Mon·Jun 28, 2021Monday·June 28, 2021

1. 01*

   Probing the gluon tomography in photoproduction of di-pions

   Yoshikazu Hagiwara🇨🇳 · Cheng Zhang🇨🇳 · Jian Zhou🇨🇳 · Ya-jin Zhou🇨🇳

   A sizable $\cos 4\varphi$ azimuthal asymmetry in exclusive di-pion production near ${\rho }^0$ resonance peak in ultraperipheral heavy ion collisions recently has been reported by STAR collaboration. We show that both elliptic gluon Wigner distribution and final state soft photon radiation can give rise to this azimuthal asymmetry. The fact that the QED effect alone severely underestimates the observed asymmetry might signal the existence of the nontrivial correlation in quantum phase distribution of gluons.

   hep-phPRD(2021)·35 citations
2. 02*

   The role of colour flows in matrix element computations and Monte Carlo simulations

   Stefano Frixione🇮🇹 · Bryan R. Webber🇬🇧

   We discuss how colour flows can be used to simplify the computation of matrix elements, and in the context of parton shower Monte Carlos with accuracy beyond leading-colour. We show that, by systematically employing them, the results for tree-level matrix elements and their soft limits can be given in a closed form that does not require any colour algebra. The colour flows that we define are a natural generalization of those exploited by existing Monte Carlos; we construct their representations in terms of different but conceptually equivalent quantities, namely colour loops and dipole graphs, and examine how these objects may help to extend the accuracy of Monte Carlos through the inclusion of subleading-colour effects. We show how the results that we obtain can be used, with trivial modifications, in the context of QCD+QED simulations, since we are able to put the gluon and photon soft-radiation patterns on the same footing. We also comment on some peculiar properties of gluon-only colour flows, and their relationships with established results in the mathematics of permutations.

   hep-phJHEP(2021)·7 citations
3. 03*

   Goldstone Boson Scattering with a Light Composite Scalar

   T. Appelquist · R. C. Brower · K. K. Cushman · G. T. Fleming · A. Gasbarro · A. Hasenfratz · J. Ingoldby · X. Y. Jin · J. Kiskis · E. T. Neil · J. C. Osborn · C. Rebbi and 5 other authors

   The appearance of a light composite $0^{+}$ scalar resonance in nearly conformal gauge-fermion theories motivates further study of the low energy structure of these theories. To this end, we present a nonperturbative lattice calculation of s-wave scattering of Goldstone bosons in the maximal-isospin channel in SU(3) gauge theory with $N_f=8$ light, degenerate flavors. The scattering phase shift is measured both for different values of the underlying fermion mass and for different values of the scattering momentum. We examine the effect of a light flavor-singlet scalar (reported in earlier studies) on Goldstone boson scattering, employing a dilaton effective field theory (EFT) at the tree level. The EFT gives a good description of the scattering data, insofar as the magnitude of deviations between EFT and lattice data are no larger than the expected size of next-to-leading order corrections in the EFT.

   hep-phhep-latPRD(2022)·24 citations
4. 04*

   Chiral symmetry restoration and properties of Goldstone bosons at finite temperature

   Yin-Zhen Xu🇨🇳 · Si-Xue Qin🇨🇳 · Hong-Shi Zong🇨🇳

   We study chiral symmetry restoration by analyzing thermal properties of QCD's (pseudo-)Goldstone bosons, especially the pion. The meson properties are obtained from the spectral densities of mesonic imaginary-time correlation functions. To obtain the correlation functions, we solve the Dyson-Schwinger equations and the inhomogeneous Bethe-Salpeter equations in the leading symmetry-preserving rainbow-ladder approximation. In the chiral limit, the pion and its partner sigma degenerate at the critical temperature $T_c$. At $T\gtrsim T_c$, it is found that the pion rapidly dissociates, which signals deconfinement phase transition. Beyond the chiral limit, the pion dissociation temperature can be used to define the pseudo-critical temperature of chiral phase crossover, which is consistent with that obtained by the maximum point of the chiral susceptibility. The parallel analysis for kaon and pseudoscalar $s\bar{s}$ suggests that heavy mesons may survive above $T_c$.

   hep-phnucl-thCPC(2023)·9 citations
5. 05*

   Charged and Neutral ${\bar{B}}_{u,d,s}\to \gamma$ Form Factors from Light Cone Sum Rules at NLO

   Tadeusz Janowski🇬🇧 · Ben Pullin🇬🇧 · Roman Zwicky🇬🇧

   We present the first analytic $\mathcal{O}({\alpha }_s)$-computation at twist-$1$,$2$ of the ${\bar{B}}_{u,d,s}\to \gamma$ form factors within the framework of sum rules on the light-cone. These form factors describe the charged decay ${\bar{B}}_u\to \gamma {\ell }^{-}\bar{\nu }$, contribute to the flavour changing neutral currents ${\bar{B}}_{d,s}\to \gamma {\ell }^{+}{\ell }^{-}$ and serve as inputs to more complicated processes. We provide a fit in terms of a $z$-expansion with correlation matrix and extrapolate the form factors to the kinematic endpoint by using the $g_{B{B}^{\ast }\gamma }$ couplings as a constraint. Analytic results are available in terms of multiple polylogarithms as ancillary files. We give binned predictions for the ${\bar{B}}_u\to \gamma {\ell }^{-}\bar{\nu }$ branching ratio along with the associated correlation matrix. By comparing with three SCET-computations we extract the inverse moment $B$-meson distribution amplitude parameter ${\lambda }_B=360(110)\text{MeV}$. The uncertainty thereof could be improved by a more dedicated analysis. In passing, we extend the photon distribution amplitude to include quark mass corrections with a prescription for the magnetic vacuum susceptibility, ${\chi }_q$, compatible with the twist-expansion. The values ${\chi }_q=3.21(15){\text{GeV}}^{-2}$ and ${\chi }_s=3.79(17){\text{GeV}}^{-2}$ are obtained.

   hep-phhep-exJHEP(2021)·50 citations
6. 06*

   Radiative Decays of Heavy-light Mesons and the $f_{H,H^{\ast },H_1}^{(T)}$ Decay Constants

   Ben Pullin🇬🇧 · Roman Zwicky🇬🇧

   The on-shell matrix elements, or couplings $g_{H{H}^{\ast }(H_1)\gamma }$, describing the $B(D{)}_q^{\ast }\to B(D{)}_q\gamma$ and $B_{1q}\to B_q\gamma$ ($q=u,d,s$) radiative decays, are determined from light-cone sum rules at next-to-leading order for the first time. Two different interpolating operators are used for the vector meson, providing additional robustness to our results. For the $D^{\ast }$-meson, where some rates are experimentally known, agreement is found. The couplings are of additional interest as they govern the lowest pole residue in the $B(D)\to \gamma$ form factors which in turn are connected to QED-corrections in leptonic decays $B(D)\to \ell \bar{\nu }$. Since the couplings and residues are related by the decay constants $f_{H^{\ast }(H_1)}$ and $f_{H^{\ast }(H_1)}^T$ respectively, we determine them at next-leading order as a by-product. The quantities $\{f_{H^{\ast }}^T,f_{H_1},f_{H_1}^T\}$ have not previously been subjected to a QCD sum rule determination. All results are compared with the existing experimental and theoretical literature.

   hep-phhep-exJHEP(2021)·56 citations
7. 07*

   Reformulation of a likelihood approach to fake-lepton estimation in the framework of Bayesian inference

   Johannes Erdmann🇩🇪 · Cornelius Grunwald🇩🇪 · Kevin Kröninger🇩🇪 · Salvatore La Cagnina🇩🇪 · Lars Röhrig🇩🇪 · Erich Varnes🇺🇸

   Prompt isolated leptons are essential in many analyses in high-energy particle physics but are subject to fake-lepton background, i.e. objects that mimic the lepton signature. The fake-lepton background is difficult to estimate from simulation and is often directly determined from data. A popular method is the matrix method, which however suffers from several limitations. This paper recapitulates an alternative approach based on a likelihood with Poisson constraints and reformulates the problem from a different starting point in the framework of Bayesian statistics. The equality of both approaches is shown and several cases are studied in which the matrix method is limited. In addition, the fake lepton background is recalculated and compared to the estimate with the matrix method in an example top-quark measurement.

   hep-phhep-exphysics.data-anNucl.Instrum.Meth.A(2022)·6 citations
8. 08*

   New Discovery Modes for a Light Charged Higgs Boson at the LHC

   A. Arhrib🇲🇦 · R. Benbrik🇲🇦 · M. Krab🇲🇦 · B. Manaut🇲🇦 · S. Moretti🇬🇧 · Yan Wang🇨🇳 · Qi-Shu Yan🇨🇳

   At the Large Hadron Collider (LHC), both the ATLAS and CMS Collaborations have been searching for light charged Higgs bosons via top (anti)quark production and decays channels, like $pp\to t\bar{t}$ with one top (anti)quark decaying into a charged Higgs boson and a $b$ (anti)quark, when the decay is kinematically open (i.e., when $m_{H^{\pm }}\lesssim m_t$). In this paper, we propose new searches at the LHC involving light charged Higgs bosons via their pair production channels like $pp\to H^{\pm }h/A$ and $pp\to H^{+}{H}^{-}$ in the 2-Higgs Doublet Model (2HDM) Type-I and -X scenarios. By focusing on the case where the heavy $H$ state plays the role of the Standard Model (SM)-like Higgs boson with a mass near 125 GeV, we study the aforementioned Higgs boson pair production channels and investigate their bosonic decays, such as $H^{\pm }\to W^{\pm }h$ and/or $H^{\pm }\to W^{\pm }A$. We demonstrate that for a light charged Higgs boson state, with $m_{H^{\pm }}\lesssim m_t$, at the LHC, such di-Higgs production and decay channels can give rise to signatures with event rates much larger than those emerging from $pp\to t\bar{t}\to t\bar{b}{H}^{-}$ + c.c.. We specifically study $h/A\to b\bar{b}$ and ${\tau }^{+}{\tau }^{-}$ decays. We, therefore, claim that the discussed combination of new production and decay modes can result in an alternative discovery channel for charged Higgs bosons lighter than the top (anti)quark at the LHC within the above two 2HDM Types. Finally, in order to motivate experimentalists in ATLAS and CMS to search for such signatures, we propose 16 Benchmark Points (BPs) which are compatible with both theoretical and experimental constraints.

   hep-phJHEP(2021)·37 citations
9. 09*

   Towards EPPS21 nuclear PDFs

   Kari J. Eskola🇫🇮 · Petja Paakkinen🇪🇸 · Hannu Paukkunen🇫🇮 · Carlos A. Salgado🇪🇸

   We report on the progress in updating our global analysis of nuclear PDFs. In particular, we will discuss the inclusion of double differential 5.02 TeV dijet and D-meson measurements, as well as 8.16 TeV W-production data from p-Pb collisions at the LHC. The new EPPS21 analysis will also involve recent JLab data for deep-inelastic scattering. As a novel aspect within our approach, we now also quantify the impact of free-proton PDF uncertainties on our extraction of nuclear PDFs.

   hep-phSciPost Phys.Proc.(2022)·11 citations
10. 10*

    The electron mass shift in an intense plane wave

    A. Di Piazza🇩🇪 · T. Pătuleanu🇩🇪

    Upcoming experiments on the interaction of electrons with intense laser fields are envisaged to become more and more accurate, which calls for theoretical computations of rates and probabilities with correspondingly higher precision. In strong-field QED this requires the knowledge of radiative corrections to be added to leading-order results. Here, we first derive the mass operator in momentum space of an off-shell electron in the presence of an arbitrary plane wave. By taking the average of the mass operator in momentum space over an on-shell electron state, we obtain a new representation, equivalent to but more compact than the known one computed in [Sov. Phys. JETP \textbf{42}, 400 (1975)]. Moreover, we use the obtained mass operator to determine the electron mass shift in an arbitrary plane wave, which generalizes the already known expression in a constant crossed field. The spin-dependent part of the electron mass shift can be related to the anomalous magnetic moment of the electron in the plane wave. We show that within the locally constant field approximation it is possible to conveniently define a local expression of the electron anomalous magnetic moment, which reduces to the known expression in a constant crossed field. Beyond the locally constant field approximation, however, the interaction between the electron and the plane wave is non-local such that it is not possible to conveniently introduce an electron anomalous magnetic moment.

    hep-phPRD(2021)·14 citations
11. 11*

    Correcting event-by-event fluctuations in heavy-ion collisions for exact global conservation laws with the generalized subensemble acceptance method

    Volodymyr Vovchenko🇺🇸

    We introduce the subensemble acceptance method 2.0 (SAM-2.0) -- a procedure to correct cumulants of a random number distribution inside a subsystem for the effect of exact global conservation of a conserved quantity to which this number is correlated, with applications to measurements of event-by-event fluctuations in heavy-ion collisions. The method expresses the corrected cumulants in terms of the cumulants inside and outside the subsystem that are not subject to the exact conservation. The derivation assumes that all probability distributions associated with the cumulants are peaked at the mean values but are otherwise of arbitrary shape. The formalism reduces to the original SAM [V. Vovchenko et al., Phys.Lett.B 811 (2020) 135868 [arXiv:2003.13905]] when applied to a coordinate space subvolume of a uniform thermal system. As the new method is restricted neither to the uniform systems nor to the coordinate space, it is applicable to fluctuations measured in heavy-ion collisions at various collision energies in different momentum space acceptances. The SAM-2.0 thus brings the experimental measurements and theoretical calculations of event-by-event fluctuations closer together, as the latter are typically performed without the account of exact global conservation.

    hep-phnucl-thPRC(2022)·32 citations
12. 12*

    A methodology for theory uncertainties in the SMEFT

    Michael Trott🇩🇰

    A process specific methodology is defined to systematically assign theoretical uncertainties in the Standard Model Effective Field Theory when performing leading order global fits. The method outlined also minimises the computational and theoretical burden to systematically advance such analyses to dimension eight.

    hep-phhep-exPRD(2021)·34 citations
13. 13*

    The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter

    Susan Gardner🇺🇸 · Samuel D. McDermott🇺🇸 · Brian Yanny🇺🇸

    The growing trove of precision astrometric observations from the Gaia space telescope and other surveys is revealing the structure and dynamics of the Milky Way in ever more exquisite detail. We summarize the current status of our understanding of the structure and the characteristics of the Milky Way, and we review the emerging picture: the Milky Way is evolving through interactions with the massive satellite galaxies that stud its volume, with evidence pointing to a cataclysmic past. It is also woven with stellar streams, and observations of streams, satellites, and field stars offer new constraints on its dark matter, both on its spatial distribution and its fundamental nature. The recent years have brought much focus to the study of dwarf galaxies found within our Galaxy's halo and their internal matter distributions. In this review, we focus on the predictions of the cold dark matter paradigm at small mass scales through precision astrometric measurements, and we summarize the modern consensus on the extent to which small-scale probes are consistent with this paradigm. We note the discovery prospects of these studies, and also how they intertwine with probes of the dynamics and evolution of the Milky Way in various and distinct ways.

    ↳ astro-ph.GAastro-ph.COastro-ph.HEhep-phPPNP(2021)·20 citations
14. 14*

    A False Vacuum Skyrme Model for Nuclear Matter

    L. A. Ferreira🇧🇷 · L. R. Livramento🇧🇷

    The low energy regime of Quantum Chromodynamics (QCD) presents enormous challenges due to its large coupling. Effective field theories, like the Skyrme model, are useful approaches to study properties of strong interaction at hadronic scales. We propose a Skyrme-type model with a self-dual sector and that treats the density of the baryonic charge as a self-interacting fluid. The dynamics reduces to Coleman's false vacuum problem for a scalar field that is a fractional power of that density. The main result is that such a Skyrme-type model is the first one to reproduce, with good accuracy, the experimental values of radii and binding energies for a very wide range of the mass number. The robust and simple properties of the model lead to many possible generalizations with implications not only in nuclear physics but also in other areas of Physics.

    ↳ hep-thhep-lathep-phnucl-thJ.Phys.G(2022)·14 citations
15. 15*

    Tidal Deformation and Radial Pulsations of Neutron Star with Holographic Multiquark Core

    Sitthichai Pinkanjanarod🇹🇭 · Piyabut Burikham🇹🇭 · Supakchai Ponglertsakul🇹🇭

    Tidal deformation of neutron star with multiquark core is calculated using nuclear and multiquark equations of state. The equation of state of the multiquark phase from the holographic Sakai-Sugimoto~(SS) model is relatively stiff in the low density region and becomes softer at high densities. The values of Love number and dimensionless deformation parameter, $k_2$ and $\Lambda$, are found to be within the physically viable range under the present constraints. Radial pulsation frequencies of the multiquark core for $n=0-5$ modes are calculated for the entire mass range. For $M_{\mathrm{core}}\simeq 2M_{\odot }$, the fundamental-mode frequency is approximately $2.5$ kHz for the energy density scale ${ϵ}_s=23.2037$ GeV/fm${}^3$ of the holographic SS model, this frequency is proportional to $\sqrt{{ϵ}_s}$.

    ↳ gr-qchep-phEPJC(2022)·8 citations
16. 16*

    Gravitational Collider Physics via Pulsar-Black Hole Binaries II: Fine and Hyperfine Structures are Favored

    Xi Tong🇨🇳 · Yi Wang🇨🇳 · Hui-Yu Zhu🇨🇳

    A rotating black hole can be clouded by light bosons via superradiance, and thus acquire an atom-like structure. If such a gravitational atom system is companioned with a pulsar, the pulsar can trigger transitions between energy levels of the gravitational atom, and these transitions can be detected by pulsar timing. We show that in such pulsar-black hole systems, fine and hyperfine structure transitions are more likely to be probed than the Bohr transition. Also, the calculation of these fine and hyperfine structure transitions are under better analytic control. Thus, these fine and hyperfine structure transitions are more ideal probes in the search for gravitational collider signals in pulsar-black hole systems.

    ↳ astro-ph.HEgr-qchep-phhep-thApJ(2022)·29 citations
17. 17*

    The Minimum Testable Abundance of Primordial Black Holes at Future Gravitational-Wave Detectors

    V. De Luca🇨🇭 · G. Franciolini🇨🇭 · P. Pani🇮🇹 · A. Riotto🇨🇭

    The next generation of gravitational-wave experiments, such as Einstein Telescope, Cosmic Explorer and LISA, will test the primordial black hole scenario. We provide a forecast for the minimum testable value of the abundance of primordial black holes as a function of their masses for both the unclustered and clustered spatial distributions at formation. In particular, we show that these instruments may test abundances, relative to the dark matter, as low as $10^{-10}$.

    ↳ astro-ph.COgr-qchep-phJCAP(2021)·76 citations
18. 18*

    Matter matters in Einstein-Cartan gravity

    Georgios K. Karananas🇩🇪 · Mikhail Shaposhnikov🇨🇭 · Andrey Shkerin🇺🇸 · Sebastian Zell🇨🇭

    We study scalar, fermionic and gauge fields coupled nonminimally to gravity in the Einstein-Cartan formulation. We construct a wide class of models with nondynamical torsion whose gravitational spectra comprise only the massless graviton. Eliminating non-propagating degrees of freedom, we derive an equivalent theory in the metric formulation of gravity. It features contact interactions of a certain form between and among the matter and gauge currents. We also discuss briefly the inclusion of curvature-squared terms.

    ↳ hep-thgr-qchep-phPRD(2021)·50 citations
19. 19*

    Neutrino: chronicles of an aloof protagonist

    Alejandra Melfo🇻🇪 · Goran Senjanovic🇩🇪

    We give a brief account of the history of neutrino, and how that most aloof of all particles has shaped our search for a theory of fundamental interactions ever since it was theoretically proposed. We introduce the necessary concepts and phenomena in a non-technical language aimed at a physicist with some basic knowledge of quantum mechanics. In showing that neutrino mass could be the door to new physics beyond the Standard Model, we emphasize the need to frame the issue in the context of a complete theory, with testable predictions accessible to present and near future experiments. We argue in favor of the Minimal Left-Right Symmetric theory as the strongest candidate for such theory, connecting neutrino mass with parity breakdown in nature. This is the theory that led originally to neutrino mass and the seesaw mechanism behind its smallness, but even more important, the theory that sheds light on a fundamental question that touches us all: the symmetry between left and right.

    ↳ physics.hist-phhep-exhep-phhep-thMod.Phys.Lett.A(2022)·6 citations
20. 20*

    Updated physics performance of the ESSnuSB experiment

    A. Alekou🇨🇭 · E. Baussan🇫🇷 · N. Blaskovic Kraljevic🇸🇪 · M. Blennow🇸🇪 · M. Bogomilov🇧🇬 · E. Bouquerel🇫🇷 · A. Burgman🇸🇪 · C. J. Carlile🇸🇪 · J. Cederkall🇸🇪 · P. Christiansen🇸🇪 · M. Collins🇸🇪 · E. Cristaldo Morales🇮🇹 and 39 other authors

    In this paper, we present the physics performance of the ESSnuSB experiment in the standard three flavor scenario using the updated neutrino flux calculated specifically for the ESSnuSB configuration and updated migration matrices for the far detector. Taking conservative systematic uncertainties corresponding to a normalization error of $5\%$ for signal and $10\%$ for background, we find that there is $10\sigma$ $(13\sigma )$ CP violation discovery sensitivity for the baseline option of 540 km (360 km) at ${\delta }_{\mathrm{CP}}=\pm 90^{\circ }$. The corresponding fraction of ${\delta }_{\mathrm{CP}}$ for which CP violation can be discovered at more than $5\sigma$ is $70\%$. Regarding CP precision measurements, the $1\sigma$ error associated with ${\delta }_{\mathrm{CP}}=0^{\circ }$ is around $5^{\circ }$ and with ${\delta }_{\mathrm{CP}}=-90^{\circ }$ is around $14^{\circ }$ $(7^{\circ })$ for the baseline option of 540 km (360 km). For hierarchy sensitivity, one can have $3\sigma$ sensitivity for 540 km baseline except ${\delta }_{\mathrm{CP}}=\pm 90^{\circ }$ and $5\sigma$ sensitivity for 360 km baseline for all values of ${\delta }_{\mathrm{CP}}$. The octant of ${\theta }_{23}$ can be determined at $3\sigma$ for the values of: ${\theta }_{23}>51^{\circ }$ (${\theta }_{23}<42^{\circ }$ and ${\theta }_{23}>49^{\circ }$) for baseline of 540 km (360 km). Regarding measurement precision of the atmospheric mixing parameters, the allowed values at $3\sigma$ are: $40^{\circ }<{\theta }_{23}<52^{\circ }$ ($42^{\circ }<{\theta }_{23}<51.5^{\circ }$) and $2.485\times 10^{-3}$ eV${}^2<\Delta m_{31}^2<2.545\times 10^{-3}$ eV${}^2$ ($2.49\times 10^{-3}$ eV${}^2<\Delta m_{31}^2<2.54\times 10^{-3}$ eV${}^2$) for the baseline of 540 km (360 km).

    ↳ hep-exhep-phphysics.ins-detEPJC(2021)·51 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.