Mon·Oct 26, 2020Monday·October 26, 2020

1. 01*

   Froissaron and Maximal Odderon with spin-flip in $pp$ and $\bar{p}p$ high energy elastic scattering

   N. Bence🇺🇦 · A. Lengyel🇺🇦 · Z. Tarics🇺🇦 · E. Martynov🇺🇦 · G. Tersimonov🇺🇦

   We assume that the scattering amplitude is represented by Froissaron, Maximal Odderon as well as by standard Regge poles. From the fit to the data of $pp$ and $\bar{p}p$ scattering at high energy and not too large momentum transfers we found that this model taking into account the spin is available to describe not only the differential, total cross section and $\rho$, but also the existing experimental data on polarization.

   hep-ph5 citations
2. 02*

   Mapping Machine-Learned Physics into a Human-Readable Space

   Taylor Faucett🇺🇸 · Jesse Thaler🇺🇸 · Daniel Whiteson🇺🇸

   We present a technique for translating a black-box machine-learned classifier operating on a high-dimensional input space into a small set of human-interpretable observables that can be combined to make the same classification decisions. We iteratively select these observables from a large space of high-level discriminants by finding those with the highest decision similarity relative to the black box, quantified via a metric we introduce that evaluates the relative ordering of pairs of inputs. Successive iterations focus only on the subset of input pairs that are misordered by the current set of observables. This method enables simplification of the machine-learning strategy, interpretation of the results in terms of well-understood physical concepts, validation of the physical model, and the potential for new insights into the nature of the problem itself. As a demonstration, we apply our approach to the benchmark task of jet classification in collider physics, where a convolutional neural network acting on calorimeter jet images outperforms a set of six well-known jet substructure observables. Our method maps the convolutional neural network into a set of observables called energy flow polynomials, and it closes the performance gap by identifying a class of observables with an interesting physical interpretation that has been previously overlooked in the jet substructure literature.

   hep-phhep-exphysics.data-anPRD(2021)·53 citations
3. 03*

   The role of non-universal $Z$ couplings in explaining the $V_{us}$ anomaly

   Ashutosh Kumar Alok🇮🇳 · Amol Dighe🇮🇳 · Shireen Gangal🇮🇳 · Jacky Kumar🇨🇦

   The tension among measurements of $V_{us}$ from different channels, the so-called Cabibbo Angle Anomaly, can be interpreted as a signal of lepton flavor universality (LFU) violation in the $W$ boson couplings. We investigate this issue in the framework of effective field theory, keeping the gauge structure of the Standard Model (SM) unchanged. We introduce gauge-invariant dimension-6 effective operators that couple the Higgs doublet to leptons, thereby giving non-universal tree-level contributions to the couplings of electroweak gauge bosons. Due to the $SU(2{)}_L$ gauge symmetry, a tension arises between the $V_{us}$ measurements that are affected by new $W$ couplings, and the electroweak precision measurements, which are also affected by the new $Z$ couplings. We show that this tension can be alleviated by allowing additional sources of gauge-invariant couplings of $Z$ boson to left- or right-handed leptons, and find the optimal regions indicated by the current data in the Wilson-coefficient space. We illustrate our model-independent results with the examples of minimal extensions of the SM involving the vector-like lepton (VLL) models. We point out that dimension-6 operators coupling the Higgs doublet to leptons can affect the rate of $h\to \tau \tau$ decay significantly in general, however this effect is restricted to less than a per cent level for the minimal VLL models.

   hep-phhep-exNPB(2021)·21 citations
4. 04*

   Anomalous dimensions from gauge couplings in SMEFT with right-handed neutrinos

   Alakabha Datta🇺🇸 · Jacky Kumar🇨🇦 · Hongkai Liu🇺🇸 · Danny Marfatia🇺🇸

   Standard Model Neutrino Effective Field Theory (SMNEFT) is an effective theory with Standard Model (SM) gauge-invariant operators constructed only from SM and right-handed neutrino fields. For the full set of dimension-six SMNEFT operators, we present the gauge coupling terms of the one-loop anomalous dimension matrix for renormalization group evolution (RGE) of the Wilson coefficients between a new physics scale and the electroweak scale. We find that the SMNEFT operators can be divided into five subsets which are closed under RGE. Our results apply for both Dirac and Majorana neutrinos. We also discuss the operator mixing pattern numerically and comment on some interesting phenomenological implications.

   hep-phJHEP(2021)·31 citations
5. 05*

   Identical-particle (pion and kaon) femtoscopy in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with Therminator2 modeled with (3+1)D viscous hydrodynamics

   Pritam Chakraborty🇮🇳 · Ashutosh Kumar Pandey🇮🇳 · Sadhana Dash🇮🇳

   The three-dimensional femtoscopic correlations of pions and kaons are presented for Pb$-$Pb collisions at \rootsNN = 5.02 TeV within the framework of (3+1)D viscous hydrodynamics combined with THERMINATOR 2 code for statistical hadronization. The femtoscopic radii for pions and kaons are obtained as a function of pair transverse momentum and centrality in all three pair directions. The radii showed a decreasing trend with an increase of pair transverse momentum and transverse mass for all centralities. These observations indicate the presence of strong collectivity. A simple effective scaling of radii with pair transverse mass was observed for both pion and kaons.

   hep-phEPJA(2021)·6 citations
6. 06*

   Effective Field Theories and Lattice for Hard Probes

   Nora Brambilla🇩🇪

   Effective Quantum Field Theories and QCD Lattice methods have become more and more complementary and mutually supportive in the study of Hard Probes. I present some of the progress that this alliance already delivered and I discuss future opportunities.

   hep-phhep-latnucl-thPoS(2021)·2 citations
7. 07*

   Second Class Currents, Axial Mass and Nuclear Effects in Hyperon Production

   C. Thorpe🇬🇧 · J. Nowak🇬🇧 · K. Niewczas🇵🇱 · J. T. Sobczyk🇵🇱 · C. Juszczak🇵🇱

   We study the properties of the Cabibbo suppressed quasielastic production of $\Lambda$ and $\Sigma$ hyperons in antineutrino interactions with nuclei, including the effects of modified form factor axial mass, the second class current and SU(3) flavour violations. The hyperon and nucleon are subjected to the nuclear potential and the outgoing hyperon can undergo final state interactions. The hyperon potential has a significant effect on their production through absorption. We predict a significant enhancement of $\Lambda$ production compared with other hyperon production channels through $\Sigma \to \Lambda$ conversions. We produce predictions for several experiments by combining realistic neutrino energy distributions with suitable nuclear targets.

   hep-phPRC(2021)·15 citations
8. 08*

   Masses and decay widths of ${\Xi }_{c/b}$ and ${\Xi }_{c/b}^{\prime }$ baryons

   Roelof Bijker🇲🇽 · Hugo García-Tecocoatzi🇮🇹 · Alessandro Giachino🇮🇹 · Emmanuel Ortiz-Pacheco🇲🇽 · Elena Santopinto🇮🇹

   In this article, we present a complete classification of the negative parity ${\Xi }_{c/b}^{\prime }$ and ${\Xi }_{c/b}$ $P$-wave states: 7 belonging to the $SU(3)$ flavor sextet and 7 to the flavor anti-triplet, the calculation of the ${\Xi }_{c/b}^{\prime }$ and ${\Xi }_{c/b}$ strong partial decay widths into ${}^2{\Sigma }_c\bar{K}$, ${}^2{\Xi }_c^{{}^{\prime }}\pi$, ${}^2{\Sigma }_c\bar{K}$, ${}^4{\Xi }_c^{{}^{\prime }}\pi$, ${\Lambda }_c^{{}^{\prime }}\bar{K}$, ${\Xi }_c^{}\pi$ and ${\Xi }_c^{}\eta$ channels both within the Elementary Emission Model (EEM) and the ${}^3{P}_0$ model, and the calculation of the electromagnetic decay widths for ${\Xi }_{c/b}^{\prime }$ and ${\Xi }_{c/b}$ radiative decays. By means of the equal-spacing mass rule and by the analysis of the strong partial decay widths, we suggest possible assignments for the new LHCb ${\Xi }_c(2923)$, ${\Xi }_c(2939)$, and ${\Xi }_c(2965)$ states, as well as for the ${\Xi }_c$'s previously reported by Belle and BaBar. Our results can be tested by future experiments, at LHCb and Belle, disentangling the remaining missing piece of information, {\it i.e.} the quantum numbers. Finally, a comparison is made between a three-quark and a quark-diquark description of ${\Xi }_c$ states. Very recently the LHCb collaboration reported the observation of two new ${\Xi }_b$ states, namely ${\Xi }_b(6327{)}^0$ and ${\Xi }_b(6333)$, in ${\Lambda }_b^0{K}^{-}{\pi }^{+}$ channel with a statistical significance larger than nine standard deviations. The experimental masses and widths of these two states are consistent with our mass and width predictions for the doublet of D-wave excitations of the ${\Xi }_b$ system with $J_{{\Xi }_b(6327{)}^0}^P={\frac{3}{2}}^{+}$ and $J_{{\Xi }_b(6333{)}^0}^P={\frac{5}{2}}^{+}$.

   hep-phPRD(2022)·37 citations
9. 09*

   Transverse structure of electron in momentum space in basis light-front quantization

   Zhi Hu🇨🇳 · Siqi Xu🇨🇳 · Chandan Mondal🇨🇳 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸

   We investigate the leading-twist transverse momentum-dependent distribution functions (TMDs) for a physical electron, a spin-1/2 composite system consisting of a bare electron and a photon, using the Basis Light-front Quantization (BLFQ) framework. The light-front wave functions of the physical electron are obtained from the eigenvectors of the light-front QED Hamiltonian. We evaluate the TMDs using the overlaps of the light-front wave functions. The BLFQ results are found to be in excellent agreement with those TMDs calculated using lowest-order perturbation theory.

   hep-phPRD(2021)·27 citations
10. 10*

    One-Loop Electroweak Radiative Corrections to Bhabha Scattering in the Belle II Experiment

    A.G. Aleksejevs🇨🇦 · S.G. Barkanova🇨🇦 · Yu.M. Bystritskiy🇷🇺 · V.A. Zykunov🇷🇺

    The Standard Model radiative corrections to the Bhabha scattering process are considered within the one-loop approximation. Both virtual corrections and corrections for the real photon emission are taken into consideration. The calculation was performed at the energy assumed at the Belle II (Japan) facility.

    hep-phPhys.Part.Nucl.(2020)·2 citations
11. 11*

    Late-Time Dark Matter Oscillations and the Core-Cusp Problem

    James M. Cline🇨🇦 · Guillermo Gambini🇨🇦 · Samuel D. McDermott🇺🇸 · Matteo Puel🇨🇦

    The core-cusp problem persists as an unresolved tension between the predictions of $\Lambda$CDM cosmology and observations of dark matter (DM) profiles in dwarf spheroidal and other galaxies. We present a novel scenario for converting cusps into cores through reactivation of DM annihilation in galaxies at late times. This can happen in asymmetric DM models when there is a very small DM-number violating mass term that causes oscillations between DM and its antiparticle. Using analytic methods as well as gravitational N-body simulations, we show that this mechanism can robustly eliminate cusps from galactic DM profiles for light fermionic DM of mass $m_{\chi }\sim (0.1-1)$ GeV and a lighter mediator into which the DM can annihilate. We identify regions of parameter space where annihilation of DM particles is more efficient than elastic scattering at reducing the inner density of the DM profile. Dark matter annihilation is therefore a qualitatively distinct alternative to the mechanism of elastic self-interacting dark matter for addressing the cusp-core problem.

    hep-phastro-ph.COJHEP(2021)·5 citations
12. 12*

    Generalized parton distributions of light nuclei

    Sara Fucini🇮🇹 · Matteo Rinaldi🇮🇹 · Sergio Scopetta🇮🇹

    The measurement of nuclear generalized parton distributions (GPDs) in hard exclusive processes, such as deeply virtual Compton Scattering (DVCS), will be one of the main achievements of a new generation of experiments at high luminosity, such as those under way at the Jefferson Laboratory (JLab) with the 12 GeV electron beam and, above all, those planned at the future Electron Ion Collider. The CLAS collaboration at JLab has recently demonstrated the possibility to disentangle the two different channels of nuclear DVCS, the coherent and incoherent ones, a first step towards the measurement of GPDs of nuclei and of bound nucleons, respectively, opening new exciting perspectives in the field. In this scenario, theoretical precise calculations, ultimately realistic, become mandatory. Light nuclei, for which realistic studies are affordable and conventional nuclear effects can be safely estimated, so that possible exotic effects can be exposed, play an important role. The status of the calculation of GPDs for light nuclei will be summarized, in particular for ${}^3$He and ${}^4$He, and some updates will be presented. The prospects for the next years, related to the new series of measurements at future facilities, will be addressed.

    ↳ nucl-thhep-phFew Body Syst.(2021)·6 citations
13. 13*

    Investigation of ${\Xi }^{-}nn$ ($S=-2$) Hypernucleus in Low-energy Pionless Halo Effective Theory

    Ghanashyam Meher🇮🇳 · Udit Raha🇮🇳

    In the strangeness $S=-2$ sector, we study the ${\Xi }^{-}nn$ ($I=3/2,J^P={1/2}^{+}$) three-body system using pionless halo effective field theory (EFT), which provides a systematic model independent framework for assessing the feasibility of light particle-stable three-body bound states, utilizing low-energy universality. Here we take recourse to a simplistic speculation of the three-body system by eliminating the repulsive spin-singlet ${\Xi }^{-}n$ sub-system, while retaining the predominantly attractive (possibly bound) spin-triplet ${\Xi }^{-}n$ and the virtual bound spin-singlet $nn$ sub-system. In particular, a qualitative leading order EFT investigation by introducing a sharp momentum (ultraviolet) cut-off parameter ${\Lambda }_c$ into the Faddeev-like coupled integral equations, indicates a discrete scaling behavior akin to a renormalization group limit cycle, thereby suggesting the formal existence of Efimov states in the unitary limit, as ${\Lambda }_c\to \infty$. Our subsequent non-asymptotic analysis indicates that the three-body binding energy $B_3$ is sensitively dependent on the cut-off without the inclusion of three-body contact interactions. Furthermore, our analysis reproduces several values of the binding energy $B_3\sim 3-4$ MeV, predicted in context of existing potential models, with the regulator ${\Lambda }_c$ in the range, $\sim 350-460$ MeV. Finally, based on these model inputs for $B_3$, a ballpark estimate of the three-body scattering length in the range, $2.6-4.9$ fm, is naively constrained by our EFT analysis, ostensibly demonstrating the universal nature of three-body correlations that is likely to manifest themselves in a halo-bound ${\Xi }^{-}nn$ system.

    ↳ nucl-thhep-phEur.Phys.J.ST(2021)·2 citations
14. 14*

    Recent development of hydrodynamic modeling in heavy-ion collisions

    Chun Shen🇺🇸 · Li Yan🇨🇳

    We present a concise review of the recent development of relativistic hydrodynamics and its applications to heavy-ion collisions. Theoretical progress on the extended formulation of hydrodynamics towards out-of-equilibrium systems is addressed, emphasizing the so-called attractor solution. On the other hand, recent phenomenological improvements in the hydrodynamic modeling of heavy-ion collisions with respect to the ongoing Beam Energy Scan program, the quantitative characterization of transport coefficients in the three-dimensionally expanding quark-gluon plasma, the fluid description of small colliding systems, and some other interdisciplinary connections are discussed.

    ↳ nucl-thhep-phnucl-exNucl.Sci.Tech.·187 citations
15. 15*

    Unitarization of infinite-range forces: graviton-graviton scattering

    Diego Blas🇬🇧 · Jorge Martin Camalich🇪🇸 · Jose Antonio Oller🇪🇸

    A method to unitarize the scattering amplitude produced by infinite-range forces is developed and applied to Born terms. In order to apply $S$-matrix techniques, based on unitarity and analyticity, we first derive an $S$-matrix free of infrared divergences. This is achieved by removing a divergent phase factor due to the interactions mediated by the massless particles in the crossed channels, a procedure that is related to previous formalisms to treat infrared divergences. We apply this method in detail by unitarizing the Born terms for graviton-graviton scattering in pure gravity and we find a scalar graviton-graviton resonance with vacuum quantum numbers ($J^{PC}=0^{++}$) that we call the \textit{graviball}. Remarkably, this resonance is located below the Planck mass but deep in the complex $s$-plane (with $s$ the usual Mandelstam variable), so that its effects along the physical real $s$ axis peak for values significantly lower than this scale. We argue that the position and width of the graviball are reduced when including extra light fields in the theory. This could lead to phenomenological consequences in scenarios of quantum gravity with a large number of such fields or, in general, with a low-energy ultraviolet completion. We also apply this formalism to two non-relativistic potentials with exact known solutions for the scattering amplitudes: Coulomb scattering and an energy-dependent potential obtained from the Coulomb one with a zero at threshold. This latter case shares the same $J=0$ partial-wave projected Born term as the graviton-graviton case, except for a global factor. We find that the relevant resonance structure of these examples is reproduced by our methods, which represents a strong indication of their robustness.

    ↳ hep-thgr-qchep-phJHEP(2022)·22 citations
16. 16*

    Spontaneous Symmetry Breaking

    Andreas Aste🇨🇭

    The concept of spontaneous symmetry breaking (SSB) generally lacks a simple and intuitive introduction in the literature. This gap is filled by defining SSB in a universal context beyond its usual applications in physics and by discussing some very simple, but stunning examples of the phenomenon.

    ↳ math-phhep-phhep-thmath.MP0 citations
17. 17*

    Hyperons from Bi+Bi collisions at MPD-NICA: Preliminary analysis of production at generation, simulation and reconstruction level

    Alejandro Ayala🇲🇽 · Eleazar Cuautle🇲🇽 · Isabel Domínguez🇲🇽 · M. Rodríguez-Cahuantzi🇲🇽 · Ivonne Maldonado🇲🇽 · María Elena Tejeda-Yeomans🇲🇽

    An important observable to understand the properties of the matter produced in heavy-ion collisions is its strangeness content. Recent experimental results show that in semi-central collisions, the $\Lambda$ and $\bar{\Lambda }$ global polarization show differences that increase at low energies. This behaviour has been described using a model where these particles may be produced from two distinct density zones in the collision region: the core and the corona where QGP processes and p + p like reactions, respectively, are mainly at work. Using this idea, the polarization can be influenced by the relative abundance of these particles coming from either regions. In this work we show how to test this model in the MPD experiment.

    ↳ hep-exhep-phPhys.Part.Nucl.(2021)·4 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.