Fri·Jun 25, 2021Friday·June 25, 2021

1. 01*

   Cosmic Birefringence and Electroweak Axion Dark Energy

   Gongjun Choi🇨🇳 · Weikang Lin🇨🇳 · Luca Visinelli🇨🇳 · Tsutomu T. Yanagida🇨🇳

   Taking the recently reported non-zero rotation angle of the cosmic microwave background (CMB) linear polarization $\beta =0.35\pm 0.14\mathrm{deg}$ as the hint for a pseudo Nambu-Goldstone boson quintessence dark energy (DE), we study the electroweak (EW) axion quintessence DE model where the axion mass is generated by the EW instantons. We find that the observed value of $\beta$ implies a non-trivial $U(1)$ electromagnetic anomaly coefficient ($c_{\gamma }$), once the current constraint on the DE equation of state is also taken into account. With the aid of the hypothetical high energy structure of the model inspired by the experimentally inferred $c_{\gamma }$, the model is shown to be able to make prediction for the current equation of state ($w_{\mathrm{DE},0}$) of the quintessence DE. This is expected to make our scenario distinguishable in comparison with the cosmological constant ($w=-1$) and testable in future when the error in the future measurement of $w_{\mathrm{DE},0}$ is reduced to $\mathcal{O}(1)\%$ level ($\delta w=\mathcal{O}(10^{-2})$).

   hep-phastro-ph.COPRD(2021)·82 citations
2. 02*

   Exploring new possibilities to discover a light pseudo-scalar at LHCb

   Diogo Buarque Franzosi🇸🇪 · Giacomo Cacciapaglia🇫🇷 · Xabier Cid Vidal🇪🇸 · Gabriele Ferretti🇸🇪 · Thomas Flacke🇰🇷 · Carlos Vázquez Sierra🇨🇭

   We study the possibility of observing a light pseudo-scalar $a$ at LHCb. We target the mass region $1\lesssim m_a\lesssim 60$ GeV and various decay channels, some of which have never been considered before: muon pairs, tau pairs, $D$ meson pairs, and di-photon. We interpret the results in the context of models of 4D Composite Higgs and Partial Compositeness in particular.

   hep-phhep-exEPJC(2022)·31 citations
3. 03*

   Cubic color charge correlator in a proton made of three quarks and a gluon

   Adrian Dumitru🇺🇸 · Heikki Mäntysaari🇫🇮 · Risto Paatelainen🇫🇮

   The three point correlation function of color charge densities is evaluated explicitly in light cone gauge for a proton on the light cone. This includes both $C$-conjugation even and odd contributions. We account for perturbative corrections to the three-quark light cone wave function due to the emission of an internal gluon which is not required to be soft. We verify the Ward identity as well as the cancellation of UV divergences in the sum of all diagrams so that the correlator is independent of the renormalization scale. It does, however, exhibit the well known soft and collinear singularities. The expressions derived here provide the $C$-odd contribution to the initial conditions for high-energy evolution of the dipole scattering amplitude to small $x$. Finally, we also present a numerical model estimate of the impact parameter dependence of quantum color charge three-point correlations in the proton at moderately small $x$.

   hep-phPRD(2022)·15 citations
4. 04*

   $R(K^{(\ast )})$ with vector unparticles

   Jong-Phil Lee🇰🇷

   We analyze the unparticle effects on the lepton flavor universality violating ratios in $b\to s$ transition, $R(K^{(\ast )})$. We concentrate on the vector unparticles which contribute to the relevant Wilson coefficients $C_{9,10}$. New effects appear in the form of some powers of the momentum transfer squared, which is a different feature from other new physics models like leptoquarks or $Z^{\prime }$. Constraints from $B_s$-${\bar{B}}_s$ mixing, $B_s\to {\mu }^{+}{\mu }^{-}$, and the electron/muon anomalous magnetic moments are considered. It is found that the vector unparticles successfully explain $R(K^{(\ast )})$ with moderate values of model parameters.

   hep-ph7 citations
5. 05*

   Higher-order corrections to exclusive heavy vector meson production

   Tuomas Lappi🇫🇮 · Heikki Mäntysaari🇫🇮 · Jani Penttala🇫🇮

   We present results for higher-order corrections to exclusive $\mathrm{J}/\psi$ production. This includes the first relativistic correction of order $v^2$ in quark velocity, and next-to-leading order corrections in ${\alpha }_s$ for longitudinally polarized production. The relativistic corrections are found to be important for a good description of the HERA data, especially at small values of the photon virtuality. The next-to-leading order results for longitudinal production are evaluated numerically. We also demonstrate how the vector meson production provides complementary information to the structure functions for extracting the initial condition for the small-$x$ evolution of the dipole-proton scattering amplitude.

   hep-phnucl-thSciPost Phys.Proc.(2022)·8 citations
6. 06*

   Investigating the structure of gluon fluctuations in the proton with incoherent diffraction at HERA

   Arjun Kumar🇮🇳 · Tobias Toll🇮🇳

   Impact parameter dependent dipole models are ideal tools for investigating the spatial structure of the proton. We investigate the incoherent $ep$ cross section in exclusive $J/\psi$ photoproduction as measured by HERA, and find that as $|t|$ increases, the models need several levels of the substructure of gluon density fluctuations in order to describe the measured data well. In lieu of a perturbative description, we add this substructure by hand. This substructure is modelled as hotspots within hotspots. This enables us to describe measurements for $|t|>1$~GeV${}^2$, which is necessary for describing any observable which integrates over the $t$-spectrum, such as the rapidity or $W_{\gamma p}$. We find that three levels of proton substructure are adequate for a good description of all available $ep$ data up to $|t|=30$GeV${}^2$. We note that the gluonic density fluctuation structure follows a scaling behaviour, such that the logarithms of the number of hotspots and their size fall on a line, effectively reducing the available parameter space of the model. Our findings systematically constrain and provide a benchmark for the development of a perturbative model of spatial gluon fluctuations in nucleons.

   hep-phEPJC(2022)·27 citations
7. 07*

   Prospects on searches for baryonic Dark Matter produced in $b$-hadron decays at LHCb

   Alexandre Brea Rodríguez🇪🇸 · Veronika Chobanova🇪🇸 · Xabier Cid Vidal🇪🇸 · Saúl López Soliño🇪🇸 · Diego Martínez Santos🇪🇸 · Titus Mombächer🇪🇸 · Claire Prouvé🇪🇸 · Emilio Xosé Rodríguez Fernández🇪🇸 · Carlos Vázquez Sierra🇨🇭

   A model that can simultaneously explain Dark Matter relic density and the apparent matter anti-matter imbalance of the universe has been recently proposed. The model requires $b$-hadron branching fractions to Dark Matter at the per mille level. The $b$-hadrons decay to a dark sector baryon, ${\psi }_{\mathrm{DS}}$, which has a mass in the region $940$ MeV/c${}^2\le m({\psi }_{\mathrm{DS}})\le 4430$ MeV/c${}^2$. In this paper, we discuss the sensitivity of the LHCb experiment to search for this dark baryon, covering different types of topology and giving prospects for Runs 3 and 4 of the LHC, as well as for the proposed Phase-II Upgrade. We show that the LHCb experiment can cover the entire mass range of the hypothetical dark baryon.

   hep-phhep-exEPJC(2021)·26 citations
8. 08*

   $tW$ and $t{Z}^{\prime }$ production at hadron colliders

   Nikolaos Kidonakis🇺🇸 · Marco Guzzi🇺🇸 · Nodoka Yamanaka🇺🇸

   We present theoretical results with soft-gluon corrections for two separate processes: (1) the production of a single top quark in association with a $W$ boson in the Standard Model; and (2) the production of a single top quark in association with a heavy $Z^{\prime }$ boson in new physics models with or without anomalous couplings. We show that the higher-order corrections from soft-gluon emission are dominant for a wide range of collider energies. Results are shown for the total cross sections and top-quark transverse-momentum and rapidity distributions for $tW$ and $t{Z}^{\prime }$ production at LHC and future collider energies up to 100 TeV. The uncertainties from scale dependence and parton distribution functions are also analyzed.

   hep-phSciPost Phys.Proc.(2022)·0 citations
9. 09*

   Peccei-Quinn symmetry with residual symmetries

   Pei-Hong Gu🇨🇳

   So far the null results from axion searches have enforced a huge hierarchy between the Peccei-Quinn and electroweak symmetry breaking scales. Then the inevitable Higgs portal poses a large fine tuning on the standard model Higgs scalar. Now we find if the Peccei-Quinn global symmetry has a set of residually discrete symmetries, these global and discrete symmetries can achieve a chain breaking at low scales such as the accessible TeV scale. This novel mechanism can accommodate some new phenomena including a sizable coupling of the standard model Higgs boson to the axion.

   hep-ph1 citation
10. 10*

    Two-Loop Four-Fermion Scattering Amplitude in QED

    R. Bonciani🇮🇹 · A. Broggio🇮🇹 · S. Di Vita🇮🇹 · A. Ferroglia🇺🇸 · M. K. Mandal🇮🇹 · P. Mastrolia🇮🇹 · L. Mattiazzi🇮🇹 · A. Primo🇨🇭 · J. Ronca🇮🇹 · U. Schubert🇺🇸 · W. J. Torres Bobadilla🇩🇪 · F. Tramontano🇮🇹

    We present the analytic evaluation of the two-loop corrections to the amplitude for the scattering of four fermions in Quantum Electrodynamics, $f^{-}+f^{+}+F^{-}+F^{+}\to 0$, with $f$ and $F$ representing a massless and a massive lepton, respectively. Dimensional regularization is employed to evaluate the loop integrals. Ultraviolet divergences are removed by renormalizing the coupling constant in the $\overline{\text{MS}}$-scheme, and the lepton mass as well as the external fields in the on-shell scheme. The analytic result for the renormalized amplitude is expressed as Laurent series around $d=4$ space-time dimensions, and contains Generalized Polylogarithms with up to weight four. The structure of the residual infrared divergences of the virtual amplitude is in agreement with the prediction of the Soft Collinear Effective Theory. Our analytic results are an essential ingredient for the computation of the scattering cross section for massive fermion-pair production in massless fermion-pair annihilation, i.e. $f^{-}{f}^{+}\to F^{-}{F}^{+}$, and crossing related processes such as the elastic scattering $fF\to fF$, with up to Next-to-Next to Leading Order accuracy.

    hep-phhep-thPRL(2022)·49 citations
11. 11*

    Short-distance constraints for the longitudinal component of the hadronic light-by-light amplitude: an update

    Gilberto Colangelo🇨🇭 · Franziska Hagelstein🇨🇭 · Martin Hoferichter🇨🇭 · Laetitia Laub🇨🇭 · Peter Stoffer🇦🇹

    We reassess the impact of short-distance constraints for the longitudinal component of the hadronic light-by-light amplitude on the anomalous magnetic moment of the muon, $a_{\mu }=(g-2{)}_{\mu }/2$, by comparing different solutions that have recently appeared in the literature. In particular, we analyze the relevance of the exact axial anomaly and its impact on $a_{\mu }$ and conclude that it remains rather limited. We show that all recently proposed solutions agree well within uncertainties on the numerical estimate of the impact of short-distance constraints on $a_{\mu }$, despite differences in the concrete implementation. We also take into account the recently calculated perturbative corrections to the massless quark loop to update our estimate and outline the path towards future improvements.

    hep-phhep-latnucl-thEPJC(2021)·73 citations
12. 12*

    Design and engineering of a simplified workflow execution for the MG5aMC event generator on GPUs and vector CPUs

    Andrea Valassi🇨🇭 · Stefan Roiser🇨🇭 · Olivier Mattelaer🇧🇪 · Stephan Hageboeck🇨🇭

    Physics event generators are essential components of the data analysis software chain of high energy physics experiments, and important consumers of their CPU resources. Improving the software performance of these packages on modern hardware architectures, such as those deployed at HPC centers, is essential in view of the upcoming HL-LHC physics programme. In this paper, we describe an ongoing activity to reengineer the Madgraph5_aMC@NLO physics event generator, primarily to port it and allow its efficient execution on GPUs, but also to modernize it and optimize its performance on vector CPUs. We describe the motivation, engineering process and software architecture design of our developments, as well as the current challenges and future directions for this project. This paper is based on our submission to vCHEP2021 in March 2021,complemented with a few preliminary results that we presented during the conference. Further details and updated results will be given in later publications.

    ↳ physics.comp-phcs.SEhep-exhep-phEPJ Web Conf.(2021)·34 citations
13. 13*

    Deconstructing finite temperature pure gauge theory

    Herbert Neuberger🇺🇸

    A deconstructed finite temperature gauge theory has the Euclidean time direction kept discrete and finite. The ultraviolet behavior is that of one dimension less than at zero temperature. One can add to the action a gauge invariant term dependent on Polyakov loops, without worrying about nonlocality. The deformation of Ünsal and Yaffe is best analyzed in this framework. It is shown that turning it on causes a dramatic change in the Hilbert space on which the transfer matrix in the temperature direction acts. The undeformed Hilbert space is everywhere a gauge singlet while the deformed one includes all states transforming locally, anywhere, under any SU(N)/Z(N) irreducible representation. Implications of this in the context of large N reduction are discussed.

    ↳ hep-thhep-lathep-ph1 citation
14. 14*

    Relativistic kinetic approach to light nuclei production in high-energy nuclear collisions

    Kai-Jia Sun🇺🇸 · Rui Wang🇨🇳 · Che Ming Ko🇺🇸 · Yu-Gang Ma🇨🇳 · Chun Shen🇺🇸

    Understanding the production mechanism of light (anti-)nuclei in high-energy nuclear collisions and cosmic rays has been a long-standing problem in nuclear physics. In the present study, we develop a stochastic method to solve the relativistic kinetic equations for light nuclei production from many-body reactions with the inclusion of their finite sizes. The present approach gives an excellent description of the deuteron and helium-3 data from central Au+Au (Pb+Pb) collisions at $\sqrt{s_{\mathrm{NN}}}$ $=$ $200\mathrm{GeV}$ ($2.76\mathrm{TeV}$). It can also naturally explain their suppressed production in $pp$ collisions at 7 TeV as a result of their finite sizes.

    ↳ nucl-thhep-ph30 citations
15. 15*

    Quantum Kinetic Equation for Fluids of Spin-1/2 Fermions

    Ö.F.Dayi🇹🇷 · E. Kilinçarslan🇹🇷

    Fluid of spin-1/2 fermions is represented by a complex scalar field and a four-vector field coupled both to the scalar and the Dirac fields. We present the underlying action and show that the resulting equations of motion are identical to the (hydrodynamic) Euler equations in the presence of Coriolis force. As a consequence of the gauge invariances of this action we established the quantum kinetic equation which takes account of noninertial properties of the fluid in the presence of electromagnetic fields. The equations of the field components of Wigner function in Clifford algebra basis are employed to construct new semiclassical covariant kinetic equations of the vector and axial-vector field components for massless as well as massive fermions. Nonrelativistic limit of the chiral kinetic equation is studied and shown that it generates a novel three-dimensional transport theory which does not depend on spatial variables explicitly and possesses a Coriolis force term. We demonstrated that the three-dimensional chiral transport equations are consistent with the chiral anomaly. For massive fermions the three-dimensional kinetic transport theory generated by the new covariant kinetic equations is established in small mass limit. It possesses the Coriolis force and the massless limit can be obtained directly.

    ↳ hep-thhep-phmath.APJHEP(2021)·6 citations
16. 16*

    Lattice QCD Study of Transverse-Momentum Dependent Soft Function

    Yuan Li🇨🇳 · Shi-Cheng Xia🇨🇳 · Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Xu Feng🇨🇳 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Chuan Liu🇨🇳 · Aurora Scapellato🇺🇸 · Fernanda Steffens🇩🇪 · Jacopo Tarello🇨🇾

    In this work, we perform a lattice QCD study of the intrinsic, rapidity-independent soft function within the framework of large momentum effective theory. The computation is carried out using a gauge ensemble of $N_f=2+1+1$ clover-improved twisted mass fermion. After applying an appropriate renormalization procedure and the removal of significant higher-twist contamination, we obtain the intrinsic soft function that is comparable to the one-loop perturbative result at large external momentum. The determination of the nonperturbative soft function from first principles is crucial to sharpen our understanding of the processes with small transverse momentum such as the Drell-Yan production and the semi-inclusive deep inelastic scattering. Additionally, we calculate the Collins-Soper evolution kernel using the quasi-transverse-momentum-dependent wave function as input.

    ↳ hep-lathep-phPRL(2022)·98 citations
17. 17*

    A Pedagogical Introduction to Holographic Hadrons

    Sophia K Domokos🇺🇸 · Robert Bell🇺🇸 · Trinh La🇺🇸 · Patrick Mazza🇺🇸

    String theory's holographic QCD duality makes predictions for hadron physics by building models that live in five-dimensional (5D) curved space. In this pedagogical note, we explain how finding the hadron mass spectrum in these models amounts to finding the eigenvalues of a time-independent, one-dimensional Schroedinger equation. Changing the structure of the 5D curved space is equivalent to altering the potential in the Schroedinger equation, which in turn alters the hadron spectrum. We illustrate this concept with three holographic QCD models possessing exact analogs in basic quantum mechanics: the free particle, the infinite square well, and the harmonic oscillator. In addition to making aspects of holographic QCD accessible to undergraduates, this formulation can provide students with intuition for the meaning of curved space. This paper is intended primarily as a tool for researchers interested in involving early-stage undergraduates in research, but is also a suitable introduction to elements of holographic QCD for advanced undergraduate- and beginning graduate students with some knowledge of general relativity and classical field theory.

    ↳ hep-thhep-ph0 citations
18. 18*

    Cosmological structure formation in scalar field dark matter with repulsive self-interaction: The Incredible Shrinking Jeans Mass

    Paul R. Shapiro🇺🇸 · Taha Dawoodbhoy🇺🇸 · Tanja Rindler-Daller🇦🇹

    Scalar Field Dark Matter (SFDM) comprised of ultralight ($\gtrsim 10^{-22}$ eV) bosons is an alternative to standard, collisionless Cold Dark Matter (CDM) that is CDM-like on large scales but inhibits small-scale structure formation. As a Bose-Einstein condensate, its free-field ("fuzzy") limit (FDM) suppresses structure below the de Broglie wavelength, ${\lambda }_{\text{deB}}$, creating virialized haloes with central cores of radius $\sim {\lambda }_{\text{deB}}$, surrounded by CDM-like envelopes, and a halo mass function (HMF) with a sharp cut-off on small scales. With a strong enough repulsive self-interaction (SI), structure is inhibited, instead, below the Thomas-Fermi (TF) radius, $R_{\text{TF}}$ (the size of an SI-pressure-supported ($n=1$)-polytrope), when $R_{\text{TF}}>{\lambda }_{\text{deB}}$. Previously, we developed tools to describe SFDM dynamics on scales above ${\lambda }_{\text{deB}}$ and showed that SFDM-TF haloes formed by Jeans-unstable collapse from non-cosmological initial conditions have $R_{\text{TF}}$-sized cores, surrounded by CDM-like envelopes. Revisiting SFDM-TF in the cosmological context, we simulate halo formation by cosmological infall and collapse, and derive its transfer function from linear perturbation theory to produce cosmological initial conditions and predict statistical measures of structure formation, such as the HMF. Since FDM and SFDM-TF transfer functions both have small-scale cut-offs, we can align them to let observational constraints on FDM proxy for SFDM-TF, finding FDM with particle masses $1\lesssim m/(10^{-22}\text{ eV}/c^2)\lesssim 30$ corresponds to SFDM-TF with $10\gtrsim R_{\text{TF}}/(1\text{ pc})\gtrsim 1$, favoring sub-galactic (sub-kpc) core-size. The SFDM-TF HMF cuts off gradually, however, leaving more small-mass haloes: its Jeans mass shrinks so fast, scales filtered early can still recover and grow!

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2021)·40 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.