

   hep-phPRD(2019)·42 citations
7. 07*

   Heavy quark spin symmetric molecular states from ${\bar{D}}^{(\ast )}{\Sigma }_c^{(\ast )}$ and other coupled channels in the light of the recent LHCb pentaquarks

   C. W. Xiao🇨🇳 · J. Nieves🇪🇸 · E. Oset🇪🇸

   We consider the ${\bar{D}}^{(\ast )}{\Sigma }_c^{(\ast )}$ states, together with $J/\psi N$ and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as $1/2^{-}$ $\bar{D}{\Sigma }_c$, $1/2^{-}$ ${\bar{D}}^{\ast }{\Sigma }_c$, and $3/2^{-}$ ${\bar{D}}^{\ast }{\Sigma }_c$, and isospin $I=1/2$. We find another state around 4374 MeV, of $3/2^{-}$ $\bar{D}{\Sigma }_c^{\ast }$ structure, for which indications appear in the experimental spectrum. Two other near degenerate states of $1/2^{-}$ ${\bar{D}}^{\ast }{\Sigma }_c^{\ast }$ and $3/2^{-}$ ${\bar{D}}^{\ast }{\Sigma }_c^{\ast }$ nature are also found around 4520 MeV, which although less clear, are not incompatible with the observed spectrum. In addition, a $5/2^{-}$ ${\bar{D}}^{\ast }{\Sigma }_c^{\ast }$ state at the same energy appears, which however does not couple to $J/\psi p$ in $S-$wave, and hence it is not expected to show up in the LHCb experiment.

   hep-phhep-exPRD(2019)·222 citations
8. 08*

   On the validity of perturbative studies of the electroweak phase transition in the Two Higgs Doublet model

   Kimmo Kainulainen🇫🇮 · Venus Keus🇫🇮 · Lauri Niemi🇫🇮 · Kari Rummukainen🇫🇮 · Tuomas V.I. Tenkanen🇨🇭 · Ville Vaskonen🇬🇧

   Making use of a dimensionally-reduced effective theory at high temperature, we perform a nonperturbative study of the electroweak phase transition in the Two Higgs Doublet model. We focus on two phenomenologically allowed points in the parameter space, carrying out dynamical lattice simulations to determine the equilibrium properties of the transition. We discuss the shortcomings of conventional perturbative approaches based on the resummed effective potential - regarding the insufficient handling of infrared resummation but also the need to account for corrections beyond 1-loop order in the presence of large scalar couplings - and demonstrate that greater accuracy can be achieved with perturbative methods within the effective theory. We find that in the presence of very large scalar couplings, strong phase transitions cannot be reliably studied with any of the methods.

   hep-phhep-latJHEP(2019)·153 citations
9. 09*

   Fluctuations and clustering of multiplicity in collisions of relativistic ions

   Maciej Rybczynski🇵🇱 · Zbigniew Wlodarczyk🇵🇱

   We discuss the recently measured event-by-event multiplicity fluctuations in relativistic heavy-ion collisions. It is shown that the observed non-monotonic behaviour of the scaled variance of multiplicity distribution as a function of collision centrality (such effect is not observed in a widely used string-hadronic models of nuclear collisions) can be fully explained by the correlations between produced particles promoting cluster formation. We define a cluster as a quasi-neutral gas of charged and neutral particles which exhibits collective behaviour. The characteristic space scale of this shielding is the Debye length. Multiplicity distribution in a cluster is given by Negative Binomial distribution while the rest (reservoir), treated as a superposition of elementary collisions, is described by Binomial distribution. The ability to generate spatial structures (cluster phase) sign the propensity to self-organize of hadronic matter.

   hep-phEPJA(2020)·6 citations
10. 10*

    Wounded nucleon, quark and quark-diquark emission functions versus experimental results from RHIC

    Michał Barej🇵🇱 · Adam Bzdak🇵🇱 · Paweł Gutowski🇵🇱

    Using the wounded nucleon, quark, and quark-diquark models, we extract the wounded source emission functions from the PHOBOS data for d+Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV. We apply these models to compute charged particle multiplicity distributions as functions of pseudorapidity for p+p, p+Al, p+Au, d+Au, ${}^3$He+Au, Cu+Cu, Cu+Au, Au+Au, and U+U collisions at the same energy and compare them with experimental data from the PHOBOS and PHENIX collaborations. In symmetric collisions of heavy nuclei, the obtained distributions differ among the tested models. On the other hand, in asymmetric collisions, all three models give essentially the same distributions. The wounded quark-diquark and quark models are in reasonable agreement with data for all the investigated systems.

    hep-phhep-exnucl-exnucl-thPRC(2019)·9 citations
11. 11*

    Implications of symmetries in the scalar sector

    Howard E. Haber🇺🇸 · O. M. Ogreid🇳🇴 · P. Osland🇳🇴 · M. N. Rebelo🇵🇹

    Symmetries play a very important rôle in Particle Physics. In extended scalar sectors, the existence of symmetries may permit the models to comply with the experimental constraints in a natural way, and at the same time reduce the number of free parameters. There is a strong interplay among internal symmetries of the scalar potential, its CP properties and mass degeneracies of the physical scalars. Some of these aspects were discussed in this talk.

    hep-phJ.Phys.Conf.Ser.(2020)·2 citations
12. 12*

    Phase structure of three flavor QCD in external magnetic fields using HISQ fermions

    Akio Tomiya🇺🇸 · Heng-Tong Ding🇨🇳 · Xiao-Dan Wang🇨🇳 · Yu Zhang🇨🇳 · Swagato Mukherjee🇺🇸 · Christian Schmidt🇩🇪

    We study the phase structure of QCD with three degenerate flavors in the external magnetic fields using highly improved staggered quarks (HISQ). The simulations are performed on $16^3\times 6$ lattice. In order to investigate the quark mass dependence of the chiral transition we choose the values of the bare quark masses 0.015 and 0.0009375 in the lattice unit, corresponding to $m_{\pi }=320$ MeV and 80 MeV in the continuum limit. We found no indication of a first order phase transition in the current window of quark masses and external magnetic fields. Unlike to the case with standard staggered fermions inverse magnetic catalysis is always observed at about the critical temperature. The microscopic origin of this phenomena are further discussed by looking into the Dirac eigenvalue spectrum.

    ↳ hep-lathep-phnucl-thPoS(2019)·24 citations
13. 13*

    Off-diagonal cumulants of net-charge, net-proton and net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7-200 GeV from STAR

    Arghya Chatterjee🇮🇳

    Fluctuations of conserved quantities such as net-baryon, net-charge, and net-strangeness numbers have generated considerable interest in the study of the thermodynamic properties of the hot and dense QCD matter. Theoretical calculations suggest that the off-diagonal cumulants of conserved charges along with the diagonal cumulants can help better constrain the freeze-out parameters and, therefore, help to map the QCD phase diagram. In this proceeding, we briefly outline the recent STAR measurements on the second-order off-diagonal cumulants of net-charge, net-proton, and net-kaon multiplicity distributions in Au+Au collisions from the RHIC BES-I program in the energy range of $\sqrt{s_{NN}}$ = 7.7-200 GeV. The measured cumulant ratios are compared to the predictions from both thermal (HRG) and non-thermal (UrQMD) models.

    ↳ hep-exhep-phnucl-exPoS(2019)·2 citations
14. 14*

    Holographic inflation

    Shin'ichi Nojiri🇯🇵 · Sergei D. Odintsov🇪🇸 · Emmanuel N. Saridakis🇬🇷

    We apply the holographic principle at the early universe, obtaining an inflation realization of holographic origin. Such a consideration has equal footing with its well-studied late-time application, and moreover the decrease of the horizons at early times naturally increases holographic energy density at inflationary scales. Taking as Infrared cutoff the particle or future event horizons, and adding a simple correction due to the Ultraviolet cutoff, whose role is non-negligible at the high energy scales of inflation, we result in a holographic inflation scenario that is very efficient in incorporating inflationary requirements and predictions. We first extract analytically the solution of the Hubble function in an implicit form, which gives a scale factor evolution of the desired e-foldings. Furthermore, we analytically calculate the Hubble slow-roll parameters and then the inflation-related observables, such as the scalar spectral index and its running, the tensor-to-scalar ratio, and the tensor spectral index. Confronting the predictions with Planck 2018 observations we show that the agreement is perfect and in particular deep inside the 1$\sigma$ region.

    ↳ gr-qcastro-ph.COhep-phhep-thPLB(2019)·169 citations
15. 15*

    Nonlinear perturbations from axion-gauge fields dynamics during inflation

    Alexandros Papageorgiou🇺🇸 · Marco Peloso🇮🇹 · Caner Unal🇨🇿

    We study a variant of the Chromo-Natural Inflation (CNI) mechanism in which the inflaton interacts only gravitationally with the CNI fields. Integrating out all the non-dynamical scalar fields of the model results in a coupling between the perturbations of the inflaton and of the CNI pseudo-scalar which is significantly greater than the one obtained in the absence of the gauge CNI dynamics. We compute how this greater coupling impacts the power spectrum of the inflaton perturbations that are sourced nonlinearly by the unstable (tensor) gauge CNI modes, and we require that the amplitude of these modes is well below that of the linear perturbations. Combining this result with various constraints, including backreaction effects, the requirement of having observable and dominant sourced gravitational waves (GW), and the current upper bound on the tensor-to-scalar ratio, significantly constrains the range of parameter space where this model can produce an interesting GW signal.

    ↳ astro-ph.COhep-phhep-thJCAP(2019)·60 citations
16. 16*

    Merger of compact stars in the two-families scenario

    Roberto De Pietri🇮🇹 · Alessandro Drago🇮🇹 · Alessandra Feo🇮🇹 · Giuseppe Pagliara🇮🇹 · Michele Pasquali🇮🇹 · Silvia Traversi🇮🇹 · Grzegorz Wiktorowicz🇨🇳

    We analyse the phenomenological implications of the two-families scenario on the merger of compact stars. That scenario is based on the coexistence of both hadronic stars and strange quark stars. After discussing the classification of the possible mergers, we turn to detailed numerical simulations of the merger of two hadronic stars, i.e., "first family" stars in which delta resonances and hyperons are present, and we show results for the threshold mass of such binaries, for the mass dynamically ejected and the mass of the disk surrounding the post-merger object. We compare these results with those obtained within the one-family scenario and we conclude that relevant signatures of the two-families scenario can be suggested, in particular: the possibility of a rapid collapse to a black hole for masses even smaller than the ones associated to GW170817; during the first milliseconds, oscillations of the postmerger remnant at frequencies higher than the ones obtained in the one-family scenario; a large value of the mass dynamically ejected and a small mass of the disk, for binaries of low total mass. Finally, based on a population synthesis analysis, we present estimates of the number of mergers for: two hadronic stars; hadronic star - strange quark star; two strange quark stars. We show that for unequal mass systems and intermediate values of the total mass, the merger of a hadronic star and a strange quark star is very likely (GW170817 has a possible interpretation into this category of mergers). On the other hand, mergers of two strange quark stars are strongly suppressed.

    ↳ astro-ph.HEastro-ph.SRhep-phnucl-thApJ(2019)·71 citations
17. 17*

    Dark Matter that Interacts with Baryons: Experimental Limits on the Interaction Cross-section for 27 Atomic Nuclei, and Resultant Constraints on the Particle Properties

    David A. Neufeld (JHU)🇺🇸 · Daniel J. Brach-Neufeld

    To constrain the properties of dark matter (DM) that interacts with nucleons, we have conducted an experimental search for any anomalous heating of ordinary baryonic matter at 77 K. Our tabletop experiment is motivated by the possibility (discussed in a previous paper) that DM particles with masses in the $\sim 1-2m_{\mathrm{p}}$ range could be captured by and concentrated within the Earth. For suitable parameters, this phenomenon could lead to a substantial density $\sim 10^{14}\mathrm{c}{\mathrm{m}}^{-3}$ of thermalized (300 K) DM particles at Earth's surface that would heat cooler baryonic matter. Our experiment involves precise differential measurements of the evaporation rate of liquid nitrogen in a storage dewar within which various materials are immersed. The results revealed no statistically-significant detections of heating in the 27 elements with molar fractions $>10^{-5}$ in Earth's crust. For material with the average composition of Earth's crust, our measurements imply a $3\sigma$ upper limit of $1.32\times 10^{-27}{n}_{14}^{-1}(m_{\mathrm{DM}}/2m_{\mathrm{p}}{)}^{-1/2}\mathrm{c}{\mathrm{m}}^2$ on the mean cross-section for scattering with thermal HIDM at 300 K, where $10^{14}{n}_{14}\mathrm{c}{\mathrm{m}}^{-3}$ is the particle density at Earth's surface. In combination with a lower limit on the scattering cross-section, obtained from a consideration of the heat flow through the Earth's crust (Neufeld, Farrar & McKee 2018), our experiment places an upper limit of $1.6\times 10^{13}\mathrm{c}{\mathrm{m}}^{-3}$ on the density of DM at the Earth's surface. This in turn, significantly constrains the properties for any DM candidate that interacts with baryons.

    ↳ astro-ph.COhep-phApJ(2019)·11 citations
18. 18*

    Pushing the Energy and Cosmic Frontiers with High-Energy Astrophysical Neutrinos

    Mauricio Bustamante (Bohr Inst. & Copenhagen U.)🇩🇰

    The astrophysical neutrinos recently discovered by the IceCube neutrino telescope have the highest detected neutrino energies --- from TeV to PeV --- and travel the longest distances --- up to a few Gpc, the size of the observable Universe. These features make them naturally attractive probes of fundamental particle-physics properties, possibly tiny in size, at energy scales unreachable by any other means. The decades before the IceCube discovery saw many proposals of particle-physics studies in this direction. Today, those proposals have become a reality, in spite of prevalent astrophysical unknowns. We showcase examples of studying fundamental neutrino physics at these scales, including some of the most stringent tests of physics beyond the Standard Model.

    ↳ astro-ph.HEastro-ph.COhep-phJ.Phys.Conf.Ser.(2020)·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.