Thu·Mar 18, 2021Thursday·March 18, 2021

1. 01*

   QCD chiral condensate and pseudoscalar-meson properties in the nuclear medium at finite temperature

   Parada T.P. Hutauruk🇰🇷 · Seung-il Nam🇰🇷

   The pion and kaon properties in a nuclear medium at nonvanishing temperature as well as the QCD chiral condensate in the presence of a magnetic field for various baryon densities are studied in the Nambu-Jona-Lasinio (NJL) model with the help of the proper-time regularization (PTR) scheme, simulating a QCD confinement. The density dependent of the quark mass in symmetric nuclear matter is obtained from the quark-meson coupling (QMC) model, which shares the same covariant feature with the NJL model, at quark level. We then analyze the QCD chiral condensates, and dynamical masses for various baryon densities at finite temperature and magnetic field as well as the pion and kaon masses, pion and kaon weak-decay constants, pion-and kaon-quark coupling constants, and wave function renormalization factors for various baryon densities at finite temperature. We find that the QCD chiral condensates suppress with increasing temperature and baryon density and enhance under the presence of a magnetic field, which are consistent with other model predictions. Interestingly, the wave function renormalization factors for the pion and kaon increase with respect to temperature and reduce as the baryon density increases are found.

   hep-phMod.Phys.Lett.A(2022)·6 citations
2. 02*

   Semi-leptonic form factors of ${\Xi }_c\to \Xi$ in QCD sum rules

   Zhen-Xing Zhao🇨🇳 · Xiao-Yu Sun🇨🇳 · Fu-Wei Zhang🇨🇳 · Yi-Peng Xing🇨🇳 · Ya-Ting Yang🇨🇳

   There exists a significant deviation between the most recent Lattice QCD simulation and experimental measurement by Belle for ${\Xi }_c^0\to {\Xi }^{-}{\ell }^{+}{\nu }_{\ell }$. In this work, we investigate the ${\Xi }_c\to \Xi$ form factors in QCD sum rules. To this end, the two-point correlation functions of ${\Xi }_c$ and $\Xi$, and the three-point correlation functions of ${\Xi }_c\to \Xi$ are calculated. At the QCD level, contributions from up to dimension-6 four-quark operators are considered, and the leading order results of the Wilson coefficients are obtained. For the form factors, relatively stable Borel windows can be found. Our form factors are comparable with those of Lattice QCD, except for $f_{\perp }$. The obtained form factors are then used to predict the branching ratios of ${\Xi }_c\to \Xi {\ell }^{+}{\nu }_{\ell }$, and our predictions are consistent with the most recent data of ALICE and Belle, and those of Lattice QCD within error. Given that the branching ratios only contain limited information, we suggest the experimentalists directly measure the form factors of ${\Xi }_c\to \Xi$.

   hep-phhep-exPRD(2023)·30 citations
3. 03*

   Operator product expansion for the non-local gluon condensate

   V. M. Braun🇩🇪 · K. G. Chetyrkin🇩🇪 · B. A. Kniehl🇩🇪

   We consider the short-distance expansion of the product of two gluon field strength tensors connected by a straight-line-ordered Wilson line. The vacuum expectation value of this nonlocal operator is a common object in studies of the QCD vacuum structure, whereas its nucleon expectation value is known as the gluon quasi-parton distribution and is receiving a lot of attention as a tool to extract gluon distribution functions from lattice calculations. Extending our previous study, we calculate the three-loop coefficient functions of the scalar operators in the operator product expansion up to dimension four. As a by-product, the three-loop anomalous dimension of the nonlocal two-gluon operator is obtained as well.

   hep-phJHEP(2021)·4 citations
4. 04*

   A radiatively induced inverse seesaw model with hidden $U(1)$ gauge symmetry

   Takaaki Nomura🇨🇳 · Hiroshi Okada🇰🇷 · Prasenjit Sanyal🇰🇷

   We propose an inverse seesaw scenario under hidden $U(1)$ gauge symmetry, having rather natural hierarchies among neutral fermion mass scales. The hierarchies are derived from theory and experimental constraints. The theory requires Majorana exotic masses have to be induced at one-loop level. The experimental side requests that the Dirac mass terms has to be highly suppressed to satisfy the constraints from the lepton flavor violations(LFVs) such as $\mu \to e\gamma$. In order to induce such a small Majorana exotic masses we introduce exotic fermions and bosons that also provide us additional intriguing phenomenologies such as muon anomalous magnetic moment, dark matter candidate as well as LFVs and deviations in leptonic $Z$ decays. We analyze these phenomenologies including neutrino oscillation data numerically, and show allowed region. Finally, we discuss the DM candidate in both the cases of fermion and scalar boson, where we focus on rather lighter range that is equal or less than 10 GeV. The dominant contributions originate from interactions of hidden gauge sector, and we show allowed ranges for both cases.

   hep-phEPJC(2022)·14 citations
5. 05*

   Hadronic Rescattering in pA and AA Collisions

   Christian Bierlich🇸🇪 · Torbjörn Sjöstrand🇸🇪 · Marius Utheim🇸🇪

   In a recent article we presented a model for hadronic rescattering, and some results were shown for pp collisions at LHC energies. In order to extend the studies to pA and AA collisions, the Angantyr model for heavy-ion collisions is taken as the starting point. Both these models are implemented within the general-purpose Monte Carlo event generator Pythia, which makes the matching reasonably straightforward, and allows for detailed studies of the full space--time evolution. The rescattering rate is significantly higher than in pp, especially for central AA collisions, where the typical primary hadron rescatters several times. We study the impact of rescattering on a number of distributions, such as pT and eta spectra, and the space--time evolution of the whole collision process. Notably rescattering is shown to give a significant contribution to elliptic flow in XeXe and PbPb, and to give a nontrivial impact on charm production.

   hep-phnucl-thEPJA(2021)·46 citations
6. 06*

   Scalar isoscalar mesons and the scalar glueball from radiative $J/\psi$ decays

   Andrey V. Sarantsev🇩🇪 · Igor Denisenko🇷🇺 · Ulrike Thoma🇩🇪 · Eberhard Klempt🇩🇪

   A coupled-channel analysis of BESIII data on radiative $J/\psi$ decays into $\pi \pi$, $K\bar{K}$, $\eta \eta$ and $\omega \varphi$ has been performed. The partial-wave amplitude is constrained by a large number of further data. The analysis finds ten isoscalar scalar mesons. Their masses, widths and decay modes are determined. The scalar mesons are interpreted as mainly SU(3)-singlet and mainly octet states. Octet isoscalar scalar states are observed with significant yields only in the 1500-2100\,MeV mass region. Singlet scalar mesons are produced over a wide mass range but their yield peaks in the same mass region. The peak is interpreted as scalar glueball. Its mass and width are determined to $M=1865$\er25${}_{-30}^{+10}$ {\rm MeV} and $\Gamma =370$\er$50_{-20}^{+30}$ {\rm MeV}, its yield in radiative $J/\psi$ decays to ($5.8\pm 1.0)10^{-3}$.

   hep-phPLB(2021)·93 citations
7. 07*

   Mass spectra of $N\Omega$ dibaryons in the ${}^3{S}_1$ and ${}^5{S}_2$ channels

   Xiao-Hui Chen🇨🇳 · Qi-Nan Wang🇨🇳 · Wei Chen🇨🇳 · Hua-Xing Chen🇨🇳

   We study the mass spectra of the $N\Omega$ dibaryons in the ${}^3{S}_1$ and ${}^5{S}_2$ channels with $J^P=1^{+}$ and $2^{+}$ respectively, by using the method of QCD sum rules. We construct two dibaryon interpolating currents in the molecular picture and calculate their correlation functions and spectral densities up to dimension-16 condensates. Our results indicate that there may exist an $N\Omega$ dibaryon bound state in the ${}^5{S}_2$ channel with a binding energy of about $21\mathrm{MeV}$. The masses of the ${}^3{S}_1$ $N\Omega$ dibaryons with $J^P=1^{+}$ are predicted to be higher than the $N\Omega$ and $\Lambda \Xi$ thresholds, and thus can decay into these final states directly in S-wave. The $N\Omega {(}^5{S}_2)$ dibaryon bound state can decay into the octet-octet final states $\Lambda \Xi$ and $\Sigma \Xi$ in D-wave via the quark rearrangement mechanism. The existence of these $N\Omega$ dibaryons may be identified in the relativistic heavy-ion collision experiments in the future.

   hep-phhep-exnucl-thPRD(2021)·15 citations
8. 08*

   TMDlib2 and TMDplotter: a platform for 3D hadron structure studies

   N.A. Abdulov🇷🇺 · A. Bacchetta🇮🇹 · S. Baranov🇷🇺 · A. Bermudez Martinez🇩🇪 · V. Bertone🇫🇷 · C. Bissolotti🇮🇹 · V. Candelise🇮🇹 · L.I. Estevez Banos🇩🇪 · M. Bury🇩🇪 · P.L.S. Connor🇩🇪 · L. Favart🇧🇪 · F. Guzman🇨🇺 and 26 other authors

   A common library, TMDlib2, for Transverse-Momentum-Dependent distributions (TMDs) and unintegrated parton distributions (uPDFs) is described, which allows for easy access of commonly used TMDs and uPDFs, providing a three-dimensional (3D) picture of the partonic structure of hadrons. The tool TMDplotter allows for web-based plotting of distributions implemented in TMDlib2, together with collinear pdfs as available in LHAPDF.

   hep-phnucl-exnucl-thEPJC(2021)·100 citations
9. 09*

   Probing mild-tempered neutralino dark matter through top-squark production at the LHC

   Monoranjan Guchait🇮🇳 · Arnab Roy🇮🇳 · Seema Sharma🇮🇳

   The lightest neutralino, assumed to be the lightest supersymmetric particle, is proposed to be a dark matter (DM) candidate for the mass $\mathcal{O}$(100) GeV. Constraints from various direct dark matter detection experiments and Planck measurements exclude a substantial region of parameter space of the minimal supersymmetric standard model (MSSM). However, a "mild-tempered" neutralino with dominant bino composition and a little admixture of Higgsino is found to be a viable candidate for DM. Within the MSSM framework, we revisit the allowed region of parameter space that is consistent with all existing constraints. Regions of parameters that are not sensitive to direct detection experiments, known as "blind spots," are also revisited. Complimentary to the direct detection of DM particles, a mild-tempered neutralino scenario is explored at the LHC with the center of mass energy $\sqrt{\mathrm{s}}$=13 TeV through the top-squark pair production, and its subsequent decays with the standard-model-like Higgs boson in the final state. Our considered channel is found to be very sensitive also to the blind spot scenario. Detectable signal sensitivities are achieved using the cut-based method for the high luminosity options $300$ and $3000\mathrm{f}{\mathrm{b}}^{-1}$, which are further improved by applying the multi-variate analysis technique.

   hep-phPRD(2021)·7 citations
10. 10*

    Global Electroweak Symmetric Vacuum

    Yang Bai🇺🇸 · Seung J. Lee🇰🇷 · Minho Son🇰🇷 · Fang Ye🇰🇷

    Although the Higgs potential in the Standard Model (SM) contains only a simple electroweak symmetry breaking vacuum in the small field region, additional metastable or global vacua could exist in models beyond the SM. In this paper, we study one intriguing scenario with an additional electroweak symmetric vacuum that could be the global one. For the thermal universe ending at the current metastable vacuum, the electroweak symmetry should stay non-restored at high temperatures. We realize the scenario in a model with Higgs-portal couplings to SM singlet scalars with approximately global O(N) symmetries with a large N. For a large portion of model parameter space, both the quantum and thermal tunneling rates are suppressed such that our current metastable vacuum is long-lived enough. Our scenario predicts order-one changes for the Higgs self-couplings and a large contribution to the signal of the off-shell Higgs invisible decay. It can be partly probed at the LHC Run 3 and well tested at the high luminosity LHC. We also discuss the subcritical (anti-de Sitter) bubbles from the thermal tunneling that could have a large population and interesting cosmological implications.

    hep-phhep-exJHEP(2021)·19 citations
11. 11*

    Accidentally Asymmetric Dark Matter

    Pouya Asadi🇺🇸 · Eric David Kramer🇮🇱 · Eric Kuflik🇮🇱 · Gregory W. Ridgway🇺🇸 · Tracy R. Slatyer🇺🇸 · Juri Smirnov🇺🇸

    We study the effect of a first-order phase transition in a confining $SU(N)$ dark sector with heavy dark quarks. The baryons of this sector are the dark matter candidate. During the confinement phase transition the heavy quarks are trapped inside isolated, contracting pockets of the deconfined phase, giving rise to a second stage of annihilation that dramatically suppresses the dark quark abundance. The surviving abundance is determined by the local accidental asymmetry in each pocket. The correct dark matter abundance is obtained for $\mathcal{O}(1-100)$ PeV dark quarks, above the usual unitarity bound.

    hep-phastro-ph.COPRL(2021)·59 citations
12. 12*

    Thermal Squeezeout of Dark Matter

    Pouya Asadi🇺🇸 · Eric David Kramer🇮🇱 · Eric Kuflik🇮🇱 · Gregory W. Ridgway🇺🇸 · Tracy R. Slatyer🇺🇸 · Juri Smirnov🇺🇸

    We carry out a detailed study of the confinement phase transition in a dark sector with a $SU(N)$ gauge group and a single generation of dark heavy quark. We focus on heavy enough quarks such that their abundance freezes out before the phase transition and the phase transition is of first-order. We find that during this phase transition the quarks are trapped inside contracting pockets of the deconfined phase and are compressed enough to interact at a significant rate, giving rise to a second stage of annihilation that can dramatically change the resulting dark matter abundance. As a result, the dark matter can be heavier than the often-quoted unitarity bound of $\sim 100$TeV. Our findings are almost completely independent of the details of the portal between the dark sector and the Standard Model. We comment briefly on possible signals of such a sector. Our main findings are summarized in a companion letter, while here we provide further details on different parts of the calculation.

    hep-phastro-ph.COPRD(2021)·90 citations
13. 13*

    On the transition form factors of the axial-vector resonance $f_1(1285)$ and its decay into $e^{+}{e}^{-}$

    Marvin Zanke🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪

    Estimating the contribution from axial-vector intermediate states to hadronic light-by-light scattering requires input on their transition form factors (TFFs). Due to the Landau-Yang theorem, any experiment sensitive to these TFFs needs to involve at least one virtual photon, which complicates their measurement. Phenomenologically, the situation is best for the $f_1(1285)$ resonance, for which information is available from $e^{+}{e}^{-}\to e^{+}{e}^{-}{f}_1$, $f_1\to 4\pi$, $f_1\to \rho \gamma$, $f_1\to \varphi \gamma$, and $f_1\to e^{+}{e}^{-}$. We provide a comprehensive analysis of the $f_1$ TFFs in the framework of vector meson dominance, including short-distance constraints, to determine to which extent the three independent TFFs can be constrained from the available experimental input, a prerequisite for improved calculations of the axial-vector contribution to hadronic light-by-light scattering. In particular, we focus on the process $f_1\to e^{+}{e}^{-}$, evidence for which has been reported recently by SND for the first time, and discuss the impact that future improved measurements will have on the determination of the $f_1$ TFFs.

    hep-phhep-exnucl-thJHEP(2021)·97 citations
14. 14*

    When FIMPs Decay into Neutrinos: The $N_{\mathrm{eff}}$ Story

    Alexey Boyarsky🇳🇱 · Maksym Ovchynnikov🇳🇱 · Nashwan Sabti🇬🇧 · Vsevolod Syvolap🇩🇰

    The existence of feebly interacting massive particles (FIMPs) could have significant implications on the effective number of relativistic species $N_{\mathrm{eff}}$ in the early Universe. In this work, we investigate in detail how short-lived FIMPs that can decay into neutrinos affect $N_{\mathrm{eff}}$ and highlight the relevant effects that govern its evolution. We show that even if unstable FIMPs inject most of their energy into neutrinos, they may still decrease $N_{\mathrm{eff}}$, and identify neutrino spectral distortions as the driving power behind this effect. As a case study, we consider Heavy Neutral Leptons (HNLs) and indicate which regions of their parameter space increase or decrease $N_{\mathrm{eff}}$. Moreover, we derive bounds on the HNL lifetime from the Cosmic Microwave Background and comment on the possible role that HNLs could play in alleviating the Hubble tension.

    hep-phastro-ph.COPRD(2021)·43 citations
15. 15*

    Systematic approach to $B$-physics anomalies and $t$-channel dark matter

    Giorgio Arcadi🇮🇹 · Lorenzo Calibbi🇨🇳 · Marco Fedele🇩🇪 · Federico Mescia🇪🇸

    We study renormalisable models with minimal field content that can provide a viable Dark Matter candidate through the standard freeze-out paradigm and, simultaneously, accommodate the observed anomalies in semileptonic $B$-meson decays at one loop. Following the hypothesis of minimality, this outcome can be achieved by extending the particle spectrum of the Standard Model either with one vector-like fermion and two scalars or two vector-like fermions and one scalar. The Dark Matter annihilations are mediated by $t$-channel exchange of other new particles contributing to the $B$-anomalies, thus resulting in a correlation between flavour observables and Dark Matter abundance. Again based on minimality, we assume the new states to couple only with left-handed muons and second and third generation quarks. Besides an ad hoc symmetry needed to stabilise the Dark Matter, the interactions of the new states are dictated only by gauge invariance. We present here for the first time a systematic classification of the possible models of this kind, according to the quantum numbers of the new fields under the Standard Model gauge group. Within this general setup we identify a group of representative models that we systematically study, applying the most updated constraints from flavour observables, dedicated Dark Matter experiments, and LHC searches of leptons and/or jets and missing energy, and of disappearing charged tracks.

    hep-phhep-exPRD(2021)·26 citations
16. 16*

    First Principles Prediction of the Landau Parameter for Fermi Liquids near the Unitarity Limit

    Shashin Pavaskar🇺🇸 · Ira Z. Rothstein🇺🇸

    This paper explores the behavior of systems of cold fermions as they approach unitarity above the critical temperature. As we move away from unitarity, by decreasing the scattering length, the dilaton, the Goldstone boson resulting from the spontaneous breaking of Schrodinger symmetry by the Fermi sea, becomes gapped. At energies below this gap, the interaction between quasi-particles will be dominated by local interactions generated by off-shell dilaton exchange. The dilaton mass can, in turn, be related via anomaly matching, to the scattering length and contact parameter within the confines of a systematic expansion. We use this relation to predict the s-wave Landau parameter to be $f=\frac{4\pi a(2ϵ(p_F)-p_F^2/m_{\star }{)}^{2}m}{3p_F^4\tilde{C}(a)}$ where $a$ is the scattering length, $m$ the atomic mass, $m_{\star }$, the effective mass which can be extracted from heat capacity, and $\tilde{C}(a)$ is the dimensionless contact parameter. The range of validity of this prediction (given in eq.(21)) is determined by the value of contact parameter and Fermi velocity, which depend upon the scattering length. It is expected to be valid in a range above $k_{F}a\sim 1$, but the actual window will depend upon the values of aforementioned parameters. Given this result for $f$, we predict the compressibility, spin susceptibility and the quasi-particle life-time.

    ↳ cond-mat.quant-gashep-phhep-thnucl-thPRB(2022)·6 citations
17. 17*

    Hidden Parameters in Heisenberg's and Landau-Peierls Uncertainty Relations, Speed of Virtual Particles and Space-Time Metric Types

    B. B. Levchenko🇷🇺

    In quantum field theory, virtual particles are carriers of relativistic wave fields, participate in vacuum fluctuations, and are a consequence of the implementation of the quantum uncertainty mechanism. Virtual particles, playing a fundamental role in our understanding and description of interaction processes, are themselves inaccessible to direct observation and measurement of their dynamic characteristics. We prove that the well-known Heisenberg uncertainty relations and Landau-Peierls uncertainty relations implicitly contain new "hidden" angular variables. On the basis of the relations obtained, we derive a formula for estimating the speed $u$ of a virtual particle in indirect measurements. This formula is applicable in cases where the final state is characterized by an incomplete set of variables. Moreover, we present arguments that the speed of a virtual particle is a sensitive indicator of non-linearity of the process dynamics and propose a method for revealing the type of space-time geometry in the interaction region of high-energy particles.

    ↳ quant-phhep-exhep-ph0 citations
18. 18*

    Parton physics from a heavy-quark operator product expansion: Formalism and Wilson coefficients

    William Detmold🇺🇸 · Anthony V. Grebe🇺🇸 · Issaku Kanamori🇯🇵 · C.-J. David Lin🇹🇼 · Robert J. Perry🇹🇼 · Yong Zhao🇺🇸

    Parton distribution functions (PDFs) and light-cone distribution amplitudes (LCDAs) are central non-perturbative objects of interest in high-energy inelastic and elastic scattering, respectively. As a result, an ab-initio determination of these objects is highly desirable. In this paper we present theoretical details for the calculation of the PDFs and LCDAs using a heavy-quark operator product expansion method. This strategy was proposed in a previous paper [Phys. Rev. D 73, 014501 (2006)] for computing higher moments of the PDFs using lattice QCD. Its central feature is the introduction of a fictitious, valence heavy quark. In the current article, we show that the operator product expansion (OPE) of the hadronic matrix element we study can also be expressed as the convolution of a perturbative matching kernel and the corresponding light-cone distribution, which in principle can be inverted to determine the parton momentum fraction dependence. Regarding the extraction of higher moments, this work also provides the one-loop Wilson coefficients in the OPE formulas for the unpolarized PDF, helicity PDF and pseudo-scalar meson LCDAs. Although these Wilson coefficients for the PDFs can be inferred from existing results in the literature, those for the LCDAs are new.

    ↳ hep-lathep-phnucl-thPRD(2021)·54 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.