Fri·Mar 19, 2021Friday·March 19, 2021

1. 01*

   Quark and Gluon Contents of a Lepton at High Energies

   Tao Han🇺🇸 · Yang Ma🇺🇸 · Keping Xie🇺🇸

   In high-energy leptonic collisions, such as at a multi-TeV muon collider, the collinear splittings of the electroweak (EW) gauge bosons and leptons are the dominant phenomena, and the scattering processes should thus be formulated in terms of the EW parton distribution functions (EW PDFs). We complete this formalism in the Standard Model to include the QCD sector and evaluate the quark and gluon PDFs inside a lepton at the double-log accuracy. The splittings of the photon and subsequently the quarks and gluons control the quark/gluon PDFs below the EW scale. The massive gauge bosons lead to substantial contributions at high scales. The jet production cross section can reach the order of a few nb (50 pb) in $e^{+}{e}^{-}$ (${\mu }^{+}{\mu }^{-}$) collisions, at the TeV c.m. energies with a moderate acceptance cut, that governs the overall event shape up to about $p_T^j\sim 60$ GeV.

   hep-phhep-exhep-thJHEP(2022)·94 citations
2. 02*

   $N^{\ast }$ states with hidden charm and a three-body nature

   Brenda B. Malabarba🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷

   In this work we study the formation of $N^{\ast }$'s as a consequence of the dynamics involved in the $ND{\bar{D}}^{\ast }-N\bar{D}{D}^{\ast }$ system when the $D{\bar{D}}^{\ast }-\bar{D}{D}^{\ast }$ subsystem generates $X(3872)$ in isospin 0 and $Z_c(3900)$ in isospin 1. States with isospin $I=1/2$ and mass in the energy region $4400-4600$ MeV are found to arise with spin-parity $J^P=1/2^{+}$ and $3/2^{+}$, leading to predictions in this way of the existence of $N^{\ast }$ resonances with hidden charm and a three-body nature. We also discuss the possibility of the existence of ${\Delta }_c$ states, i.e., $\Delta$'s with hidden charm.

   hep-phnucl-thEPJA(2022)·13 citations
3. 03*

   Light-front holography with chiral symmetry breaking

   Yang Li🇨🇳 · James P. Vary🇺🇸

   We present an analytically solvable 3D light-front Hamiltonian model for hadrons that extends light-front holography by including finite mass quarks and a longitudinal confinement term. We propose that the model is suitable as an improved analytic approximation to QCD at a low resolution scale. We demonstrate that it preserves desired Lorentz symmetries and it produces improved agreement with the experimental mass spectroscopy and other properties of the light mesons. Importantly, the model also respects chiral symmetry and the Gell-Mann-Oakes-Renner relation.

   hep-phnucl-thPLB(2022)·50 citations
4. 04*

   Extraction of Proton Trace Anomaly Energy from Near-Threshold $\varphi$ and $J/\psi$ photo-productions

   Wei Kou🇨🇳 · Rong Wang🇨🇳 · Xurong Chen🇨🇳

   The trace anomalous energy contribution to the proton mass is a very important topic in non-perturbative QCD and hadron physics. In experiments, it is under the hot discussions on how to measure the trace anomalous energy.The QCD interpretation of proton trace anomaly is still not clear.To connect the theory with the experiment,we extract the trace anomaly by analyzing the near-threshold photo-production data of $\varphi$ and J/$\psi$ vector mesons. Based on the vector-meson-dominance model and QCD Van der Waals representation, we find that the percentage of trace anomaly in the proton mass ranges from $16\%$ to $24\%$, which is of similar order of magnitude as the 23$\%$ given by Lattice QCD. We also provide the approximate magnitudes of the systematic uncertainties of the extracted results from the model assumptions as well as the data fitting procedures. We give relative statistical uncertainties of 17.2$\%$, 17.7$\%$, 3.6$\%$, and 8.2$\%$, total relative systematic uncertainties of 21.4$\%$, 54.2$\%$, 37.2$\%$, and 25.7$\%$, for the analyses of the GlueX, LEPS, CLAS, and SAPHIR data, respectively. We argue that the near-threshold ${\rm Y}$ photo-production experiments are more beneficial for the measurement of trace anomaly in proton mass in the future.

   hep-phEPJA(2022)·23 citations
5. 05*

   One-loop form factors for $H\to {\gamma }^{\ast }{\gamma }^{\ast }$ in $R_{\xi }$ gauge

   Khiem Hong Phan🇻🇳 · Dzung Tri Tran🇻🇳

   In this paper, we present general one-loop form factors for $H\to {\gamma }^{\ast }{\gamma }^{\ast }$ in $R_{\xi }$ gauge, considering all cases of two on-shell, one on-shell and two off-shell for final photons. The calculations are performed in standard model and in arbitrary beyond the standard models which charged scalar particles may be exchanged in one-loop diagrams. Analytic results for the form factors are shown in general forms which are expressed in terms of the Passarino-Veltman functions. We also confirm the results in previous computations which are available for the case of two on-shell photons. The $\xi$-independent of the result is also discussed. We find that numerical results are good stability with varying $\xi =0,1$ and $\xi \to \infty$.

   hep-phCommun.in Phys.(2022)·1 citation
6. 06*

   A comparative study of type-II, inverse and linear seesaw mechanisms with $A_4$ flavour symmetry

   Maibam Ricky Devi🇮🇳 · Kalpana Bora🇮🇳

   We present a comparative analysis of neutrino models based on a broad class of low scale seesaw mechanisms, viz., type II, inverse (ISS) and linear seesaw (LSS) mechanisms that are used to realize the tiny masses of neutrino. In particular, we present their lagrangians with respective particle content. We incorporate $A_4$ flavour symmetry into our models to investigate the light neutrino masses and mixings and flavour structure as well. Apart from it, symmetries like $U(1{)}_X$, $Z_4$ and $Z_5$ to make the models viable are also used. Recent global fit values of neutrino oscillation parameters are used to find the unknown neutrino oscillation parameters such as the lightest neutrino mass and CPV phases (Dirac and Majorana). These unknown parameters can be found by solving a set of simultaneous equations obtained by using $A_4$ product rules in the Lagrangian for different VEV alignments of the triplet flavon field. Finally these data of unknown neutrino oscillation parameters are used to study cLFV (Charged lepton flavour violation) decay $\mu \to e+\gamma$ and is constrained using their latest bounds and sensitivities. Though we have constructed the models for all type II, ISS and LSS models for the sake of comparison, we focus on computation in LSS in this work. Computations are done up to the tolerance level $<10^{-5}$.

   hep-ph5 citations
7. 07*

   Analytical asymptotics for hard diffraction

   Anh Dung Le🇫🇷 · Alfred H. Mueller🇺🇸 · Stéphane Munier🇫🇷

   We show that the cross section for diffractive dissociation of a small onium off a large nucleus at total rapidity $Y$ and requiring a minimum rapidity gap $Y_{\text{gap}}$ can be identified, in a well-defined parametric limit, with a simple classical observable on the stochastic process representing the evolution of the state of the onium, as its rapidity increases, in the form of color dipole branchings: It formally coincides with twice the probability that an even number of these dipoles effectively participate in the scattering, when viewed in a frame in which the onium is evolved to the rapidity $Y-Y_{\text{gap}}$. Consequently, finding asymptotic solutions to the Kovchegov-Levin equation, which rules the $Y$-dependence of the diffractive cross section, boils down to solving a probabilistic problem. Such a formulation authorizes the derivation of a parameter-free analytical expression for the gap distribution. Interestingly enough, events in which many dipoles interact simultaneously play an important role, since the distribution of the number $k$ of dipoles participating in the interaction turns out to be proportional to $1/[k(k-1)]$.

   hep-phPRD(2021)·16 citations
8. 08*

   Relativistic spin sum rules and the role of the pivot

   Cédric Lorcé (Ecole Polytechnique, CPHT)🇫🇷

   Spin sum rules depend on the choice of a pivot, i.e. the point about which the angular momentun is defined, usually identified with the center of the nucleon. The latter is however not unique in a relativistic theory and has led to apparently contradictory results in the literature. Using the recently developed phase-space approach, we compute for the first time the contribution associated with the motion of the center of the nucleon, and we derive a general spin sum rule which reduces to established results after appropriate choices for the pivot and the spin component.

   hep-phnucl-thEPJC(2021)·24 citations
9. 09*

   Coherence of oscillations in matter and supernova neutrinos

   Yago P. Porto-Silva🇧🇷 · Alexei Yu. Smirnov🇩🇪

   We study the propagation coherence for neutrino oscillations in media with different density profiles. For each profile, we find the dependence of the coherence length, $L_{coh}$, on neutrino energy and address the issue of correspondence of results in the distance and energy-momentum representations. The key new feature in matter is existence of energy ranges with enhanced coherence around the energies $E_0$ of "infinite coherence" at which $L_{coh}\to \infty$. In the configuration space, the infinite coherence corresponds to equality of the (effective) group velocities of the eigenstates. In constant density medium, there is a unique $E_0$, which coincides with the MSW resonance energy of oscillations of mass states and is close to the MSW resonance energy of flavor states. In the case of massless neutrinos or negligible masses in a very dense medium the coherence persists continuously. In the adiabatic case, the infinite coherence is realized for periodic density change. Adiabaticity violation changes the shape factors of the wave packets (WPs) and leads to their spread. In a medium with sharp density changes (jumps), splitting of the eigenstates occurs at crossing of each jump. We study the increase of the coherence length in a single jump and periodic density jumps - castle-wall (CW) profiles. For the CW profile, there are several $E_0$ corresponding to parametric resonances. We outlined applications of the results for supernova neutrinos. In particular, we show that coherence between two shock wave fronts leads to observable oscillation effects, and our analysis suggests that the decoherence can be irrelevant for flavor transformations in the central parts of collapsing stars.

   hep-phastro-ph.HEhep-exJCAP(2021)·8 citations
10. 10*

    Probing $L_{\mu }-L_{\tau }$ models with CE$\nu$NS: A new look at the combined COHERENT CsI and Ar data

    Heerak Banerjee🇮🇳 · Bhaskar Dutta🇺🇸 · Sourov Roy🇮🇳

    The minimal gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ model has long been known to be able to explain the tension between the theoretical and experimental values of the muon magnetic moment. It has been explored and tested extensively, pushing the viable parameter space into a very tight corner. Further, embedding the $U(1{)}_{L_{\mu }-L_{\tau }}$ model in a supersymmetric (SUSY) framework has been shown to relax some of these constraints and has recently been shown to explain the electron anomalous magnetic moment as well. In this model, the logarithm of the mass ratio of third to second generation (s)leptons control the non-negligible kinetic mixing and may crucially alter many of the constraints. We confront both the non-SUSY and SUSY versions of this class of models with the CsI(2017), the recently released CENNS10 data from the liquid Argon detector as well as the updated CsI(2020) data of the COHERENT experiment. We use the recoil energy and timing binned data from CsI(2017) and the energy, time, and Pulse Shape Discriminator binned data from CENNS10 to find estimates for the model parameters in a likelihood maximization test. We also show updated exclusions using all of the above data from the COHERENT Collaboration, as well as projected exclusions from the ongoing Coherent CAPTAIN-Mills experiment. The $(g-2{)}_{\mu }$ favored values of the $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge coupling that are still unconstrained overlap with the estimates from COHERENT data within $1\sigma$. The combined COHERENT data is found to prefer the presence of the $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge boson over the Standard Model at $\sim 1.4\sigma$. The global minima of a chi-square deviation function using CsI(2020) as well as CENNS10 total counts has significant overlap with the $(g-2{)}_{\mu }$ favored parameter space in the context of the SUSY and non-SUSY $L_{\mu }-L_{\tau }$ models with a mediator mass in the $20-100$ MeV range.

    hep-phhep-exPRD(2021)·32 citations
11. 11*

    Model-independent searches for new physics in multi-body invariant masses

    S.V. Chekanov🇺🇸 · S. Darmora🇺🇸 · W. Islam🇺🇸 · C.E.M. Wagner🇺🇸 · J. Zhang🇺🇸

    Model-independent searches for physics beyond the Standard Model typically focus on invariant masses of two objects (jets, leptons or photons). In this study we explore opportunities for similar model-agnostic searches in multi-body invariant masses. In particular, we focus on the situations when new physics can be observed in a model-independent way in three- and four-body invariant masses of jets and leptons. Such searches may have good prospects in finding new physics in the situations when two-body invariant masses, that have been extensively explored at collider experiments in the past, cannot provide sufficient signatures for experimental observations.

    hep-phUniverse(2021)·6 citations
12. 12*

    Lepton-Charge and Forward-Backward Asymmetries in Drell-Yan Processes for Precision Electroweak Measurements and New Physics Searches

    Juri Fiaschi🇬🇧 · Francesco Giuli🇨🇭 · Francesco Hautmann🇧🇪 · Stefano Moretti🇬🇧

    Precision determinations of Standard Model (SM) Electro-Weak (EW) parameters at the Large Hadron Collider (LHC) are dominated by uncertainties due to Parton Distribution Functions (PDFs). Reweighting and profiling techniques are routinely employed to treat this. We explore approaches based on combining measurements of charged current and neutral current Drell-Yan (DY) asymmetries to improve PDF uncertainties. We present the results of a numerical analysis performed with the open-source platform xFitter. PDF uncertainties are examined for lepton-charge and forward-backward asymmetries in regions of transverse and invariant masses near the vector-boson peak, based on LHC Run III and HL-LHC luminosity scenarios. We discuss the complementarity of the asymmetries in reducing PDF uncertainties in observables relevant to both SM and Beyond the SM (BSM) physics.

    hep-phNPB(2021)·23 citations
13. 13*

    Determining the helicity structure of the nucleon at the Electron Ion Collider in China

    Daniele Paolo Anderle🇨🇳 · Tie-Jiun Hou🇨🇳 · Hongxi Xing🇨🇳 · Mengshi Yan🇨🇳 · C.-P. Yuan🇺🇸 · Yuxiang Zhao🇨🇳

    Understanding how sea quarks behave inside a nucleon is one of the most important physics goals of the proposed Electron-Ion Collider in China (EicC), which is designed to have 3.5 GeV polarized electron beam (80% polarization) colliding with 20 GeV polarized proton beam (70% polarization) at instantaneous luminosity of $2\times 10^{33}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$. A specific topic at EicC is to understand the polarization of individual quarks inside a longitudinally polarized nucleon. The potential of various future EicC data, including the inclusive and semi-inclusive deep inelastic scattering data from both doubly polarized electron-proton and electron-${}^3\mathrm{He}$ collisions, to reduce the uncertainties of parton helicity distributions is explored at the next-to-leading order in QCD, using the Error PDF Updating Method Package ({\sc ePump}) which is based on the Hessian profiling method. We show that the semi-inclusive data are well able to provide good separation between flavour distributions, and to constrain their uncertainties in the $x>0.005$ region, especially when electron-${}^3\mathrm{He}$ collisions, acting as effective electron-neutron collisions, are taken into account. To enable this study, we have generated a Hessian representation of the DSSV14 set of PDF replicas, named DSSV14H PDFs.

    hep-phhep-exJHEP(2021)·9 citations
14. 14*

    Exploiting dijet resonance searches for flavor physics

    Marzia Bordone🇩🇪 · Admir Greljo🇨🇭 · David Marzocca🇮🇹

    In this work, we reinterpret ATLAS and CMS dijet resonance searches to set robust constraints on all hypothetical tree-level scalar and vector mediators with masses up to 5 TeV, assuming a diquark or a quark-antiquark coupling with an arbitrary flavor composition. To illustrate the application of these general results, we quantify the permissible size of new physics in ${\bar{B}}_q\to D_q^{(\ast )+}\{\pi ,K\}$ consistent with the absence of signal in dijet resonance searches. Along the way, we perform a full SMEFT analysis of the aforementioned non-leptonic $B$ meson decays at leading-order in ${\alpha }_s$. Our findings uncover a pressing tension between the new physics explanations of recently reported anomalies in these decays and the dijet resonant searches. The high-$p_T$ constraints are crucial to drain the parameter space consistent with the low-$p_T$ flavor physics data.

    hep-phJHEP(2021)·54 citations
15. 15*

    Flavor Mixing of Quarks and a New Texture

    Harald Fritzsch🇩🇪

    We discuss a new mass matrix with specific texture zeros for the quarks. The three flavor mixing angles for the quarks are functions of the quark masses and can be calculated. The following ratios among CKM matrix elements are given by ratios of quark masses: |Vtd/Vts| ' q md /ms and |Vub/Vcb| ' p mu/mc . Also we can calculate two CKM matrix elements: |Vcb| ' |Vts| ' 2 (ms/mb ). This relation as well as the relation |Vtd/Vts| ' q md /ms are in good agreement with the experimental data. There is a problem with the relation |Vub/Vcb| ' p mu/mc , probably due to wrong estimates of the quark masses mu and m

    hep-phMod.Phys.Lett.A(2021)·4 citations
16. 16*

    Production and signatures of multi-flavour dark matter scenarios with t-channel mediators

    Johannes Herms🇩🇪 · Alejandro Ibarra🇩🇪

    We investigate the phenomenology of a dark matter scenario containing two generations of the dark matter particle, differing only by their mass and their couplings to the other particles, akin to the quark and lepton sectors of the Standard Model. For concreteness, we consider the case where the two dark matter generations are Majorana fermions that couple to a right-handed lepton and a scalar mediator through Yukawa couplings. We identify different production regimes in the multi-flavor dark matter scenario and we argue that in some parts of the parameter space the heavier generation can play a pivotal role in generating the correct dark matter abundance. In these regions, the strength of the dark matter coupling to the Standard Model can be much larger than in the single-flavored dark matter scenario. Correspondingly the indirect and direct detection signals can be significantly boosted. We also comment on the signatures of the model from the decay of the heavier dark matter generation into the lighter.

    hep-phJCAP(2021)·13 citations
17. 17*

    Shear-induced spin polarization in heavy-ion collisions

    Baochi Fu🇨🇳 · Shuai Y. F. Liu🇨🇳 · Longgang Pang🇨🇳 · Huichao Song🇨🇳 · Yi Yin🇨🇳

    We study the spin polarization generated by the hydrodynamic gradients. In addition to the widely studied thermal vorticity effects, we identify an undiscovered contribution from the fluid shear. This shear-induced polarization (SIP) can be viewed as the fluid analog of strain-induced polarization observed in elastic and nematic materials. We obtain the explicit expression for SIP using the quantum kinetic equation and linear response theory. Based on a realistic hydrodynamic model, we compute the differential spin polarization along both the beam direction $\hat{z}$ and the out-plane direction $\hat{y}$ in non-central heavy-ion collisions at $\sqrt{s_{NN}}=200$ GeV, including both SIP and thermal vorticity effects. We find that SIP contribution always shows the same azimuthal angle dependence as experimental data and competes with thermal vorticity effects. In the scenario that $\Lambda$ inherits and memorizes the spin polarization of strange quark, SIP wins the competition, and the resulting azimuthal angle dependent spin polarization $P_y$ and $P_z$ agrees qualitatively with the experimental data.

    hep-phnucl-thPRL(2021)·238 citations
18. 18*

    Exploring theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions

    Cheng Chiu🇺🇸 · Chun Shen🇺🇸

    We explore theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions by examining the full non-linear causality conditions and quantifying the second-order transport coefficients' role on flow observables. The causality conditions impose physical constraints on the maximum allowed values of inverse Reynolds numbers during the hydrodynamic evolution. Including additional second-order gradient terms in the Denicol-Niemi-Molnár-Rischke (DNMR) theory significantly shrinks the casual regions compared to those in the Israel-Stewart hydrodynamics. For Au+Au collisions, we find the variations of flow observables are small with and without imposing the necessary causality conditions, suggesting a robust extraction of the Quark-Gluon Plasma's transport coefficients in previous model-to-data comparisons. However, sizable sensitivity is present in small p+Au collisions, which poses challenges to study the small systems' collectivity.

    ↳ nucl-thhep-phnucl-exPRC(2021)·53 citations
19. 19*

    Stochastic computation of $g-2$ in QED

    Ryuichiro Kitano🇯🇵 · Hiromasa Takaura🇯🇵 · Shoji Hashimoto🇯🇵

    We perform a numerical computation of the anomalous magnetic moment ($g-2$) of the electron in QED by using the stochastic perturbation theory. Formulating QED on the lattice, we develop a method to calculate the coefficients of the perturbative series of $g-2$ without the use of the Feynman diagrams. We demonstrate the feasibility of the method by performing a computation up to the ${\alpha }^3$ order and compare with the known results. This program provides us with a totally independent check of the results obtained by the Feynman diagrams and will be useful for the estimations of not-yet-calculated higher order values. This work provides an example of the application of the numerical stochastic perturbation theory to physical quantities, for which the external states have to be taken on-shell.

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

    Quarkyonic stars with isospin-flavor asymmetry

    J. Margueron🇫🇷 · H. Hansen🇫🇷 · P. Proust🇫🇷 · G. Chanfray🇫🇷

    We suggest an extension to isospin asymmetric matter of the quarkyonic model from McLerran and Reddy. This extension allows us to construct the $\beta$-equilibrium between quarks, nucleons and leptons. The concept of the quarkyonic matter originates from the large number of color limit for which nucleons are the correct degrees of freedom near the Fermi surface -- reflecting the confining forces -- while deep inside the Fermi sea quarks naturally appear. In isospin asymmetric matter, we suggest that this new concept can be implemented within a global isoscalar relation between the shell gaps differentiating the nucleon and the quark sectors. In addition, we impose the conservation of the isospin-flavor asymmetry in the nucleon and the quark phases. Within this model, several quarkyonic stars are constructed on top of the SLy4 model for the nucleon sector, producing a bump in the sound speed, which implies that quarkyonic stars are systematically bigger and have a larger maximum mass than the associated neutron stars. They also predict lower proton fraction at $\beta$-equilibrium, which potentially quenches fast cooling in massive compact stars.

    ↳ nucl-thastro-ph.HEhep-phPRC(2021)·54 citations
21. 21*

    Hierarchical structure of physical Yukawa couplings from matter field Kähler metric

    Keiya Ishiguro🇯🇵 · Tatsuo Kobayashi🇯🇵 · Hajime Otsuka🇯🇵

    We study the impacts of matter field Kähler metric on physical Yukawa couplings in string compactifications. Since the Kähler metric is non-trivial in general, the kinetic mixing of matter fields opens a new avenue for realizing a hierarchical structure of physical Yukawa couplings, even when holomorphic Yukawa couplings have the trivial structure. The hierarchical Yukawa couplings are demonstrated by couplings of pure untwisted modes on toroidal orbifolds and their resolutions in the context of heterotic string theory with standard embedding. Also, we study the hierarchical couplings among untwisted and twisted modes on resolved orbifolds.

    ↳ hep-thhep-phJHEP(2021)·13 citations
22. 22*

    Half-integer anomalous currents in 2D materials from a QFT viewpoint

    D. Dudal🇧🇪 · F. Matusalem🇧🇷 · A. J. Mizher🇧🇷 · A. R. Rocha🇧🇷 · C. Villavicencio🇨🇱

    Charge carriers in Dirac/Weyl semi-metals exhibit a relativistic-like behavior. In this work we propose a novel type of intrinsic half-integer Quantum Hall effect in 2D materials, thereby also offering a topological protection mechanism for the current. Its existence is rooted in the 2D parity anomaly, without any need for a perpendicular magnetic field. We conjecture that it may occur in disturbed honeycomb lattices where both spin degeneracy and time reversal symmetry are broken. These configurations harbor two distinct gap-opening mechanisms that, when occurring simultaneously, drive slightly different gaps in each valley, causing a net anomalous conductivity when the chemical potential is tuned to be between the distinct gaps. Some examples of promising material setups that fulfill the prerequisites of our proposal are also listed to motivate looking for the effect at the numerical and experimental level.

    ↳ cond-mat.mes-hallhep-phhep-thnucl-thSci.Rep.(2022)·11 citations
23. 23*

    Generation of polarized positron beams via collisions of ultrarelativistic electron beams

    Huai-Hang Song🇨🇳 · Wei-Min Wang🇨🇳 · Yu-Tong Li🇨🇳

    A novel scheme is proposed for generating a polarized positron beam via multiphoton Breit-Wheeler process during the collision of a 10 GeV, pC seeding electron beam with the other 1 GeV, nC driving electron beam. The driving beam provides the strong self-generated field, and a suitable transverse deviation distance between two beams enables the field experienced by the seeding beam to be unipolar, which is crucial for realizing the positron polarization. We employ the particle simulation with a Monte-Carlo method to calculate the spin- and polarization-resolved photon emission and electron-positron pair production in the local constant field approximation. Our simulation results show that a highly polarized positron beam with polarization above $40\%$ can be generated in several femtoseconds, which is robust with respect to parameters of two electron beams. Based on an analysis of the influence of $\gamma$-photon polarization on the polarized pair production, we find that a polarized seeding beam of the proper initial polarization can further improve the positron polarization to $60\%$.

    ↳ physics.acc-phhep-phphysics.plasm-phPRResearch(2021)·8 citations
24. 24*

    The Gravitino Swampland Conjecture

    Edward W. Kolb🇺🇸 · Andrew J. Long🇺🇸 · Evan McDonough🇺🇸

    We extend the swampland from effective field theories (EFTs) inconsistent with quantum gravity to EFTs inconsistent with quantum supergravity. This enlarges the swampland to include EFTs that become inconsistent when the gravitino is quantized. We propose the Gravitino Swampland Conjecture: the gravitino sound speed must be non-vanishing in all EFTs that are low energy limits of quantum supergravity. This seemingly simple statement has important consequences for both theories and observations. The conjecture is consistent with and supported by the KKLT and LVS scenarios for moduli stabilization in string theory.

    ↳ hep-thastro-ph.COgr-qchep-phPRL(2021)·57 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.