Tue·Jun 16, 2020Tuesday·June 16, 2020

1. 01*

   Searching for top quark pair production cross section at LHeC and FCC-eh

   B.Rezaei🇮🇷 · G.R.Boroun🇮🇷

   The deep inelastic scattering mode of $t\overline{t}$ pair production at the proposed LHeC and FCC-eh is considered. We present a method to extract the top reduced cross section related to the transversal structure function $F_2(x,Q^2)$ parameterization. Numerical calculations with known kinematics of the LHeC and FCC-eh colliders are demonstrated. The results obtained for charm and beauty pair production are comparable with the experimental data. We show that for a wide range of the momentum transfer into the top quark pair, the reduced cross section is well described by center-of-mass energies.

   hep-phEPL(2020)·3 citations
2. 02*

   ${\Lambda }_c^{+}$ fragmentation functions from pQCD approach and the Suzuki model

   Mahdi Delpasand🇮🇷 · S. Mohammad Moosavi Nejad🇮🇷 · Maryam Soleymaninia🇮🇷

   Through data analysis, we present new sets of nonperturbative fragmentation functions (FFs) for ${\Lambda }_c^{+}$ baryon both at leading and next-to-leading order (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the minimal subtraction factorization scheme with five massless quarks. The FFs are determined by fitting all available data of inclusive single ${\Lambda }_c^{+}$ baryon production in $e^{+}{e}^{-}$ annihilation taken by the OPAL Collaboration at CERN LEP1 and Belle Collaboration at KEKB. We also estimate the uncertainties in the ${\Lambda }_c^{+}$ FFs as well as in the corresponding observables. In a completely different approach based on the Suzuki model, we will theoretically calculate the ${\Lambda }_c^{+}$ FF from charm quark and present our result at leading order perturbative QCD framework. A comparison confirms a good consistency between both approaches. We will also apply the ${\Lambda }_c^{+}$ FFs to make theoretical predictions for the energy distribution of ${\Lambda }_c^{+}$ produced through the top quark decay, to be measured at the CERN LHC.

   hep-phPRD(2020)·22 citations
3. 03*

   Revisiting nonfactorizable contributions to factorization-forbidden decays of $B$ mesons to charmonium

   Ya-Qian Li🇨🇳 · Meng-Kun Jia🇨🇳 · Zhou Rui🇨🇳

   Motivated by the large rates of $B\to ({\chi }_{c0},{\chi }_{c2},h_c)K$ decays observed by the $BABAR$ and Belle collaborations, we investigate the nonfactorizable contributions to these factorization-forbidden decays, which can occur through a gluon exchange between the $c\bar{c}$ system and the spectator quark. Our numerical results demonstrate that the spectator contributions are capable of producing a large branching ratio consistent with the experiments. As a by-product, we also study the Cabibbo-suppressed decays, such as $B\to ({\chi }_{c0},{\chi }_{c2},h_c)\pi$ and the U-spin-related $B_s$ decay, which have so far received less theoretical and experimental attention. The calculated branching ratios reach the order of $10^{-6}$, which in within the scope of the Belle-II and LHCb experiments. Further, the $CP$-asymmetry parameters are also calculated for these decays. The obtained results are compared with the available experimental data and numbers from other predictions. We also investigate the sources of theoretical uncertainties in our calculation.

   hep-phCPC(2020)·5 citations
4. 04*

   Light-front holographic radiative transition form factors for light mesons

   Mohammad Ahmady🇨🇦 · Satvir Kaur🇮🇳 · Chandan Mondal🇨🇳 · Ruben Sandapen🇨🇦

   We predict the $\mathcal{V}\to \mathcal{P}\gamma$ decay widths and the $\mathcal{V}\to \mathcal{P}{\gamma }^{\ast }$ transition form factors, where $\mathcal{V}=(\rho ,\omega ,K^{\ast },\varphi )$ and $\mathcal{P}=(\pi ,K,\eta ,{\eta }^{\prime })$, using spin-improved holographic light-front wavefunctions for the mesons. We find excellent agreement with the available data for both the decay widths and the timelike transition form factors extracted from the leptonic conversion decays $\mathcal{V}\to \mathcal{P}{l}^{+}{l}^{-}$.

   hep-phPRD(2020)·16 citations
5. 05*

   Chiral Perturbation Theory Analysis of the Quark Condensate in a Magnetic Field

   Christoph P. Hofmann🇲🇽

   We present two-loop results for the quark condensate in an external magnetic field within chiral perturbation theory using coordinate space techniques. At finite temperature, we explore the impact of the magnetic field on the pion-pion interaction in the quark condensate for arbitrary pion masses and derive the correct weak magnetic field expansion in the chiral limit. At zero temperature, we provide the complete two-loop representation for the vacuum energy density and the quark condensate.

   hep-phhep-lathep-thPRD(2020)·14 citations
6. 06*

   Analysing the charged scalar boson contribution to the charged-current $B$ meson anomalies

   Jonathan Cardozo🇨🇴 · J. H. Muñoz🇨🇴 · Nestor Quintero🇨🇴 · Eduardo Rojas🇨🇴

   Experimental measurements collected by the BABAR, Belle, and LHCb experiments on different observables associated with the semileptonic transition $b\to c\tau {\bar{\nu }}_{\tau }$, indicate the existence of disagreement respect with the Standard Model predictions. We analyse the charged scalar boson contributions to these charged-current $B$ meson anomalies within the framework of two Higgs doublet model with the most general Yukawa couplings to quarks and leptons from the third generation, involving left-handed and right-handed (sterile) neutrinos. We perform a phenomenological study of the Yukawa couplings parameter space that accommodates these anomalies. We consider the most recent data from HFLAV world-average and Belle combination, and the upper limits $\mathrm{BR}(B_c^{-}\to {\tau }^{-}{\bar{\nu }}_{\tau })<30\%$ and $10\%$. In addition, we include in our study the prospect measurements on $R(D^{(\ast )})$ that the Belle II experiment could achieve and explore, for the first time, the future implications for the corresponding charged scalar Yukawa couplings. This analysis updates the existing literature and includes new important observables. Our results show that current experimental $b\to c\tau {\bar{\nu }}_{\tau }$ data and Belle II projection favor the interpretation of a charged scalar boson interacting with right-handed neutrinos. Furthermore, as a side analysis regarding the charged scalar boson interpretation, we revisit the relation between $R(D^{\ast })$ and $\mathrm{BR}(B_c^{-}\to {\tau }^{-}{\bar{\nu }}_{\tau })$ by investigating whether the claim that pseudoscalar new physics interpretations of $R(D^{\ast })$ are implausible due to the $B_c$ lifetime is still valid, to the light of the recent data and Belle II prospects on $R(D^{\ast })$. Lastly, we reexamine addressing the $R(D^{(\ast )})$ anomalies in the context of the 2HDM of Type II.

   hep-phhep-exJ.Phys.G(2021)·23 citations
7. 07*

   Current bounds and future prospects of light neutralino dark matter in NMSSM

   Rahool Kumar Barman🇮🇳 · Genevieve Bélanger🇫🇷 · Biplob Bhattacherjee🇮🇳 · Rohini Godbole🇮🇳 · Dipan Sengupta🇺🇸 · Xerxes Tata🇺🇸

   Unlike its minimal counterpart, the Next to Minimal supersymmetric Standard Model (NMSSM) allows the possibility that the lightest neutralino could have a mass as small as $\sim 1\mathrm{GeV}$ while still providing a significant component of relic dark matter (DM). Such a neutralino can provide an invisible decay mode to the Higgs as well. Further, the observed SM-like Higgs boson ($H_{125}$) could also have an invisible branching fraction as high as $\sim 19\%$. Led by these facts, we first delineate the region of parameter space of the NMSSM with a light neutralino ($M_{{\tilde{\chi }}_1^0}<62.5\mathrm{GeV}$) that yields a thermal neutralino relic density smaller than the measured relic density of cold dark matter, and is also compatible with constraints from collider searches, searches for dark matter, and from flavor physics. We then examine the prospects for probing the NMSSM with a light neutralino via direct DM detection searches, via invisible Higgs boson width experiments at future $e^{+}{e}^{-}$ colliders, via searches for a light singlet Higgs boson in $2b2\mu$, $2b2\tau$ and $2\mu 2\tau$ channels and via pair production of winos or doublet higgsinos at the high luminosity LHC and its proposed energy upgrade. For this last-mentioned electroweakino search, we perform a detailed analysis to map out the projected reach in the $3l+\mathrm{E}{/}_{\mathrm{T}}$ channel, assuming that chargino decays to $W{\tilde{\chi }}_1^0$ and the neutralino(s) decay to $Z$ or $H_{125}$ + ${\tilde{\chi }}_1^0$. We find that the HL-LHC can discover SUSY in just part of the parameter space in each of these channels, which together can probe almost the entire parameter space. The HE-LHC probes essentially the entire region with higgsinos (winos) lighter than 1 TeV (2 TeV) independently of how the neutralinos decay, and leads to significantly larger signal rates.

   hep-phPRD(2021)·25 citations
8. 08*

   An explanation for the muon and electron $g-2$ anomalies and dark matter

   Kai-Feng Chen🇹🇼 · Cheng-Wei Chiang🇹🇼 · Kei Yagyu🇯🇵

   We propose simple models with a flavor-dependent global $U(1{)}_{\ell }$ and a discrete ${\mathbb{Z}}_2$ symmetries to explain the anomalies in the measured anomalous magnetic dipole moments of muon and electron, $(g-2{)}_{\mu ,e}$, while simultaneously accommodating a dark matter candidate. These new symmetries are introduced not only to avoid the dangerous lepton flavor-violating decays of charged leptons, but also to ensure the stability of the dark matter. Our models can realize the opposite-sign contributions to the muon and electron $g-2$ via one-loop diagrams involving new vector-like leptons. Under the vacuum stability and perturbative unitarity bounds as well as the constraints from the dark matter direct searches and related LHC data, we find suitable parameter space to simultaneously explain $(g-2{)}_{\mu ,e}$ and the relic density. In this parameter space, the coupling of the Higgs boson with muons can be enhanced by up to $\sim 38\%$ from its Standard Model value, which can be tested in future collider experiments.

   hep-phJHEP(2020)·52 citations
9. 09*

   Anomalous scattering and transport in chiral matter

   Kirill Tuchin🇺🇸

   Chiral anomaly modifies the scattering processes in chiral systems which can be computed using the Maxwell-Chern-Simons theory that couples electrodynamics to the pseudoscalar field $\theta$ describing the topological charge induced be external sources. Assuming slow variation of the topological charge density, the fermion scattering cross section is computed in the Born approximation and is found to have a resonance at the scattering angles proportional to the chiral conductivity. As a result, the transport coefficients are suppressed at high temperatures. The anisotropy of the cross section arises due to the spatial variation of the topological charge; its effect on the electrical conductivity is discussed.

   hep-phcond-mat.mes-hallnucl-thPLB(2020)·7 citations
10. 10*

    Chiral anomaly and the pion properties in the light-front quark model

    Ho-Meoyng Choi (Kyungpook National University)🇰🇷 · Chueng-Ryong Ji (North Carolina State University)🇺🇸

    We explore the link between the chiral symmetry of QCD and the numerical results of the light-front quark model, analyzing both the two-point and three-point functions of the pion. Including the axial-vector coupling as well as the pseudoscalar coupling in the light-front quark model, we discuss the implication of the chiral anomaly in describing the pion decay constant, the pion-photon transition form factor and the electromagnetic form factor of the pion. In constraining the model parameters, we find that the chiral anomaly plays a critical role and the analysis of $F_{\pi \gamma }(Q^2)$ in timelike region is important. Our results indicate that the constituent quark picture is effective for the low and high $Q^2$ ranges implementing the quark mass evolution effect as $Q^2$ grows.

    hep-phnucl-thPRD(2020)·10 citations
11. 11*

    Masses of doubly heavy tetraquarks $T_{Q{Q}^{\prime }}$ in a relativized quark model

    Qi-Fang Lü🇨🇳 · Dian-Yong Chen🇨🇳 · Yu-Bing Dong🇨🇳

    In the present work, the mass spectra of doubly heavy tetraquarks $T_{Q{Q}^{\prime }}$ are systematically investigated in a relativized quark model. The four-body systems including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved within the variational method. Our results suggest that the $I{J}^P=01^{+}$ $bb\bar{u}\bar{d}$ state is 54 MeV below the relevant $\bar{B}\bar{B}$ and $\bar{B}{\bar{B}}^{\ast }$ thresholds, which indicates that both strong and electromagnetic decays are forbidden, and thus this state can be a stable one. Its large hidden color component and small root mean square radius demonstrate that it is a compact tetraquark rather than a loosely bound molecule or point-like diquark-antidiquark structure. Our predictions of the doubly heavy tetraquarks may provide valuable information for future experimental searches.

    hep-phhep-exnucl-thPRD(2020)·93 citations
12. 12*

    Triple-pomeron amplitude in the effective action approach

    M.A.Braun🇷🇺

    In the effective action approach the imaginary part of the triple pomeron amplitude is calculated. The found dependence on the longitudinal momentum transfer $\text{e}$ is found to separate as a simple factor $1/|\text{e}|$. This result is used to calculate the high-mass diffraction on a hadron and double scattering cross-section off a composite target}

    hep-phEPJC(2020)·2 citations
13. 13*

    Resonance contributions $\varphi (1020,1680)\to K\bar{K}$ for the three-body decays $B\to K\bar{K}h$

    Ying-Ying Fan🇨🇳 · Wen-Fei Wang🇨🇳

    We study the contributions for the $K^{+}{K}^{-}$ and $K^0{\bar{K}}^0$ originated from the intermediate states $\varphi (1020)$ and $\varphi (1680)$ in the charmless three-body decays $B\to K\bar{K}h$, with $h=(\pi ,K)$, in the perturbative QCD approach. The subprocesses $\varphi (1020,1680)\to K\bar{K}$ are introduced into the distribution amplitudes of $K\bar{K}$ system via the kaon electromagnetic form factors with the coefficients taken from the fitted results. The predictions of the branching fractions for the decays $B\to \varphi (1680)h$ with the intermediate state $\varphi (1680)$ decays into $K^{+}{K}^{-}$ or $K^0{\bar{K}}^0$ are about $6\%$-$8\%$ of the corresponding results for the quasi-two-body decays $B\to \varphi (1020)h\to K^{+}{K}^{-}h$ in this work.

    hep-phEPJC(2020)·16 citations
14. 14*

    Bubble dynamics in a strong first-order quark-hadron transition

    Shuying Zhou🇨🇳 · Song Shu🇨🇳 · Hong Mao🇨🇳

    We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interaction via homogeneous bubble nucleation in the Friedberg-Lee model. The one-loop effective thermodynamics potential of the model and the critical bubble profiles have been calculated at different temperatures and chemical potentials. By taking the temperature and the chemical potential as the variables, the evolutions of the surface tension, the typical radius of the critical bubble and the shift in the coarse-grained free energy in the presence of a nucleation bubble are obtained and the limit on the reliability of the thin-wall approximation is also addressed accordingly. Our results are compared to those obtained for a weak first-order quark-hadron phase transition, especially the spinodal decomposition is relevant.

    hep-phnucl-thCPC(2021)·8 citations
15. 15*

    Dark photons from pions produced in ultraperipheral $PbPb$ collisions

    V. P. Goncalves🇧🇷 · B. D. Moreira🇧🇷

    In this letter we propose the search of dark photons in the decay of pions produced by $\gamma \gamma$ interactions in ultraperipheral $PbPb$ collisions. The cross section is estimated considering an accurate treatment for the absorptive corrections and for the nuclear form factor. Predictions for the event rates are presented considering the expected luminosities for the LHC, High -- Luminosity LHC and High -- Energy LHC as well as for the Future Circular Collider. Our results indicate that a future experimental analysis of the pion production in ultraperipheral heavy ion collisions can be useful to probe the dark photon production and constrain its properties.

    hep-phhep-exPLB(2020)·5 citations
16. 16*

    Reanalysis of low-energy electron-proton scattering data and proton radius

    Dmitry Borisyuk🇺🇦 · Alexander Kobushkin🇺🇦

    We reanalyze electron-proton scattering data in the momentum transfer region $Q^2<1Ge{V}^2$, which were used to determine proton electric radius, with main focus on the Mainz experiment (Bernauer et al., 2010). We examine dependence of fit results and ${\chi }^2$ on the cut-off in $Q^2$ and degree of fitting polynomial, using pseudo-data and compare it with the case of real experimental data. We find that under some assumptions, the data could be consistent with the radius, obtained from muonic hydrogen.

    hep-phNPA(2020)·4 citations
17. 17*

    QCD traveling waves phenomenology revisited

    J. T. Amaral🇧🇷 · D. A. Fagundes🇧🇷 · M. V. T. Machado🇧🇷

    In this paper we review and update the Amaral-Gay Ducati-Betemps-Soyez saturation model, by testing it against the recent H1-ZEUS combined data on deep inelastic scattering, including heavy quarks in the dipole amplitude. We obtain that this model, which is based on traveling wave solutions of the Balitsky-Kovchegov equation and built in the momentum space framework, yields very accurate descriptions of the reduced cross section, ${\sigma }_r(x,y,Q^2)$, as well as DIS structure functions such as $F_2(x,Q^2)$ and $F_L(x,Q^2)$, all measured at HERA. Additionally, it provides good descriptions of heavy quark structure functions, $F_2^{cc}$ and $F_2^{bb}$ at small-$x$ and $Q^2\lesssim 60$ GeV${}^2$. We also use the improved model to make predictions for structure functions to be measured in the near future at LHeC.

    hep-phPRD(2021)·7 citations
18. 18*

    Study of the potential transverse momentum and potential angular momentum within the scalar diquark model

    David Arturo Amor-Quiroz🇫🇷 · Matthias Burkardt🇺🇸 · William Focillon🇫🇷 · Cédric Lorcé🇫🇷

    We make use of a simple scalar diquark model to study the potential transverse momentum and potential angular momentum, defined as the difference between the Jaffe-Manohar and Ji notions of transverse momentum and orbital angular momentum, respectively. A non-vanishing potential angular momentum has been previously found in lattice calculations and is believed to appear due to the effects of initial/final state interactions between the spectator system and the struck quark in high energy scattering processes. Such re-scattering phenomena are similar in nature to those who are responsible for generating the Sivers shift. This motivates us to search for an estimate of the potential angular momentum in terms of the expectation value of the transverse momentum of the struck quark.

    hep-phhep-th0 citations
19. 19*

    Dark Initial State Radiation and the Kinetic Mixing Portal

    Thomas G. Rizzo🇺🇸

    Data from Planck measurements of the cosmic microwave background (CMB) place important constraints on models with light dark matter (DM) and light mediators especially when both lie in the mass range below $\sim 1$ GeV. In models involving kinetic mixing where the dark photon acts as the mediator, these constraints are easily satisfied and the appropriate DM relic density achievable if the DM is, e.g., a complex scalar, where $p$-wave annihilation occurs, or is the lighter component of a split pseudo-Dirac state where co-annihilation dominates. In both of these cases, although higher order in the dark gauge coupling, $g_D$, the corresponding annihilation processes including dark photon initial state radiation (ISR) will be dominantly $s$-wave with essentially temperature independent cross sections. The rates for these dark ISR associated processes, though not yielding cross sections large enough to contribute to the relic density, can still run into possible conflicts with the bounds arising from the CMB. In this paper we perform a preliminary study of the present and potential future constraints that the CMB imposes on the parameter spaces for both of these scenarios due to the existence of this dark ISR. Further analyses of the effects of dark ISR in DM annihilation is clearly warranted.

    hep-phJHEP(2021)·14 citations
20. 20*

    Derivative couplings in gravitational production in the early universe

    Daniel E. Borrajo Gutiérrez🇪🇸 · Jose A. R. Cembranos🇪🇸 · Luis J. Garay🇪🇸 · Jose M. Sánchez Velázquez🇪🇸

    Gravitational particle production in the early universe is due to the coupling of matter fields to curvature. This coupling may include derivative terms that modify the kinetic term. The most general first order action contains derivative couplings to the curvature scalar and to the traceless Ricci tensor, which can be dominant in the case of (pseudo-)Nambu-Goldstone bosons or disformal scalars, such as branons. In the presence of these derivative couplings, the density of produced particles for the adiabatic regime in the de Sitter phase (which mimics inflation) is constant in time and decays with the inverse effective mass (which in turn depends on the coupling to the curvature scalar). In the reheating phase following inflation, the presence of derivative couplings to the background curvature modifies in a nontrivial way the gravitational production even in the perturbative regime. We also show that the two couplings -- to the curvature scalar and to the traceless Ricci tensor -- are drastically different, specially for large masses. In this regime, the production becomes highly sensitive to the former coupling while it becomes independent of the latter.

    hep-phhep-thJHEP(2020)·6 citations
21. 21*

    Feynman Lectures on the Strong Interactions

    Richard P. Feynman🇺🇸 · James M. Cline🇨🇦

    These twenty-two lectures, with exercises, comprise the extent of what was meant to be a full-year graduate-level course on the strong interactions and QCD, given at Caltech in 1987-88. The course was cut short by the illness that led to Feynman's death. Several of the lectures were finalized in collaboration with Feynman for an anticipated monograph based on the course. The others, while retaining Feynman's idiosyncrasies, are revised similarly to those he was able to check. His distinctive approach and manner of presentation are manifest throughout. Near the end he suggests a novel, nonperturbative formulation of quantum field theory in $D$ dimensions. Supplementary material is provided in appendices and ancillary files, including verbatim transcriptions of three lectures and the corresponding audiotaped recordings.

    hep-phhep-thphysics.hist-ph0 citations
22. 22*

    Neutrino (Antineutrino)-Nucleus Interactions in the Shallow- and Deep-Inelastic Scattering Regions

    M. Sajjad Athar🇮🇳 · Jorge G. Morfin🇺🇸

    In $\nu /\bar{\nu }$-N/A interactions SIS is technically defined in terms of the four-momentum transfer to the hadronic system as non-resonant meson production with $Q^2⪅1Ge{V}^2$. This non-resonant meson production intermixes with resonant meson production in a regime of similar effective hadronic mass W of the interaction. As $Q^2$ grows and surpasses this $\approx 1Ge{V}^2$ limit, non-resonant interactions begin to take place with quarks within the nucleon indicating the start of DIS region. SIS and DIS regions have received varying degrees of attention from the community. While the theoretical / phenomenological study of $\nu$-nucleon and $\nu$-nucleus DIS scattering is advanced, such studies of a large portion of the SIS region, particularly the SIS to DIS transition region, have hardly begun. Experimentally, the SIS and the DIS regions for $\nu$-nucleon scattering have minimal results and only in the experimental study of the $\nu$-nucleus DIS region are there significant results for some nuclei. Since current and future neutrino oscillation experiments have contributions from both higher W SIS and DIS kinematic regions and these regions are in need of both considerable theoretical and experimental study, this review will concentrate on these SIS to DIS transition and DIS kinematic regions surveying our knowledge and the current challenges.

    hep-phhep-exnucl-thJ.Phys.G(2021)·70 citations
23. 23*

    Weinberg dimension-5 operator by vector-like lepton doublets

    Pei-Hong Gu🇨🇳

    It is well known that a Weinberg dimension-5 operator for small neutrino masses can be realized at tree level in three types of renormalizable models: (i) the type-I seesaw mediated by fermion singlets, (ii) the type-II seesaw mediated by Higgs triplets, (iii) the type-III seesaw mediated by fermion triplets. We here point out such operator can be also induced at tree level by vector-like lepton doublets in association with unusual fermion singlets, Higgs triplets or fermion triplets. If these unusual fermion singlets, Higgs triplets or fermion triplets are heavy enough, their decays can generate a lepton asymmetry to explain the cosmic baryon asymmetry, meanwhile, the vector-like lepton doublets can lead to a novel inverse or linear seesaw with rich observable phenomena. We further specify our scenario can be naturally embedded into a grand unification theory without the conventional type-I, type-II or type-III seesaw.

    hep-ph3 citations
24. 24*

    Determining the nuclear neutron distribution from Coherent Elastic neutrino-Nucleus Scattering: current results and future prospects

    Pilar Coloma🇪🇸 · Ivan Esteban🇪🇸 · M.C. Gonzalez-Garcia🇪🇸 · Javier Menendez🇪🇸

    Coherent elastic neutrino-nucleus scattering (CE$\nu$NS), a process recently measured for the first time at ORNL's Spallation Neutron Source, is directly sensitive to the weak form factor of the nucleus. The European Spallation Source (ESS), presently under construction, will generate the most intense pulsed neutrino flux suitable for the detection of CE$\nu$NS. In this paper we quantify its potential to determine the root mean square radius of the point-neutron distribution, for a variety of target nuclei and a suite of detectors. To put our results in context we also derive, for the first time, a constraint on this parameter from the analysis of the energy and timing data of the CsI detector at the COHERENT experiment.

    hep-phhep-exnucl-exnucl-thJHEP(2020)·53 citations
25. 25*

    Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: II. Spin polarizabilities and moments of polarized structure functions

    Jose Manuel Alarcón (U. Complutense de Madrid & IPARCOS)🇪🇸 · Franziska Hagelstein (AEC Bern)🇨🇭 · Vadim Lensky🇩🇪 · Vladimir Pascalutsa (JGU Mainz)🇩🇪

    We examine the polarized doubly-virtual Compton scattering (VVCS) off the nucleon using chiral perturbation theory ($\chi$PT). The polarized VVCS contains a wealth of information on the spin structure of the nucleon which is relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of the polarized VVCS amplitudes $S_1(\nu ,Q^2)$ and $S_2(\nu ,Q^2)$, and the corresponding polarized spin structure functions $g_1(x,Q^2)$ and $g_2(x,Q^2)$. Our results for the moments of polarized structure functions, partially related to different spin polarizabilities, are compared to other theoretical predictions and "data-driven" evaluations, as well as to the recent Jefferson Lab measurements. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant baryon $\chi$PT (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.

    hep-phhep-latnucl-exnucl-th+1PRD(2020)·22 citations
26. 26*

    Parton distributions and lattice QCD calculations: toward 3D structure

    Martha Constantinou🇺🇸 · Aurore Courtoy🇲🇽 · Markus A. Ebert🇺🇸 · Michael Engelhardt🇺🇸 · Tommaso Giani🇬🇧 · Tim Hobbs🇺🇸 · Tie-Jiun Hou🇨🇳 · Aleksander Kusina🇵🇱 · Krzysztof Kutak🇵🇱 · Jian Liang🇺🇸 · Huey-Wen Lin🇺🇸 · Keh-Fei Liu🇺🇸 and 15 other authors

    The strong force which binds hadrons is described by the theory of Quantum Chromodynamics (QCD). Determining the character and manifestations of QCD is one of the most important and challenging outstanding issues necessary for a comprehensive understanding of the structure of hadrons. Within the context of the QCD parton picture, the Parton Distribution Functions (PDFs) have been remarkably successful in describing a wide variety of processes. However, these PDFs have generally been confined to the description of collinear partons within the hadron. New experiments and facilities provide the opportunity to additionally explore the transverse structure of hadrons which is described by Generalized Parton Distributions (GPDs) and Transverse Momentum Dependent Parton Distribution Functions (TMD PDFs). In our previous review, we compared and contrasted the two main approaches used to determine the collinear PDFs: the first based on perturbative QCD factorization theorems, and the second based on lattice QCD calculations. In the present report, we provide an update of recent progress on the collinear PDFs, and also expand the scope to encompass the generalized PDFs (GPDs and TMD PDFs). We review the current state of the various calculations, and consider what new data might be available in the near future. We also examine how a shared effort can foster dialog between the PDF and Lattice QCD communities, and yield improvements for these generalized PDFs.

    hep-phhep-latPPNP(2021)·257 citations
27. 27*

    Casting a graph net to catch dark showers

    Elias Bernreuther🇩🇪 · Thorben Finke🇩🇪 · Felix Kahlhoefer🇩🇪 · Michael Krämer🇩🇪 · Alexander Mück🇩🇪

    Strongly interacting dark sectors predict novel LHC signatures such as semi-visible jets resulting from dark showers that contain both stable and unstable dark mesons. Distinguishing such semi-visible jets from large QCD backgrounds is difficult and constitutes an exciting challenge for jet classification. In this article we explore the potential of supervised deep neural networks to identify semi-visible jets. We show that dynamic graph convolutional neural networks operating on so-called particle clouds outperform convolutional neural networks analysing jet images as well as other neural networks based on Lorentz vectors. We investigate how the performance depends on the properties of the dark shower and discuss training on mixed samples as a strategy to reduce model dependence. By modifying an existing mono-jet analysis we show that LHC sensitivity to dark sectors can be enhanced by more than an order of magnitude by using the dynamic graph network as a dark shower tagger.

    hep-phhep-exSciPost Phys.(2021)·78 citations
28. 28*

    About detecting very low mass black holes in LAr detectors

    Ionel Lazanu🇷🇴 · Sorina Lazanu🇷🇴 · Mihaela Pârvu🇷🇴

    The nature of dark matter is still an open problem. The simplest assumption is that gravity is the only force coupled certainly to dark matter and thus the micro black holes could be a viable candidate. We investigated the possibility of direct detection of micro black holes with masses around and upward the Planck scale (10${}^{-5}$ g), ensuring classical gravitational treatment of these objects in the next generation of huge LAr detectors. We show that the signals (ionization and scintillation) produced in LAr enable the discrimination between micro black holes or other particles. It is expected that the trajectories of these micro black holes will appear as crossing the whole active medium, in any direction, producing uniform ionization and scintillation on all the path.

    hep-phastro-ph.IMphysics.ins-detJCAP(2020)·7 citations
29. 29*

    Inference offers a metric to constrain dynamical models of neutrino flavor transformation

    Eve Armstrong🇺🇸 · Amol V. Patwardhan🇺🇸 · Ermal Rrapaj🇺🇸 · Sina Fallah Ardizi🇺🇸 · George M. Fuller🇺🇸

    The multi-messenger astrophysics of compact objects presents a vast range of environments where neutrino flavor transformation may occur and may be important for nucleosynthesis, dynamics, and a detected neutrino signal. Development of efficient techniques for surveying flavor evolution solution spaces in these diverse environments, which augment and complement existing sophisticated computational tools, could leverage progress in this field. To this end we continue our exploration of statistical data assimilation (SDA) to identify solutions to a small-scale model of neutrino flavor transformation. SDA is a machine learning (ML) formula wherein a dynamical model is assumed to generate any measured quantities. Specifically, we use an optimization formulation of SDA wherein a cost function is extremized via the variational method. Regions of state space in which the extremization identifies the global minimum of the cost function will correspond to parameter regimes in which a model solution can exist. Our example study seeks to infer the flavor transformation histories of two mono-energetic neutrino beams coherently interacting with each other and with a matter background. We require that the solution be consistent with measured neutrino flavor fluxes at the point of detection, and with constraints placed upon the flavor content at various locations along their trajectories, such as the point of emission, and the locations of the Mikheyev-Smirnov-Wolfenstein (MSW) resonances. We show how the procedure efficiently identifies solution regimes and rules out regimes where solutions are infeasible. Overall, results intimate the promise of this "variational annealing" methodology to efficiently probe an array of fundamental questions that traditional numerical simulation codes render difficult to access.

    ↳ astro-ph.HEhep-phPRD(2020)·8 citations
30. 30*

    Neutrino mixing in nuclear rapid neutron-capture processes

    M. M. Saez🇦🇷 · O. Civitarese🇦🇷 · M. E. Mosquera🇦🇷

    A possible mechanism for the formation of heavy-mass elements in supernovae is the rapid neutron-capture-mechanism (r-process). It depends upon the electron-fraction $Y_e$, a quantity which is determined by beta-decay-rates. In this paper, we focus on the calculation of electroweak decay-rates in presence of massive neutrinos. The resulting expressions are then used to calculate nuclear reactions entering the rapid-neutron capture. We fix the astrophysical parameters to the case of a core-collapse supernova. The neutrino sector includes a mass scheme and mixing angles for active neutrinos, and also by including the mixing between active and sterile neutrinos. The results of the calculations show that the predicted abundances of heavy-mass nuclei are indeed affected by the neutrino mixing.

    ↳ nucl-thhep-phIJMPE(2020)·1 citation
31. 31*

    Searching for Anisotropic Cosmic Birefringence with Polarization Data from SPTpol

    F. Bianchini🇦🇺 · W. L. K. Wu🇺🇸 · P. A. R. Ade🇬🇧 · A. J. Anderson🇺🇸 · J. E. Austermann🇺🇸 · J. S. Avva🇺🇸 · L. Balkenhol🇦🇺 · E. Baxter🇺🇸 · J. A. Beall🇺🇸 · A. N. Bender🇺🇸 · B. A. Benson🇺🇸 · L. E. Bleem🇺🇸 and 60 other authors

    We present a search for anisotropic cosmic birefringence in 500 deg${}^2$ of southern sky observed at 150 GHz with the SPTpol camera on the South Pole Telescope. We reconstruct a map of cosmic polarization rotation anisotropies using higher-order correlations between the observed cosmic microwave background (CMB) $E$ and $B$ fields. We then measure the angular power spectrum of this map, which is found to be consistent with zero. The non-detection is translated into an upper limit on the amplitude of the scale-invariant cosmic rotation power spectrum, $L(L+1)C_L^{\alpha \alpha }/2\pi <0.10\times 10^{-4}$ rad${}^2$ (0.033 deg${}^2$, 95% C.L.). This upper limit can be used to place constraints on the strength of primordial magnetic fields, $B_{1\mathrm{Mpc}}<17\mathrm{nG}$ (95% C.L.), and on the coupling constant of the Chern-Simons electromagnetic term $g_{a\gamma }<4.0\times 10^{-2}/H_I$ (95% C.L.), where $H_I$ is the inflationary Hubble scale. For the first time, we also cross-correlate the CMB temperature fluctuations with the reconstructed rotation angle map, a signal expected to be non-vanishing in certain theoretical scenarios, and find no detectable signal. We perform a suite of systematics and consistency checks and find no evidence for contamination.

    ↳ astro-ph.COhep-phPRD(2020)·89 citations
32. 32*

    More on the three-gluon vertex in SU(2) Yang-Mills theory in three and four dimensions

    Axel Maas🇦🇹 · Milan Vujinović🇦🇹

    The three-gluon vertex has been found to be a vital ingredient in non-perturbative functional approaches. We present an updated lattice calculation of it in various kinematical configurations for all tensor structures and multiple lattice parameters in three dimensions, and in a subset of those in four dimensions, for SU(2) Yang-Mills theory in minimal Landau gauge. In three dimensions an unambiguous zero crossing for the tree-level form-factor is established, and consistency for all investigated form factors with a power-like divergence towards the infrared is observed. Using very coarse lattices this is even seen towards momenta as low as about 15 MeV. The results in four dimensions are consistent with such a behavior, but do not yet reach deep enough into the infrared to establish it.

    ↳ hep-lathep-phSciPost Phys.Core(2022)·16 citations
33. 33*

    Gravitational shock waves and scattering amplitudes

    Andrea Cristofoli🇩🇰

    We study gravitational shock waves using scattering amplitude techniques. After first reviewing the derivation in General Relativity as an ultrarelativistic boost of a Schwarzschild solution, we provide an alternative derivation by exploiting a novel relation between scattering amplitudes and solutions to Einstein's field equations. We prove that gravitational shock waves arise from the classical part of a three point function with two massless scalars and a graviton. The region where radiation is localized has a distributional profile and it is now recovered in a natural way, thus bypassing the introduction of singular coordinate transformations as used in General Relativity. The computation is easily generalized to arbitrary dimensions and we show how the exactness of the classical solution follows from the absence of classical contributions at higher loops. A classical double copy between gravitational and electromagnetic shock waves is also provided and for a spinning source, using the exponential form of three point amplitudes, we infer a remarkable relation between gravitational shock waves and spinning ones, also known as gyratons. Using this property, we infer a family of exact solutions describing gravitational shock waves with spin. We then compute the phase shift of a particle in a background of shock waves finding agreement with an earlier computation by Amati, Ciafaloni and Veneziano for particles in the high energy limit. Applied to a gyraton, it provides a result for the scattering angle to all orders in spin.

    ↳ hep-thgr-qchep-phJHEP(2020)·80 citations
34. 34*

    The Newman-Penrose Map and the Classical Double Copy

    Gilly Elor🇺🇸 · Kara Farnsworth🇨🇿 · Michael L. Graesser🇺🇸 · Gabriel Herczeg🇺🇸

    Gauge-gravity duality is arguably our best hope for understanding quantum gravity. Considerable progress has been made in relating scattering amplitudes in certain gravity theories to those in gauge theories---a correspondence dubbed the "double copy". Recently, double copies have also been realized in a classical setting, as maps between exact solutions of gauge theories and gravity. We present here a novel map between a certain class of real, exact solutions of Einstein's equations and self-dual solutions of the flat-space vacuum Maxwell equations. This map, which we call the "Newman-Penrose map", is well-defined even for non-vacuum, non-stationary spacetimes, providing a systematic framework for exploring gravity solutions in the context of the double copy that have not been previously studied in this setting. To illustrate this, we present here the Newman-Penrose map for the Schwarzschild and Kerr black holes, and Kinnersley's photon rocket.

    ↳ hep-thgr-qchep-phJHEP(2020)·83 citations
35. 35*

    Axion Miniclusters Made Easy

    David Ellis🇩🇪 · David J. E. Marsh🇩🇪 · Christoph Behrens🇩🇪

    We use a modified version of the Peak Patch excursion set formalism to compute the mass and size distribution of QCD axion miniclusters from a fully non-Gaussian initial density field obtained from numerical simulations of axion string decay. We find strong agreement with N-Body simulations at a significantly lower computational cost. We employ a spherical collapse model and provide fitting functions for the modified barrier in the radiation era. The halo mass function at $z=629$ has a power-law distribution $M^{-0.6}$ for masses within the range $10^{-15}\lesssim M\lesssim 10^{-10}{M}_{\odot }$, with all masses scaling as $(m_a/50\mu \mathrm{eV}{)}^{-0.5}$. We construct merger trees to estimate the collapse redshift and concentration mass relation, $C(M)$, which is well described using analytical results from the initial power spectrum and linear growth. Using the calibrated analytic results to extrapolate to $z=0$, our method predicts a mean concentration $C\sim \mathcal{O}(\text{few})\times 10^4$. The low computational cost of our method makes future investigation of the statistics of rare, dense miniclusters easy to achieve.

    ↳ astro-ph.COhep-phPRD(2021)·52 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.