Tue·Jul 14, 2020Tuesday·July 14, 2020

1. 01*

   The pion light-cone distribution amplitude from the pion electromagnetic form factor

   Shan Cheng🇨🇳 · Alexander Khodjamirian🇩🇪 · Aleksey V. Rusov🇬🇧

   We suggest to probe the pion light-cone distribution amplitude, applying a dispersion relation for the pion electromagnetic form factor. Instead of the standard dispersion relation, we use the equation between the spacelike form factor $F_{\pi }(Q^2)$ and the integrated modulus of the timelike form factor. For $F_{\pi }(Q^2)$, the QCD light-cone sum rule with a dominant twist-2 term is used. Adopting for the pion twist-2 distribution amplitude a certain combination of the first few Gegenbauer polynomials, it is possible to fit their coefficients $a_{2,4,6,...}$ (Gegenbauer moments) from this equation, employing the measured pion timelike form factor. For the exploratory fit we use the data of the BaBar collaboration. The results definitely exclude the asymptotic twist-2 distribution amplitude. Also the model with a single $a_2\ne 0$ is disfavoured by the fit. Considering the models with $a_{n>2}\ne 0$, we find that the fitted values of the second and fourth Gegenbauer moments cover the intervals $a_2(1\text{mbox}GeV)=(0.22-0.33)$, $a_4(1\text{mbox}GeV)=(0.12-0.25)$. The higher moments starting from $a_8$ are consistent with zero, albeit with large uncertainties. The spacelike pion form factor obtained in two different ways, from the dispersion relation and from the light-cone sum rule, agrees, within uncertainties, with the measurement by the Jefferson Lab $F_{\pi }$ collaboration.

   hep-phPRD(2020)·41 citations
2. 02*

   Infrared-suppressed QCD coupling and the hadronic contribution to muon g-2

   Gorazd Cvetic🇨🇱 · Reinhart Kogerler🇩🇪

   A variant of QCD with the coupling suppressed in the infrared (IR) regime, as suggested by large-volume lattice calculations of the Landau-gauge gluon and ghost dressing functions, is considered. The coupling is further restricted by the condition of approximate coincidence with perturbative QCD in the high momentum regime, and by the $\tau$-lepton semihadronic decay rate in the intermediate momentum regime, the rate which is evaluated by a renormalon-motivated resummation method. The obtained coupling turns out to be free of Landau singularities. The $D=4,6$ condensate values of the Adler function are then extracted by application of the Borel sum rules to the OPAL and ALEPH (V+A)-channel data of $\tau$-decay, and the corresponding V-channel condensate values are deduced as well. We then show that the correct value of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment, $a_{\mu }^{\mathrm{had}(1)}$, is reproduced by regularizing the $D=4,6$ OPE terms in the V-channel Adler function with IR-regularization masses ${\mathcal{M}}_{D/2}\lesssim 1\mathrm{GeV}$, suggesting the internal consistency of the presented QCD framework.

   hep-phJ.Phys.G(2020)·12 citations
3. 03*

   Magnetic effects of QCD parameters from finite energy sum rules

   Cristian Villavicencio🇨🇱 · C. A. Dominguez🇿🇦 · M. Loewe🇨🇱

   One of the advantages of the finite energy sum rules is the fact that every operator in the operator product expansion series can be selected individually by the use of an appropriate kernel function which removes other operator poles. This characteristic is maintained by QCD systems in the presence of external homogeneous magnetic field, providing interesting information about the magnetic evolution of QCD and hadronic parameters. In this work finite energy sum rules are applied on QCD in the light quark sector, combining axial and pseudoscalar channels in the presence of an external homogeneous magnetic field, obtaining the magnetic evolution of the light quark masses, pion mass, the pion decay constant, the gluon condensate and the continuum hadronic threshold.

   hep-phnucl-thJ.Phys.Conf.Ser.(2020)·3 citations
4. 04*

   Flavored axions and the flavor problem

   Yithsbey Giraldo🇨🇴 · R. Martinez🇨🇴 · Eduardo Rojas🇨🇴 · Juan C. Salazar🇨🇴

   A Peccei-Quinn~(PQ) symmetry is proposed in order to generate in the Standard Model~(SM) quark sector a realistic mass matrix ansatz with five texture-zeros. Limiting our analysis to Hermitian mass matrices, we show that this requires a minimum of 4 Higgs doublets. This model allows assigning values close to 1 for several Yukawa couplings, giving insight into the origin of the mass scales in the SM. Since the PQ charges are non-universal, the model features Flavor-Changing Neutral Currents~(FCNC) at the tree level. From the analytical expressions for the FCNC we report the allowed region in the parameter space obtained from the measurements of branching ratios of semileptonic meson decays.

   hep-phEPJC(2022)·7 citations
5. 05*

   Charm fragmentation functions in the Nambu-Jona-Lasinio model

   Dong-Jing Yang🇹🇼 · Hsiang-nan Li🇹🇼

   We derive the fragmentation function (FF), which describes the probability for a charm quark to emit a $D$ meson with a certain momentum fraction, in the Nambu-Jona-Lasinio (NJL) model. The corresponding elementary FF is calculated with the quark-meson coupling determined in the NJL model involving charm quarks. The FF in the infinite momentum frame is constructed through the jet process governed by the elementary FF, and then evolved to the charm scale, at which it is defined. To prepare the FF suitable for an analysis of $D$ meson production at CLEO, we further match the above FF to that in the finite momentum frame at one loop in QCD. It is shown that the charm quark FF including the finite momentum effects leads to theoretical results in agreement with the CLEO data.

   hep-phPRD(2020)·2 citations
6. 06*

   Vacuum and thermal fluctuation energies of a soliton at finite temperatures

   Song Shu🇨🇳 · Xiaogang Li🇨🇳 · Jia-Rong Li🇨🇳

   We have studied the vacuum and thermal fluctuation energies of a soliton at finite temperatures. First the vacuum energy coming from the Dirac sea is calculated by a summation of the discrete and continuum energy spectrum of the Dirac equation in the background field of a soliton. And all the divergences are removed by the same renormalization scheme at zero temperature. Then the vacuum energy and thermal fluctuation energy at finite temperatures in a temperature dependent soliton background are calculated. And the numerical results are analyzed and discussed.

   hep-phnucl-thNPA(2021)·2 citations
7. 07*

   Momentum dependence of light nuclei production in pp, p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider

   Rui-Qin Wang🇨🇳 · Feng-Lan Shao🇨🇳 · Jun Song🇨🇳

   We study the momentum dependence of the production of light nuclei in high energy collisions in the nucleon coalescence/recombination mechanism. We derive formulas of the momentum distributions of deuterons ($d$) and helions (${}^3$He). We obtain the analytic expressions of the coalescence factor $B_A$'s ($B_2$ for $d$ and $B_3$ for ${}^3$He) as functions of the collision system size and the momentum. We apply the deduced results to p-p, p-Pb and Pb-Pb collisions to naturally explain the interesting behaviors of $B_A$ observed in experiments at the CERN Large Hadron Collider.

   hep-phhep-exnucl-thPRC(2021)·13 citations
8. 08*

   A Natural Scotogenic Model for Neutrino Mass \& Dark Matter

   Amine Ahriche (Sharjah U., ICTP, Trieste & ENS-Kouba, Algiers)🇮🇹 · Adil Jueid (Konkuk U., Seoul)🇰🇷 · Salah Nasri (United Arab Emirates U. & ICTP, Trieste)🇦🇪

   In this letter, we propose an extension of the scotogenic model where singlet Majorana particle can be dark matter (DM) without the need of a highly suppressed scalar coupling of the order $O(10^{-10})$. For that, the SM is extended with three singlet Majorana fermions, an inert scalar doublet, and two (a complex and a real) singlet scalars, with a global $Z_4$ symmetry that is spontaneously broken into $Z_2$ at a scale higher than the electroweak one by the vev of the complex singlet scalar. In this setup, the smallness of neutrino mass is achieved via the cancellation between three diagrams a la scotogenic, a DM candidate that is viable for a large mass range; and the phenomenology is richer than the minimal scotogenic model.

   hep-phPLB(2021)·18 citations
9. 09*

   Pion-nucleus induced Drell-Yan cross section in models inspired by light-front holography

   Jiangshan Lan🇨🇳 · Chandan Mondal🇨🇳

   We evaluate the cross section for the pion induced Drell-Yan process in two different models of the pion light-front wave function, inspired by light-front holographic approaches. We obtain the valence quark distribution functions in those models, which after QCD evolution, are consistent with the experimental data from the E-0615 experiment at Fermilab. Supplemented by the parton distribution functions of the target nuclei, we obtain the cross section consistent with the experimental data for the ${\pi }^{-}$ Nucleus $\to {\mu }^{+}{\mu }^{-}X$ Drell-Yan process.

   hep-phPLB(2020)·4 citations
10. 10*

    A modified version of the Koide formula from flavor nonets in a scalar potential model and in a Yukawaon model

    Zhengchen Liang🇨🇳 · Zheng Sun🇨🇳

    We present a modified version of the Koide formula from a scalar potential model or from a Yukawaon model, based on scalar fields set up in a nonet representation of the SU(3) flavor symmetry in the Standard Model. The Koide's character, which involves the Standard Model fermion mass ratios, is derived from the vacuum expectation value of the nonet field in either model. The scalar potential in the scalar potential model or the superpotential in the Yukawaon model is constructed with all terms invariant under symmetries. The resulting Koide's character, which is modified by two effective parameters, can fit the experimental mass data of charged leptons, up quarks and down quarks. It offers a natural interpretation of the Standard Model fermion mass spectrum.

    hep-phhep-thNPB(2021)·1 citation
11. 11*

    Dirac neutrino mass models with a modular $S_4^{}$ symmetry

    Xin Wang🇨🇳

    In this paper, we investigate lepton mass spectra, flavor mixing and CP violation with a modular $S_4^{}$ symmetry under the assumption that neutrinos are Dirac fermions. We find that the Majorana mass term can be forbidden by adjusting the weight of the right-handed neutrino superfields. We study the scenarios where modular forms in the neutrino sector take the lowest non-trivial weight two, while those in the charged-lepton sector vary from two to six. The corrections from renormalization-group running effects to our model have also been discussed in detail. We totally obtain twelve different classes of models and find that ten of them can accommodate current neutrino oscillation data.

    hep-phNPB(2021)·50 citations
12. 12*

    On the LHC signatures of $SU(5)\times U(1{)}^{\prime }$ F-theory motivated models

    A. Karozas🇬🇷 · G. K. Leontaris🇬🇷 · I. Tavellaris🇬🇷 · N. D. Vlachos🇬🇷

    We study low energy implications of F-theory GUT models based on $SU(5)$ extended by a $U(1{)}^{\prime }$ symmetry which couples non-universally to the three families of quarks and leptons. This gauge group arises naturally from the maximal exceptional gauge symmetry of an elliptically fibred internal space, at a single point of enhancement, $E_8\supset SU(5)\times SU(5{)}^{\prime }\supset SU(5)\times U(1{)}^4$. Rank-one fermion mass textures and a tree-level top quark coupling are guaranteed by imposing a $Z_2$ monodromy group which identifies two abelian factors of the above breaking sequence. The $U(1{)}^{\prime }$ factor of the gauge symmetry is an anomaly free linear combination of the three remaining abelian symmetries left over by $Z_2$. Several classes of models are obtained, distinguished with respect to the $U(1{)}^{\prime }$ charges of the representations, and possible extra zero modes coming in vector-like representations. The predictions of these models are investigated and are compared with the LHC results and other related experiments. Particular cases interpreting the B-meson anomalies observed in LHCb and BaBar experiments are also discussed.

    hep-phhep-exhep-thEPJC(2021)·12 citations
13. 13*

    SUSY-Breaking Scenarios With a Mildly Violated R Symmetry

    C. Pallis🇬🇷

    New realizations of the gravity-mediated SUSY breaking are presented consistently with an R symmetry. We employ monomial superpotential terms for the hidden-sector (goldstino) superfield and Kahler potentials parameterizing compact or non-compact Kahler manifolds. Their scalar curvature may be systematically related to the R charge of the goldstino so that Minkowski solutions without fine tuning are achieved. A mild violation of the R symmetry by a higher order term in the Kahler potentials allows for phenomenologically acceptable masses for the R axion. In all cases, non-vanishing soft SUSY-breaking parameters are obtained and a solution to the mu problem of MSSM may be accommodated by conveniently applying the Giudice-Masiero mechanism.

    hep-phhep-thEPJC(2021)·11 citations
14. 14*

    Resonances $\varphi (1020)$ and $\varphi (1680)$ contributions for the three-body decays $B^{+}\to D_s^{+}K\bar{K}$

    Ai-Jun Ma🇨🇳

    We study the resonances $\varphi (1020)$ and $\varphi (1680)$ contributions for the three-body decays $B^{+}\to D_s^{+}K\bar{K}$ in the perturbative QCD approach. The branching ratios for $B^{+}\to D_s^{+}\varphi (1020)\to D_s^{+}{K}^{+}{K}^{-}$ and $B^{+}\to D_s^{+}\varphi (1020)\to D_s^{+}{K}^0{\bar{K}}^0$ are predicted to be $(1.53\pm 0.23)\times 10^{-7}$ and $(1.02_{-0.13}^{+0.19})\times 10^{-7}$, respectively. The decay $B^{+}\to D_s^{+}\varphi (1680)$ with $\varphi (1680)$ decays into $K^{+}{K}^{-}$ or $K^0{\bar{K}}^0$, has the branching fraction $(6.94_{-2.02}^{+1.83})\times 10^{-9}$, which is about $5\%$ of the result for $B^{+}\to D_s^{+}\varphi (1020)\to D_s^{+}{K}^{+}{K}^{-}$.

    hep-phInt.J.Mod.Phys.A(2020)·4 citations
15. 15*

    Hidden and open heavy-flavor hadronic states

    H. Garcilazo🇲🇽 · A. Valcarce🇪🇸

    We discuss the stability of hidden and open heavy-flavor hadronic states made of either two or three mesons. References are made in passing to studies regarding two and three-body systems containing baryons. We perform a comparative study analyzing the results in terms of quark and hadron degrees of freedom. Compact and molecular states are found to exist in very specific situations. We estimate the decay width for the different scenarios: weak decays for bound states by the strong interaction, and strong decays for hadronic resonances above a decay threshold. The experimental observation of narrow hadrons lying well above their lowest decay threshold is theoretically justified.

    hep-phnucl-thFew Body Syst.(2020)·6 citations
16. 16*

    CP Violation in $B$ Decays (and the Search for New Physics)

    David London🇨🇦

    In this talk, I review the various measurements that have been made over the years of CP-violating observables in $B$ decays. These include indirect CP asymmetries, direct CP asymmetries, and triple products. All are discussed in the context of the search for new physics (NP). The only hints of NP have appeared in (i) $B\to \pi K$ decays and (ii) 3-body $B\to K\pi \pi$ and $B\to K\bar{K}K$ decays, where the extracted (loop-level) value of $\gamma$ may differ from the value found using (tree-level) $B^{+}\to D^{(\ast )}{K}^{(\ast )+}$ decays. CP-violating observables may also be used to distinguish among the models proposed to explain the current anomalies observed in $b\to s{\mu }^{+}{\mu }^{-}$ and $b\to c\tau {\bar{\nu }}_{\tau }$ decays.

    hep-ph1 citation
17. 17*

    Non-linear equation in the re-summed next-to-leading order of perturbative QCD: the leading twist approximation

    Carlos Contreras (UTFSM)🇨🇱 · Eugene Levin (Tel Aviv U./UTFSM)🇮🇱 · Rodrigo Meneses (U. de Valparaiso)🇨🇱 · Michael Sanhueza (UTFSM)🇨🇱

    In this paper, we use the re-summation procedure, suggested in Refs.\cite{DIMST,SALAM,SALAM1,SALAM2}, to fix the BFKL kernel in the NLO. However, we suggest a different way to introduce th non-linear corrections in the saturation region, which is based on the leading twist non-linear equation. In the kinematic region:$\tau \equiv r^2{Q}_s^2(Y)\le 1$ , where $r$ denotes the size of the dipole, $Y$ its rapidity and $Q_s$ the saturation scale, we found that the re-summation contributes mostly to the leading twist of the BFKL equation. Assuming that the scattering amplitude is small, we suggest using the linear evolution equation in this region. For $\tau >1$ we are dealing with the re-summation of $\text{Lb}\text{bas}\ln \tau {\text{Rb}}^n$ and other corrections in NLO approximation for the leading twist.We find the BFKL kernel in this kinematic region and write the non-linear equation, which we solve analytically. We believe the new equation could be a basis for a consistent phenomenology based on the CGC approach.

    hep-phEPJC(2020)·9 citations
18. 18*

    Survey of Texture Zeros with Light Dirac Neutrinos

    Happy Borgohain🇮🇳 · Debasish Borah🇮🇳

    We classify all possible texture zeros in light neutrino mass matrix in diagonal charged lepton basis by considering Dirac nature of light neutrinos. For Hermitian nature of neutrino mass matrix, the number of possible texture zeros remain same as Majorana texture zeros, but with less free parameters due to the absence of additional Majorana CP phases. Relaxing the Hermitian nature of neutrino mass matrix lead to many more possibilities and freedom due to additional CP phases, mixing angles not constrained by neutrino data. While we find that none of the texture zeros in Hermitian case are allowed, in non-Hermitian case some textures even with four zeros are allowed. While most of the one-zero, two-zero and three-zero textures in this case are allowed, four-zero textures are tightly constrained with only 6 allowed out of 126 possibilities. The allowed textures also give interesting correlations between light neutrino parameters with sharp distinctions between normal and inverted mass ordering. Many of these allowed textures also saturate the Planck 2018 upper bound on the sum of absolute neutrino masses.

    hep-phJ.Phys.G(2021)·23 citations
19. 19*

    On direct search for dark matter in scattering processes within Yukawa model

    V. Skalozub🇺🇦 · M. Dmytriiev🇺🇦

    \begin{abstract} Nowadays, no dark matter candidates have been discovered. We consider two possible reasons for that, both related to the approach of on-peak resonance searching for. As is believed usually, a new particle suits the conditions that the ratio of the width to the mass is less than $1-3\%$ and a narrow width approximation (NWA) is applicable to identify the such type resonant peak in the invariant mass spectrum of collision products. In the present paper, in the framework of generalized Yukawa model, we find out the properties of the searched particle when its width is larger than a maximal one expected during experiments and so this state could be missed as a noise. We also ascertain the values of particle's parameters when the NWA is not applicable and estimate the width value when it happens. These estimations are relevant to interactions between the Standard model and dark matter particles. Such approach is focused on the role of couplings and mass values introduced in the model describing interaction of visible and dark matter. Key words: dark matter; resonance; narrow width approximation; mixing of fields.

    hep-phUkr.J.Phys.(2021)·2 citations
20. 20*

    Thermodynamic properties of interacting bosons with zero chemical potential

    O. S. Stashko🇺🇦 · D. V. Anchishkin🇺🇦 · O. V. Savchuk🇺🇦 · M. I. Gorenstein🇺🇦

    Thermodynamics properties of an interacting system of bosons are considered at finite temperatures and zero chemical potential within the Skyrme-like mean-field model. An interplay between attractive and repulsive interactions is investigated. As a particular example an equilibrium system of pions is discussed. Several modifications of thermodynamic properties in the considered system are found with increasing a strength of attractive forces. Different types of the first order phase transition are classified. Some of these transitions exist also in the Boltzmann approximation. However, effects of the Bose statistics introduce the notable additional changes in the thermodynamic quantities due to a possibility of the Bose-Einstein condensation.

    hep-phnucl-thJ.Phys.G(2021)·8 citations
21. 21*

    Two-loop coefficient function for DVCS: Vector contributions

    V. M. Braun🇩🇪 · A. N. Manashov🇩🇪 · S. Moch🇩🇪 · J. Schoenleber🇩🇪

    Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the vector flavor-nonsinglet contribution to deeply-virtual Compton scattering (DVCS). The analytic expression for the coefficient function in momentum fraction space is presented in the $\overline{\text{MS}}$ scheme. The corresponding next-to-next-to-leading order correction to the Compton form factor $\mathcal{H}$ for a simple model of the generalized parton distribution appears to be rather large: a factor two smaller than the next-to-leading order correction, approximately $\sim 10$\% of the tree level result in the bulk of the kinematic range, for $Q^2=4$ GeV${}^2$.

    hep-phJHEP(2020)·42 citations
22. 22*

    Evidence of a simple dark sector from XENON1T excess

    Cheng-Wei Chiang🇹🇼 · Bo-Qiang Lu🇹🇼

    We propose that the nearly massless dark photons produced from the annihilation of keV dark fermions in the Galaxy can induce the excess of electron recoil events recently observed in the XENON1T experiment. The minimal model for this is the extension of a $U(1{)}_X$ gauge symmetry, under which the dark photon couples to both dark and visible matter currents. We find that the best-fit parameters of the dark sector are compatible with the most stringent constraints from stellar cooling. We also show that in the freeze-out scenario, the dark fermions can explain the anomaly while contributing $\gtrsim 1\%$ of the DM relic density.

    hep-phastro-ph.HEPRD(2020)·26 citations
23. 23*

    The $\sigma$-meson: four-quark vs. two-quark components and decay width in a Bethe-Salpeter approach

    Nico Santowsky🇩🇪 · Gernot Eichmann🇵🇹 · Christian S. Fischer🇩🇪 · Paul C. Wallbott🇩🇪 · Richard Williams🇩🇪

    We study the dynamical generation of resonances in isospin singlet channels with mixing between two- and four-quark states. To this end we generalise a Bethe-Salpeter approach to four-quark states employed previously \cite{Heupel:2012ua} to accommodate for mixing diagrams. The $q\bar{q}q\bar{q}$ and $q\bar{q}$ components of the Bethe-Salpeter wave function (with light quarks $q\in \{u,d\}$) are determined consistently in a symmetry-preserving truncation of the underlying Dyson-Schwinger equations. As a prominent example we deal with the isospin-singlet $0^{++}$ meson with light quark content. We find that the $\pi \pi$ contribution of the four-quark component is mainly responsible for the low (real part of the) mass of the resulting state. We also study the analytic structure in the complex momentum plane and find a branch cut at the two-pion threshold and a singularity in the second Riemann sheet indicating a considerable decay width. Our findings are in excellent qualitative agreement with the general picture for the $\sigma /f_0(500)$ that emerged in the past two decades from dispersive approaches \cite{Pelaez:2015qba}.

    hep-phPRD(2020)·42 citations
24. 24*

    NNLO QCD$\times$EW corrections to on-shell $Z$ production

    Roberto Bonciani🇮🇹 · Federico Buccioni🇬🇧 · Narayan Rana🇮🇹 · Alessandro Vicini🇮🇹

    We present the first analytical results for the $\mathcal{O}(\alpha {\alpha }_s)$ corrections to the total cross section for the inclusive production of an on-shell $Z$ boson at hadron colliders. We include the complete set of contributions, with photonic and massive weak gauge boson effects, which have been computed in analytical form and expressed in terms of polylogarithmic and elliptic integrals. We present numerical results, relevant for the precision studies at the LHC. These corrections increase the accuracy of the predictions and contribute to the reduction of the QCD component of the theoretical uncertainty.

    hep-phhep-exPRL(2020)·57 citations
25. 25*

    Split Higgs triplet

    Pei-Hong Gu🇨🇳

    We find if a Higgs triplet with hypercharge has a special dimension-6 operator with the standard model Higgs doublet, i.e. a square of the trilinear triplet-doublet coupling, its scalar(pseudo-scalar) component can obtain a small quadratic term while its pseudo-scalar(scalar) and charged-scalar components can hold their masses heavy enough. Such split Higgs triplet can spontaneously develop a small vacuum expectation value to realize a Majorana neutrino mass generation without causing any high-dimensional lepton number violations including the well-known Weinberg dimension-5 operator. Alternatively it can mediate a non-standard neutrino self-interaction motivated by resolving the tension in Hubble constant measurements. This effective theory with rich observable phenomena can be induced by the Georgi-Machacek Higgs triplets at tree level or some dark matter fields at one-loop order.

    hep-ph0 citations
26. 26*

    Energy-Momentum portal to dark matter and emergent gravity

    Pascal Anastasopoulos🇦🇹 · Kunio Kaneta🇺🇸 · Yann Mambrini🇫🇷 · Mathias Pierre🇪🇸

    We propose a new scenario where dark matter belongs to a secluded sector coupled to the Standard Model through energy--momentum tensors. Our model is motivated by constructions where gravity {\it emerges} from a hidden sector, the graviton being identified by the kinetic term of the fields in the secluded sector. Supposing that the lighter particle of the secluded sector is the dark component of the Universe, we show that we can produce it in a sufficiently large amount despite the suppressed couplings of the theory, thanks to large temperatures of the thermal bath in the early stage of the Universe.

    hep-phastro-ph.COhep-thPRD(2020)·24 citations
27. 27*

    Calculating the primary Lund Jet Plane density

    Andrew Lifson🇸🇪 · Gavin P. Salam🇬🇧 · Gregory Soyez🇫🇷

    The Lund-jet plane has recently been proposed as a powerful jet substructure tool with a broad range of applications. In this paper, we provide an all-order single logarithmic calculation of the primary Lund-plane density in Quantum Chromodynamics, including contributions from the running of the coupling, collinear effects for the leading parton, and soft logarithms that account for large-angle and clustering effects. We also identify a new source of clustering logarithms close to the boundary of the jet, deferring their resummation to future work. We then match our all-order results to exact next-to-leading order predictions. For phenomenological applications, we supplement our perturbative calculation with a Monte Carlo estimate of non-perturbative corrections. The precision of our final predictions for the Lund-plane density is 5-7% at high transverse momenta, worsening to about 20% at the lower edge of the perturbative region, corresponding to transverse momenta of about 5 GeV. We compare our results to a recent measurement by the ATLAS collaboration at the Large-Hadron Collider, revealing good agreement across the perturbative domain, i.e. down to about 5 GeV.

    hep-phhep-exJHEP(2020)·66 citations
28. 28*

    Cosmic Imprints of XENON1T Axions

    Fernando Arias-Aragon🇪🇸 · Francesco D'Eramo🇮🇹 · Ricardo Z. Ferreira🇸🇪 · Luca Merlo🇪🇸 · Alessio Notari🇪🇸

    The recent electron recoil excess observed by XENON1T has a possible interpretation in terms of solar axions coupled to electrons. If such axions are still relativistic at recombination they would also leave a cosmic imprint in the form of an additional radiation component, parameterized by an effective neutrino number $\Delta N_{\text{eff}}$. We explore minimal scenarios with a detectable signal in future CMB surveys: axions coupled democratically to all fermions, axion-electron coupling generated radiatively, the DFSZ framework for the QCD axion. The predicted $\Delta N_{\text{eff}}$ is larger than $0.03-0.04$ for all cases, close to the $2\sigma$ forecasted sensitivity of CMB-S4 experiments. This opens the possibility of testing with cosmological observations the solar axion interpretation of the XENON1T excess.

    hep-phastro-ph.COJCAP(2020)·56 citations
29. 29*

    Relations between $b\to c\tau \nu$ Decay Modes in Scalar Models

    Stefan Schacht🇺🇸 · Amarjit Soni🇺🇸

    As a consequence of the Ward identity for hadronic matrix elements, we find relations between the differential decay rates of semileptonic decay modes with the underlying quark-level transition $b\to c\tau \nu$, which are valid in scalar models. The decay-mode dependent scalar form factor is the only necessary theoretical ingredient for the relations. Otherwise, they combine measurable decay rates as a function of the invariant mass-squared of the lepton pair $q^2$ in such a way that a universal decay-mode independent function is found for decays to vector and pseudoscalar mesons, respectively. This can be applied to the decays $B\to D^{\ast }\tau \nu$, $B_s\to D_s^{\ast }\tau \nu$, $B_c\to J/\psi \tau \nu$ and $B\to D\tau \nu$, $B_s\to D_s\tau \nu$, $B_c\to {\eta }_c\tau \nu$, with implications for $R(D^{(\ast )})$, $R(D_s^{(\ast )})$, $R(J/\psi )$, $R({\eta }_c)$, and $\mathcal{B}(B_c\to \tau \nu )$. The slope and curvature of the characteristic $q^2$-dependence is proportional to scalar new physics parameters, facilitating their straight forward extraction, complementary to global fits.

    hep-phhep-exhep-latJHEP(2020)·6 citations
30. 30*

    Exact Theory of Non-relativistic Quadrupole Bremsstrahlung

    Josef Pradler🇦🇹 · Lukas Semmelrock🇦🇹

    The quantum mechanical treatment of quadrupole radiation due to bremsstrahlung exact to all orders in the Coulomb interaction of two non-relativistically colliding charged spin-0 and unpolarized spin-1/2 particles is presented. We calculate the elements of the quadrupole tensor, and present analytical solutions for the double differential photon emission cross section of identical and non-identical particles. Contact is made to Born-level and quasi-classical results in the respective kinematic limits and effective energy loss rates are obtained. A generally valid formula for soft-photon emission is established and an approximate formula across the entire kinematic regime is constructed. The results apply to bremsstrahlung emission in the scattering of pairs of electrons and are hence relevant in the study of astrophysical phenomena. A definition of a Gaunt factor is proposed which should facilitate broad applicability of the results.

    hep-phApJ(2021)·9 citations
31. 31*

    Electric conductivity in finite-density SU(2) lattice gauge theory with dynamical fermions

    P. V. Buividovich🇬🇧 · D. Smith🇩🇪 · L. von Smekal🇩🇪

    We study the dependence of the electric conductivity on chemical potential in finite-density $SU(2)$ gauge theory with $N_f=2$ flavours of rooted staggered sea quarks, in combination with Wilson-Dirac and Domain Wall valence quarks. The pion mass is reasonably small with $m_{\pi }/m_{\rho }\approx 0.4$. We concentrate in particular on the vicinity of the chiral crossover, where we find the low-frequency electric conductivity to be most sensitive to small changes in fermion density. Working in the low-density QCD-like regime with spontaneously broken chiral symmetry, we obtain an estimate of the first nontrivial coefficient $c(T)$ of the expansion of conductivity $\sigma (T,\mu )=\sigma (T,0)\left(1+c(T)(\mu /T{)}^2+O({\mu }^4)\right)$ in powers of $\mu$, which has rather weak temperature dependence and takes its maximal value $c(T)\approx 0.10\pm 0.07$ around the critical temperature. At larger densities and lower temperatures, the conductivity quickly grows towards the diquark condensation phase, and also becomes closer to the free quark result. As a by-product of our study we confirm the conclusions of previous studies with heavier pion that for $SU(2)$ gauge theory the ratio of crossover temperature to pion mass $T_c/m_{\pi }\approx 0.4$ at $\mu =0$ is significantly smaller than in real QCD.

    ↳ hep-lathep-phhep-thPRD(2020)·36 citations
32. 32*

    Lorentz and permutation invariants of particles II

    Ben Gripaios🇬🇧 · Ward Haddadin🇬🇧 · C. G. Lester🇬🇧

    Two theorems of Weyl tell us that the algebra of Lorentz- (and parity-) invariant polynomials in the momenta of $n$ particles are generated by the dot products and that the redundancies which arise when $n$ exceeds the spacetime dimension $d$ are generated by the $(d+1)$-minors of the $n\times n$ matrix of dot products. Here, we use the Cohen-Macaulay structure of the invariant algebra to provide a more direct characterisation in terms of a Hironaka decomposition. Among the benefits of this approach is that it can be generalized straightforwardly to cases where a permutation group acts on the particles, such as when some of the particles are identical. In the first non-trivial case, $n=d+1$, we give a homogeneous system of parameters that is valid for the action of an arbitrary permutation symmetry and make a conjecture for the full Hironaka decomposition in the case without permutation symmetry. An appendix gives formulæ\ for the computation of the relevant Hilbert series for $d\le 4$.

    ↳ hep-thhep-phmath-phmath.MPJ.Phys.A(2021)·9 citations
33. 33*

    Recoil Momentum Effects in Quantum Processes Induced by Twisted Photons

    Andrei Afanasev🇺🇸 · Carl E. Carlson🇺🇸 · Asmita Mukherjee🇮🇳

    We consider physical processes caused by the twisted photons for a wide range of energy scales, from optical (eV) to nuclear (MeV) to high-energy gamma-rays (TeV). We demonstrate that in order to satisfy angular momentum conservation, absorption of a twisted photon leads to a transverse recoil of the final particle or a system of particles leading to increased threshold energy required for the reaction to proceed. Modification of the threshold energy is predicted for (a) Photo-absorption on colds trapped ions of ${}^{40}$Ca, along with emerging new transverse-motion sidebands, (b) photo-disintegration of deuterium and (c) photo-production of electron-positron pairs in astrophysics environment.

    ↳ quant-phastro-ph.HEhep-phnucl-thPRResearch(2021)·19 citations
34. 34*

    Double Hawking temperature in de Sitter Universe and cosmological constant problem

    G.E. Volovik🇫🇮

    As distinct from the black hole physics, the de Sitter thermodynamics is not determined by the cosmological horizon, the effective temperature differs from the Hawking temperature. In particular, the atom in the de Sitter universe experiences thermal activation corresponding to the local temperature, which is twice larger than the Hawking temperature, $T_{\mathrm{loc}}=2T_{\mathrm{Hawking}}$. The same double Hawking temperature describes the decay of massive scalar field in the de Sitter universe. The reason, why the local temperature is exactly twice the Hawking temperature, follows from the geometry of the de Sitter spacetime. The weakening of the role of the cosmological horizon in de Sitter universe is confirmed by considering Hawking radiation. We discuss the difference between the radiation of particles in the de Sitter spacetime and the Schwinger pair creation in the electric field. We use the stationary Painleve-Gullstrand metric for the de Sitter spacetime, where the particles are created by Hawking radiation from the cosmological horizon, and time independent gauge for the electric field. In these stationary frames the Hamiltonians and the energy spectra of massive particles look rather similar. However, the final results are essentially different. In case of Schwinger pair production the number density of the created pairs grows with time, while in the de Sitter vacuum the number density of the created pairs is finite. The latter suggests that Hawking radiation from the cosmological horizon does not lead to instability of the de Sitter vacuum. The other mechanisms of instability are required for the dynamical solution of the cosmological constant problem. We consider the possible role of the local temperature $T_{\mathrm{loc}}=2T_{\mathrm{H}}$ in the decay of the de Sitter space-time due to the energy exchange between the vacuum energy and relativistic matter with this temperature.

    ↳ gr-qccond-mat.otherhep-ph4 citations
35. 35*

    Modular symmetry by orbifolding magnetized $T^2\times T^2$: realization of double cover of ${\Gamma }_N$

    Shota Kikuchi🇯🇵 · Tatsuo Kobayashi🇯🇵 · Hajime Otsuka🇯🇵 · Shintaro Takada🇯🇵 · Hikaru Uchida🇯🇵

    We study the modular symmetry of zero-modes on $T_1^2\times T_2^2$ and orbifold compactifications with magnetic fluxes, $M_1,M_2$, where modulus parameters are identified. This identification breaks the modular symmetry of $T_1^2\times T_2^2$, $SL(2,\mathbb{Z}{)}_1\times SL(2,\mathbb{Z}{)}_2$ to $SL(2,\mathbb{Z})\equiv \Gamma$. Each of the wavefunctions on $T_1^2\times T_2^2$ and orbifolds behaves as the modular forms of weight 1 for the principal congruence subgroup $\Gamma$($N$), $N$ being 2 times the least common multiple of $M_1$ and $M_2$. Then, zero-modes transform each other under the modular symmetry as multiplets of double covering groups of ${\Gamma }_N$ such as the double cover of $S_4$.

    ↳ hep-thhep-phJHEP(2020)·104 citations
36. 36*

    Impurity Lattice Monte Carlo for Hypernuclei

    Dillon Frame🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪

    We consider the problem of including $\Lambda$ hyperons into the ab initio framework of nuclear lattice effective field theory. In order to avoid large sign oscillations in Monte Carlo simulations, we make use of the fact that the number of hyperons is typically small compared to the number of nucleons in the hypernuclei of interest. This allows us to use the impurity lattice Monte Carlo method, where the minority species of fermions in the full nuclear Hamiltonian is integrated out and treated as a worldline in Euclidean projection time. The majority fermions (nucleons) are treated as explicit degrees of freedom, with their mutual interactions described by auxiliary fields. This is the first application of the impurity lattice Monte Carlo method to systems where the majority particles are interacting. Here, we show how the impurity Monte Carlo method can be applied to compute the binding energy of the light hypernuclei. In this exploratory work we use spin-independent nucleon-nucleon and hyperon-nucleon interactions to test the computational power of the method. We find that the computational effort scales approximately linearly in the number of nucleons. The results are very promising for future studies of larger hypernuclear systems using chiral effective field theory and realistic hyperon-nucleon interactions, as well as applications to other quantum many-body systems.

    ↳ nucl-thhep-lathep-phphysics.comp-phEPJA(2020)·22 citations
37. 37*

    The glueball spectrum of SU(3) gauge theory in 3+1 dimension

    Andreas Athenodorou🇮🇹 · Michael Teper🇬🇧

    We calculate the low-lying glueball spectrum of the SU(3) lattice gauge theory in 3+1 dimensions for the range of beta up to beta=6.50 using the standard plaquette action. We do so for states in all the representations R of the cubic rotation group, and for both values of parity P and charge conjugation C. We extrapolate these results to the continuum limit of the theory using the confining string tension as our energy scale. We also present our results in units of the r0 scale and, from that, in terms of physical `GeV' units. For a number of these states we are able to identify their continuum spins J with very little ambiguity. We also calculate the topological charge Q of the lattice gauge fields so as to show that we have sufficient ergodicity throughout our range of beta, and we calculate the multiplicative renormalisation of Q as a function of beta. We also obtain the continuum limit of the SU(3) topological susceptibility.

    ↳ hep-lathep-phhep-thJHEP(2020)·187 citations
38. 38*

    Probing chemical freeze-out criteria in relativistic nuclear collisions with coarse grained transport simulations

    Tom Reichert🇩🇪 · Gabriele Inghirami🇫🇮 · Marcus Bleicher🇩🇪

    We introduce a novel approach based on elastic and inelastic scattering rates to extract the hyper-surface of the chemical freeze-out from a hadronic transport model in the energy range from E${}_{\mathrm{lab}}=1.23$ AGeV to $\sqrt{s_{\mathrm{NN}}}=62.4$ GeV. For this study, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model combined with a coarse-graining method is employed. The chemical freeze-out distribution is reconstructed from the pions through several decay and re-formation chains involving resonances and taking into account inelastic, pseudo-elastic and string excitation reactions. The extracted average temperature and baryon chemical potential are then compared to statistical model analysis. Finally we investigate various freeze-out criteria suggested in the literature. We confirm within this microscopic dynamical simulation, that the chemical freeze-out at all energies coincides with $⟨E⟩/⟨N⟩\approx 1$ GeV, while other criteria, like $s/T^3=7$ and $n_{\mathrm{B}}+n_{\bar{\mathrm{B}}}\approx 0.12$ fm${}^{-3}$ are limited to higher collision energies.

    ↳ nucl-thhep-phnucl-exEPJA(2020)·20 citations
39. 39*

    GW190425, GW190521 and GW190814: Three candidate mergers of primordial black holes from the QCD epoch

    Sebastien Clesse🇧🇪 · Juan Garcia-Bellido🇪🇸

    The two recent gravitational-wave events GW190425 and GW190814 from the third observing run of LIGO/Virgo have both a companion which is unexpected if originated from a neutron star or a stellar black hole, with masses $[1.6-2.5]M_{\odot }$ and $[2.5-2.7]M_{\odot }$ and merging rates $460_{-360}^{+1050}$ and $7_{-6}^{+16}$ events/yr/Gpc${}^3$ respectively, at 90\% c.l.. Moreover, the recent event GW190521 has black hole components with masses 67 and $91M_{\odot }$, and therefore lies in the so-called pair-instability mass gap, where there should not be direct formation of stellar black holes. The possibility that all of these compact objects are Primordial Black Holes (PBHs) is investigated. The known thermal history of the Universe predicts that PBH formation is boosted at the time of the QCD transition, inducing a peak in their distribution at this particular mass scale, and a bump around $30-50M_{\odot }$. We find that the merging rates inferred from GW190425, GW190521 and GW190814 are consistent with PBH binaries formed by capture in dense halos in the matter era or in the early universe. At the same time, the rate of black hole mergers around $30M_{\odot }$ and of sub-solar PBH mergers do not exceed the LIGO/Virgo limits. Such PBHs could explain a significant fraction, or even the totality of the Dark Matter, but they must be sufficiently strongly clustered in order to be consistent with current astrophysical limits.

    ↳ astro-ph.COgr-qchep-phPhys.Dark Univ.(2022)·197 citations
40. 40*

    Valence parton distribution of pion from lattice QCD: Approaching continuum

    Xiang Gao🇺🇸 · Luchang Jin🇺🇸 · Christos Kallidonis🇺🇸 · Nikhil Karthik🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Charles Shugert🇺🇸 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸

    We present a high-statistics lattice QCD determination of the valence parton distribution function (PDF) of the pion, with a mass of 300 MeV, using two very fine lattice spacings of $a=0.06$ fm and 0.04 fm. We reconstruct the $x$-dependent PDF, as well as infer the first few even moments of the PDF using leading-twist 1-loop perturbative matching framework. Our analyses use both RI-MOM and ratio-based schemes to renormalize the equal-time bi-local quark-bilinear matrix elements of pions boosted up to 2.4 GeV momenta. We use various model-independent and model-dependent analyses to infer the large-$x$ behavior of the valence PDF. We also present technical studies on lattice spacing and higher-twist corrections present in the boosted pion matrix elements.

    ↳ hep-lathep-exhep-phnucl-ex+1PRD(2020)·124 citations
41. 41*

    General scalar renormalisation group equations at three-loop order

    Tom Steudtner🇬🇧

    For arbitrary scalar QFTs in four dimensions, renormalisation group equations of quartic and cubic interactions, mass terms, as well as field anomalous dimensions are computed at three-loop order in the $\overline{\text{MS}}$ scheme. Utilising pre-existing literature expressions for a specific model, loop integrals are avoided and templates for general theories are obtained. We reiterate known four-loop expressions, and derive $\beta$ functions for scalar masses and cubic interactions from it. As an example, the results are applied to compute all renormalisation group equations in $U(n)\times U(n)$ scalar theories.

    ↳ hep-thhep-phJHEP(2020)·22 citations
42. 42*

    Stable bound states of $N$'s, $\Lambda$'s, and $\Xi$'s

    H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸

    We review our recent work about the stability of strange few-body systems containing $N$'s, $\Lambda$'s, and $\Xi$'s. We make use of local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nucleon-nucleon system and the latest updates of the hyperon-nucleon and hyperon-hyperon ESC08c Nijmegen potentials. We solve the three- and four-body bound-state problems by means of Faddeev equations and a generalized Gaussian variational method, respectively. The hypertriton, $\Lambda np$ $(I)J^P=(1/2)1/2^{+}$, is bound by 144 keV; the recently discussed $\Lambda nn$ $(I)J^P=(1/2)1/2^{+}$ system is unbound, as well as the $\Lambda \Lambda nn$ $(I)J^P=(1)0^{+}$system, being just above threshold. Our results indicate that the $\Xi NN$, $\Xi \Xi N$ and $\Xi \Xi NN$ systems with maximal isospin might be bound.

    ↳ nucl-thhep-phRev. Mex. F\'is. 63, 411-422 (2017)·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.