Thu·Nov 1, 2018Thursday·November 1, 2018

1. 01*

   QCD at finite temperature and chemical potential from Dyson-Schwinger equations

   Christian S. Fischer🇩🇪

   We review results for the phase diagram of QCD, the properties of quarks and gluons and the resulting properties of strongly interacting matter at finite temperature and chemical potential. The interplay of two different but related transitions in QCD, chiral symmetry restoration and deconfinement, leads to a rich phenomenology when external parameters such as quark masses, volume, temperature and chemical potential are varied. We discuss the progress in this field from a theoretical perspective, focusing on non-perturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We aim at a pedagogical overview on the physics associated with the structure of this framework and explain connections to other approaches, in particular with the functional renormalization group and lattice QCD. We discuss various aspects associated with the variation of the quark masses, assess recent results for the QCD phase diagram including the location of a putative critical end-point for $N_f=2+1$ and $N_f=2+1+1$, discuss results for quark spectral functions and summarise aspects of QCD thermodynamics and fluctuations.

   hep-phhep-latnucl-thPPNP(2019)·387 citations
2. 02*

   Two-loop perturbative corrections to the constrained effective potential in thermal QCD

   Yun Guo🇨🇳 · Qianqian Du🇨🇳

   In this paper, we compute the constrained QCD effective potential up to two-loop order with finite quark mass and chemical potential. We present the explicit calculations by using the double line notation and analytical expressions for massless quarks are obtained in terms of the Bernoulli polynomials or Polyakov loops. Our results explicitly show that the constrained QCD effective potential is independent on the gauge fixing parameter. In addition, as compared to the massless case, the constrained QCD effective potential with massive quarks develops a completely new term which is only absent when the background field vanishes. Furthermore, we discuss the relation between the one- and two-loop constrained effective potential. The surprisingly simple proportionality that exists in the pure gauge theories, however, is in general no longer true when fermions are taken into account. On the other hand, for high baryon density ${\mu }_B$ and low temperature $T$, in the massless limit, we do also find a similar proportionality between the one- and two-loop fermionic contributions in the constrained effective potential up to $\mathcal{O}(T/{\mu }_B)$.

   hep-phhep-thJHEP(2019)·26 citations
3. 03*

   Surface tension of dense matter at the chiral phase transition

   Eduardo S. Fraga🇧🇷 · Maurício Hippert🇧🇷 · Andreas Schmitt🇬🇧

   If a first-order phase transition separates nuclear and quark matter at large baryon density, an interface between these two phases has a nonzero surface tension. We calculate this surface tension within a nucleon-meson model for domain walls and bubbles. Various methods and approximations are discussed and compared, including a numerical evaluation of the spatial profile of the interface. We also compute the surface tension at the other first-order phase transitions of the model: the nuclear liquid-gas transition and, in the parameter regime where it exists, the direct transition from the vacuum to the (approximately) chirally symmetric phase. Identifying the chirally symmetric phase with quark matter - our model does not contain explicit quark degrees of freedom - we find maximal surface tensions of the vacuum-quark transition ${\Sigma }_{\mathrm{VQ}}\sim 15\mathrm{MeV}/{\mathrm{fm}}^2$, relevant for the surface of quark stars, and of the nuclear-quark transition ${\Sigma }_{\mathrm{NQ}}\sim 10\mathrm{MeV}/{\mathrm{fm}}^2$, relevant for hybrid stars and for quark matter nucleation in supernovae and neutron star mergers.

   hep-phastro-ph.HEnucl-thPRD(2019)·55 citations
4. 04*

   $CP$ violation in $\eta$ muonic decays

   Pablo Sanchez-Puertas🇪🇸

   In this study, we investigate the imprints of $CP$ violation in certain $\eta$ muonic decays that could arise within the Standard Model effective field theory. In particular, we study the sensitivities that could be reached at REDTOP, a proposed $\eta$ facility. After estimating the bounds that the neutron EDM places, we find still viable to discover signals of $CP$ violation via the muons' polarization in $\eta \to {\mu }^{+}{\mu }^{-}$ decays at REDTOP, with a single effective operator as its plausible source.

   hep-phJHEP(2019)·22 citations
5. 05*

   SMASH-ing Vacuum Metastability

   C.R. Das🇷🇺 · Katri Huitu🇫🇮 · Timo J. Karkkainen🇫🇮

   Five fundamental problems - neutrino oscillations, baryogenesis, dark matter, inflation, strong CP problem - are solved at one stroke in "SM-A-S-H" (Standard Model-Axion-Seesaw-Higgs portal inflation) model by Andreas Ringwald et. al. The Standard Model (SM) particle content was extended by three right-handed SM-singlet neutrinos $N_i$, a vector-like color triplet quark $Q$, a complex SM-singlet scalar field $\sigma$ that stabilises the Higgs potential, all of them being charged under a global lepton number (hyper-charge) and Peccei-Quinn (PQ) $U(1)$ symmetry. We found numerically that SMASH model not only solves five fundamental problems but also the sixth problem "Vacuum Metastability" through the extended scalar sector.

   hep-ph0 citations
6. 06*

   Bottomonium spectroscopy motivated by general features of pNRQCD

   Raghav Chaturvedi🇮🇳 · Ajay Kumar Rai🇮🇳 · Nakul R. Soni🇮🇳 · Jignesh N. Pandya🇮🇳

   The bottomonium mass spectra is computed in the framework of potential non-relativistic quantum chromodynamics. The potential consists of a static term incorporating Coulombic plus confinement part along with a correction term added non-perturbatively from pNRQCD, which is classified in powers of the inverse of heavy quark mass \textit{O}$(1/m)$. The masses of excited bottomonia are calculated by perturbatively adding spin-hyperfine, spin-orbit and tensor components of one gluon exchange interactions in powers of \textit{O}$(1/m^2)$. Calculated masses are found to be consistent with other theoretical studies and experimental data. The Regge trajectories of the calculated mass spectra are also constructed. The values of the wave-functions are extracted and employed to calculate the electromagnetic transition widths and $\gamma \gamma$, $e^{+}{e}^{-}$, light hadron and $\gamma \gamma \gamma$ decay widths of several states at various leading orders, within the non-relativistic QCD formalism. Some of the experimentally reported states of bottomonium family like ${\rm Y}$(10860), ${\rm Y}$(11020) and X(10610) are identified as mixed $S-D$ wave and $P$-wave states.

   hep-phJ.Phys.G(2020)·26 citations
7. 07*

   The role of temperature dependent string-inspired CPT violating backgrounds in leptogenesis and the chiral magnetic effect

   Thomas Bossingham🇬🇧 · Nick E. Mavromatos🇬🇧 · Sarben Sarkar🇬🇧

   In a temperature dependent CPT-Violating (CPTV) axial time-like background (induced by the Kalb-Ramond tensor field of string theory) we discuss leptogenesis by solving the Boltzmann equation.The current work non-trivially modifies the framework of a previous phenomenological approach by the authors where the CPTV axial background was considered to be a constant (with no microscopic justification). The constant background approximation though is shown to capture the main phenomenological features of leptogenesis. On comparing our analysis to the related chiral magnetic effect for axial current condensates, we conclude that the Kalb-Ramond field does not play the role of the chiral chemical potential needed for that effect.

   hep-phgr-qchep-thEPJC(2019)·40 citations
8. 08*

   Basis-invariant conditions for CP symmetry of order 4

   Igor P. Ivanov🇵🇹 · Celso C. Nishi🇧🇷 · Joao P. Silva🇵🇹 · Andreas Trautner🇩🇪

   Three-Higgs-doublet models (3HDM) allow for a novel, physically distinct form of CP invariance: CP symmetry of order 4 (CP4). Due to the large basis change freedom in 3HDM, it is imperative to recognize the presence of a possibly hidden CP4 in a basis-invariant way. In the present work, we solve this problem and establish basis-invariant necessary and sufficient conditions for a 3HDM to possess a CP4 symmetry. We also derive a basis-invariant criterion to decide whether or not a CP4 symmetric 3HDM possesses any additional CP symmetry, as well as a criterion to decide whether or not CP4 is spontaneously broken.

   hep-phPRD(2019)·21 citations
9. 09*

   A Symmetric Two Higgs Doublet Model

   Hannah Bossi🇺🇸 · Shreyashi Chakdar🇺🇸

   After the discovery of a SM-like scalar state with mass of 125 GeV in 2012, the electroweak sector demands to be studied with all possible theoretical and experimental efforts. In this work we present a symmetric two Higgs doublet model with a discrete interchange symmetry between the two Higgs doublets (${\Phi }_1$ $\leftrightarrow$ ${\Phi }_2$). Apart from the SM-like scalar state (h) with $m_h=125$ GeV, the model has several distinguishing features including the pseudoscalar (A), the charged scalars($H^{\pm }$) and the neutral scalar H, which do not have any direct coupling to fermions. The neutral scalar $H$ can have mass lighter than the 125 GeV SM-like Higgs state $h$. Due to the presence of a residual $Z_2$ symmetry after the Spontaneous Symmetry Breaking (SSB), the neutral scalar $H$ emerges as the Dark Matter candidate in this scenario. As an effect of this possibility, the SM-like scalar $h$ will have an extra invisible decay mode of $h\to HH$ in this framework. We propose the model and discuss some of the interesting features with a guideline of possible phenomenological searches at the LHC present in this scenario.

   hep-phVol. 7 No. 3 (2021): Special Issue: ANPA …·0 citations
10. 10*

    Aligned and Spontaneous Flavor Violation

    Daniel Egana-Ugrinovic🇺🇸 · Samuel Homiller🇺🇸 · Patrick Meade🇺🇸

    We present a systematic spurion setup called Aligned Flavor Violation (AFV) that allows for new physics couplings to quarks that are aligned with the Standard Model (SM) Yukawas, but do not necessarily share their hierarchies nor are family universal. Additionally, we show that there is an important subset of AFV called Spontaneous Flavor Violation (SFV), which naturally arises from UV completions where the quark family number and CP groups are spontaneously broken. Flavor-changing neutral currents are strongly suppressed in SFV extensions of the SM. We study SFV from an effective field theory perspective and demonstrate that SFV new physics with significant and preferential couplings to first or second generation quarks may be close to the TeV scale.

    hep-phPRL(2019)·77 citations
11. 11*

    Determining the Nonperturbative Collins-Soper Kernel From Lattice QCD

    Markus A. Ebert🇺🇸 · Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸

    At small transverse momentum $q_T$, transverse-momentum dependent parton distribution functions (TMDPDFs) arise as genuinely nonperturbative objects that describe Drell-Yan like processes in hadron collisions as well as semi-inclusive deep-inelastic scattering. TMDPDFs naturally depend on the hadron momentum, and the associated evolution is determined by the Collins-Soper equation. For $q_T\sim {\Lambda }_{\mathrm{QCD}}$ the corresponding evolution kernel (or anomalous dimension) is nonperturbative and must be determined as an independent ingredient in order to relate TMDPDFs at different scales. We propose a method to extract this kernel using lattice QCD and the Large-Momentum Effective Theory, where the physical TMD correlation involving light-like paths is approximated by a quasi TMDPDF, defined using equal-time correlation functions with a large-momentum hadron state. The kernel is determined from a ratio of quasi TMDPDFs extracted at different hadron momenta.

    hep-phhep-latnucl-thPRD(2019)·129 citations
12. 12*

    Neutrinoless Double-$\beta$ Decay with Nonstandard Majoron Emission

    Ricardo Cepedello🇪🇸 · Frank F. Deppisch🇬🇧 · Lorena González🇬🇧 · Chandan Hati🇫🇷 · Martin Hirsch🇪🇸

    We present a novel mode of neutrinoless double beta decay with emission of a light Majoron-like scalar particle phi. We assume it couples via an effective seven-dimensional operator with a (V+A) lepton current and (V+-A) quark currents leading to a long-range contribution that is unsuppressed by the light neutrino mass. We calculate the total double beta decay rate and determine the fully differential shape for this mode. We find that future double beta decay searches are sensitive to scales of the order Lambda_NP ~ 1 TeV for the effective operator and a light scalar m_phi < 0.2 MeV, based on ordinary double beta decay Majoron searches. The angular and energy distributions can deviate considerably from that of two-neutrino double beta decay, which is the main background. We point out possible ultraviolet completions where such an effective operator can emerge.

    hep-phPRL(2019)·37 citations
13. 13*

    Improved limits on Lorentz invariance violation from astrophysical gamma-ray sources

    Rodrigo Guedes Lang🇧🇷 · Humberto Martínez-Huerta🇧🇷 · Vitor de Souza🇧🇷

    Lorentz invariance (LI) has a central role in science and its violation (LIV) at some high-energy scale has been related to possible solutions for several of the most intriguing puzzles in nature such as dark matter, dark energy, cosmic rays generation in extreme astrophysical objects and quantum gravity. We report on a search for LIV signal based on the propagation of gamma rays from astrophysical sources to Earth. An innovative data analysis is presented which allowed us to extract unprecedented information from the most updated data set composed of 111 energy spectra of 38 different sources measured by current gamma-ray observatories. No LIV signal was found, and we show that the data are best described by LI assumption. We derived limits for the LIV energy scale at least 3 times better than the ones currently available in the literature for subluminal signatures of LIV in high-energy gamma rays.

    ↳ astro-ph.HEgr-qchep-phPRD(2019)·66 citations
14. 14*

    Statistical analysis of binary stars from the Gaia catalogue DR2

    Petr Zavada🇨🇿 · Karel Píška🇨🇿

    We have developed a general statistical procedure for analysis of 2D and 3D finite patterns, which is applied to the data from recently released Gaia-ESA catalogue DR2. The 2D analysis clearly confirms our former results on the presence of binaries in the former DR1 catalogue. Our main objective is the statistical 3D analysis of DR2. For this, it is essential that the DR2 catalogue includes parallaxes and data on the proper motion. The analysis allows us to determine for each pair of stars the probability that it is the binary star. This probability is represented by the function \b{eta}({\Delta}) depending on the separation. Further, a combined analysis of the separation with proper motion provides a clear picture of binaries with two components of the motion: parallel and orbital. The result of this analysis is an estimate of the average orbital period and mass of the binary system. The catalogue we have created involves 80560 binary candidates.

    ↳ astro-ph.IMastro-ph.SRhep-phAstron.J.(2020)·3 citations
15. 15*

    Computation of hybrid static potentials from optimized trial states in SU(3) lattice gauge theory

    Christian Reisinger🇩🇪 · Stefano Capitani🇩🇪 · Lasse Müller🇩🇪 · Owe Philipsen🇩🇪 · Marc Wagner🇩🇪

    We compute hybrid static potentials in SU(3) lattice gauge theory using a method to automatically generate a large set of suitable creation operators from elementary building blocks. This method allows to find sets of creation operators, which generate trial states with large ground state overlaps for all investigated angular momentum and parity sectors. We present numerical results for hybrid static potentials with quantum numbers ${\Sigma }_g^{-},{\Sigma }_u^{+},{\Sigma }_u^{-},{\Pi }_g,{\Pi }_u,{\Delta }_g,{\Delta }_u$.

    ↳ hep-lathep-phPoS(2018)·8 citations
16. 16*

    Mass Splitting in a Linear Sigma Model

    Diego de Floor🇺🇸 · Erik Gustafson🇺🇸 · Yannick Meurice🇺🇸

    We derived the tree level spectrum to an extension to the linear sigma model describing an EFT for an $SU(3{)}_c$ gauge theory with $N_f$ flavors of fermions and $N_1$ fermions have a mass $m_l$ and $N_2$ fermions have a mass $m_h$. We examined the effects of a small mass splitting on single mass data for 8 and 12 flavors of fermions corresponding to the unperturbed case. Our intention is to encourage more simulations of split mass theories with 8, 10 and 12 flavors of fermions.

    ↳ hep-lathep-phhep-thPoS(2019)·1 citation
17. 17*

    The Cosmological Bootstrap: Inflationary Correlators from Symmetries and Singularities

    Nima Arkani-Hamed🇺🇸 · Daniel Baumann🇳🇱 · Hayden Lee🇺🇸 · Guilherme L. Pimentel🇳🇱

    Scattering amplitudes at weak coupling are highly constrained by Lorentz invariance, locality and unitarity, and depend on model details only through coupling constants and particle content. In this paper, we develop an understanding of inflationary correlators which parallels that of flat-space scattering amplitudes. Specifically, we study slow-roll inflation with weak couplings to extra massive particles, for which all correlators are controlled by an approximate conformal symmetry on the boundary of the spacetime. After classifying all possible contact terms in de Sitter space, we derive an analytic expression for the four-point function of conformally coupled scalars mediated by the tree-level exchange of massive scalars. Conformal symmetry implies that the correlator satisfies a pair of differential equations with respect to spatial momenta, encoding bulk time evolution in purely boundary terms. The absence of unphysical singularities completely fixes this correlator. A spin-raising operator relates it to the correlators associated with the exchange of particles with spin, while weight-shifting operators map it to the four-point function of massless scalars. We explain how these de Sitter four-point functions can be perturbed to obtain inflationary three-point functions. We reproduce many classic results in the literature and provide a complete classification of all inflationary three- and four-point functions arising from weakly broken conformal symmetry. The inflationary bispectrum associated with the exchange of particles with arbitrary spin is completely characterized by the soft limit of the simplest scalar-exchange four-point function of conformally coupled scalars and a series of contact terms. Finally, we demonstrate that the inflationary correlators contain flat-space scattering amplitudes via a suitable analytic continuation of the external momenta.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2020)·516 citations
18. 18*

    Ballistic Dark Matter oscillates above $\Lambda$CDM

    Anirban Das (Tata Inst.)🇮🇳 · Basudeb Dasgupta (Tata Inst.)🇮🇳 · Rishi Khatri (Tata Inst.)🇮🇳

    Dark matter may have been relativistic and collisional until relatively late times and become cold and collisionless after a phase transition before the matter-radiation equality of the standard $\Lambda$CDM cosmology. We show that such a dark matter has large peculiar velocities due to acoustic oscillations before the phase transition, and evolves ballistically after the phase transition in the collisionless phase until the initial acoustic velocities are redshifted away. We show that this Ballistic Dark Matter (BDM) results in new non-trivial interesting features in the cosmological observables. In particular, the linear matter power spectrum exhibits acoustic oscillations on scales smaller than the Hubble scale at the time of phase transition, and for fast transitions the power at the acoustic peaks in the matter power spectrum exceeds that in a $\Lambda$CDM cosmology. If BDM only forms a part of the total dark matter, an odd vs. even acoustic peak asymmetry becomes prominent. We give an approximate analytical treatment of the linear perturbations in BDM, explaining these features. We also discuss the possibility to constrain BDM using cosmic microwave background and large scale structure data.

    ↳ astro-ph.COhep-phJCAP(2019)·18 citations
19. 19*

    Probing non-perturbative QED with electron-laser collisions

    C. Baumann🇩🇪 · E. N. Nerush🇷🇺 · A. Pukhov🇩🇪 · I. Yu. Kostyukov🇷🇺

    The vast majority of QED results are obtained in relatively weak fields and so in the framework of perturbation theory. However, forthcoming laser facilities providing extremely high fields can be used to enter not-yet-studied regimes. Here, a scheme is proposed that might be used to reach a supercritical regime of radiation reaction or even the fully non-perturbative regime of quantum electrodynamics. The scheme considers the collision of a 100 GeV-class electron beam with a counterpropagating ultraintense electromagnetic pulse. To reach these supercritical regimes, it is unavoidable to use a pulse with ultrashort duration. Using two-dimensional particle-in-cell simulations, it is therefore shown how one can convert a next-generation optical laser to an ultraintense ($I\approx 2.9\times 10^{24}\text{ W}{\text{cm}}^{-2}$) attosecond (duration $\approx$ 150 as) pulse. It is shown that if the perturbation theory persists in extremely fields, the spectrum of secondary particles can be found semi-analytically. In contrast, a comparison with experimental data may allow differentiating the contribution of high-order radiative corrections if the perturbation theory breaks.

    ↳ physics.plasm-phhep-phSci.Rep.(2019)·53 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.