Mon·Mar 1, 2021Monday·March 1, 2021

1. 01*

   QCD phase diagram in a constant magnetic background. Inverse magnetic catalysis: where models meet the lattice

   Jens O. Andersen🇳🇴

   Magnetic catalysis is the enhancement of a condensate due to the presence of an external magnetic field. Magnetic catalysis at $T=0$ is a robust phenomenon in low-energy theories and models of QCD as well as in lattice simulations. We review the underlying physics of magnetic catalysis from both perspectives. The quark-meson model is used as a specific example of a model that exhibits magnetic catalysis. Regularization and renormalization are discussed and we pay particular attention to a consistent and correct determination of the parameters of the Lagrangian using the on-shell renormalization scheme. A straightforward application of the quark-meson model and the NJL model leads to the prediction that the chiral transition temperature $T_{\chi }$ is increasing as a function of the magnetic field $B$. This is in disagreement with lattice results, which show that $T_{\chi }$ is a decreasing function of $B$, independent of the pion mass. The behavior can be understood in terms of the so-called valence and sea contributions to the quark condensate and the competition between them. We critically examine these ideas as well recent attempts to improve low-energy models using lattice input.

   hep-phEPJA(2021)·48 citations
2. 02*

   $t\bar{t}{W}^{\pm }$ at NLO accuracy with realistic final states

   Giuseppe Bevilacqua🇭🇺

   In this proceedings we summarize state-of-the-art theoretical predictions for the process of $t\bar{t}{W}^{\pm }$ production at the LHC. After a review of the status of inclusive calculations, we discuss recent advancements in exclusive predictions.

   hep-ph0 citations
3. 03*

   Test of the nonrelativistic $c\bar{c}$ potential

   Ulugbek Yakhshiev🇰🇷

   We analyze the charmonium states by testing a phenomenological nonrelativistic potential and propose a new set of parameters. This new set of parameters are fixed using only the lowest lying S-wave states of charmonia where the spin-orbit and tensor interactions will not contribute. After fitting the parameters we analyze the whole fine structure of charmonium states taking into account the spin-orbit and tensor interactions too. Calculations showed that the nonrelativistic potential model with the phenomenologically defined parameters is indeed well approximation for describing the charmonium states.

   hep-phnucl-thJ.Korean Phys.Soc.(2021)·3 citations
4. 04*

   New Physics Searches at the BESIII Experiment

   Shenjian Chen🇨🇳 · Stephen Lars Olsen🇨🇳

   The Standard Model (SM) of particle physics, comprised of the unified electro-weak (EW) and Quantum Chromodynamic (QCD) theories, accurately explains almost all experimental results related to the micro-world, and has made a number of predictions for previously unseen particles, most notably the Higgs scalar boson, that were subsequently discovered. As a result, the SM is currently universally accepted as the theory of the fundamental particles and their interactions. However, in spite of its numerous successes, the SM has a number of apparent shortcomings including: many free parameters that must be supplied by experimental measurements; no mechanism to produce the dominance of matter over antimatter in the universe; and no explanations for gravity, the dark matter in the universe, neutrino masses, the number of particle generations, etc. Because of these shortcomings, there is considerable incentive to search for evidence for new, non-SM physics phenomena that might provide important clues about what a new, beyond the SM theory (BSM) might look like. Although the center-of-mass energies that BESIII can access are far below the energy frontier, searches for new, BSM physics are an important component of its research program. Here we describe ways that BESIII looks for signs of BSM physics by measuring rates for processes that the SM predicts to be forbidden or very rare, searching for non-SM particles such as dark photons, making precision tests of SM predictions, and looking for violations of the discrete symmetries $C$ and $CP$ in processes for which the SM-expectations are immeasurably small.

   hep-phhep-exnucl-exNatl.Sci.Rev.(2021)·10 citations
5. 05*

   Searching for New Physics with multilepton events at PADME

   Gabriele Martelli🇮🇹 · Paolo Ciafaloni🇮🇹 · Mauro Raggi🇮🇹

   The PADME experiment is searching for the Dark Photon $A^{\prime }$ in the $e^{+}{e}^{-}\to \gamma A^{\prime }$ process, assuming a $A^{\prime }$ decay into invisible particles. In extended Dark Sector models, a Dark Higgs $h^{\prime }$ can be produced alongside $A^{\prime }$ in the process $e^{+}{e}^{-}\to h^{\prime }{A}^{\prime }$. If the $h^{\prime }$ mass is greater than twice the $A^{\prime }$ mass the final state will be composed by three $e^{+}{e}^{-}$ pairs. Such extremely rare process is explorable by the PADME experiment, which could get a first measure and impose limits on models of physics beyond the Standard Model.

   hep-phhep-exNuovo Cim.C(2021)·1 citation
6. 06*

   On the effective lifetime of $B_s\to \mu \mu \gamma$

   Alexandre Carvunis🇫🇷 · Francesco Dettori🇮🇹 · Shireen Gangal🇫🇷 · Diego Guadagnoli🇫🇷 · Camille Normand🇫🇷

   We consider the $B_s^0\to {\mu }^{+}{\mu }^{-}\gamma$ effective lifetime, and the related CP-phase sensitive quantity $A_{\Delta {\Gamma }_s}^{\mu \mu \gamma }$, as a way to obtain qualitatively new insights on the current $B$-decay discrepancies. Through a fit comparing pre- to post-Moriond-2021 data we identify a few theory benchmark scenarios addressing these discrepancies, and featuring large CP violation in addition. We then explore the possibility of telling apart these scenarios with $A_{\Delta {\Gamma }_s}^{\mu \mu \gamma }$, once resonance-modeling and form-factor uncertainties are taken into account. We do so in both regions of low and high invariant di-lepton mass-squared $q^2$. For low $q^2$, we show how to shape the integration range in order to reduce the impact of the $\varphi$-resonance modelling on the $A_{\Delta {\Gamma }_s}^{\mu \mu \gamma }$ prediction. For high $q^2$, we find that the corresponding pollution from broad-charmonium resonances has a surprisingly small effect on $A_{\Delta {\Gamma }_s}^{\mu \mu \gamma }$. This is due to a number of cancellations, that can be traced back to the complete dominance of semi-leptonic operator contributions for high $q^2$ -- at variance with low $q^2$ -- and to $A_{\Delta {\Gamma }_s}^{\mu \mu \gamma }$ behaving like a ratio-of-amplitudes observable. Our study suggests that $A_{\Delta {\Gamma }_s}^{\mu \mu \gamma }$ is -- especially at high $q^2$ -- a potentially valuable probe of short-distance CP-violating effects in the very same Wilson coefficients that are associated to current $b\to s$ discrepancies. Its discriminating power, however, relies on progress in form-factor uncertainties. Interestingly, high $q^2$ is the region where $B_s^0\to {\mu }^{+}{\mu }^{-}\gamma$ is already being accessed experimentally, and the region where form factors are more accessible through non-perturbative QCD methods.

   hep-phhep-exJHEP(2021)·74 citations
7. 07*

   On the impact of the LHC Run2 data on general Composite Higgs scenarios

   Charanjit K. Khosa🇮🇹 · Veronica Sanz🇬🇧

   We study the the impact of Run2 LHC data on general Composite Higgs scenarios, where non-linear effects, mixing with additional scalars and new fermionic degrees of freedom could simultaneously contribute to the modification of Higgs properties. We obtain new experimental limits on the scale of compositeness, the mixing with singlets and doublets with the Higgs, and the mass and mixing angle of top-partners. We also show that for scenarios where new fermionic degrees of freedom are involved in electroweak symmetry breaking, there is an interesting interplay among Higgs coupling measurements, boosted Higgs properties, SMEFT global analyses, and direct searches for single- and double-production of vector-like quarks.

   hep-phAdv.High Energy Phys.(2022)·10 citations
8. 08*

   Two-loop leading colour QCD helicity amplitudes for top quark pair production in the gluon fusion channel

   Simon Badger🇮🇹 · Ekta Chaubey🇮🇹 · Heribertus Bayu Hartanto🇬🇧 · Robin Marzucca🇬🇧

   We present a complete set of analytic helicity amplitudes for top quark pair production via gluon fusion at two-loops in QCD. For the first time, we include corrections due to massive fermion loops which give rise to integrals over elliptic curves. We present the results of the missing master integrals needed to compute the amplitude and obtain an analytic form for the finite remainders in terms of iterated integrals using rationalised kinematics and finite field sampling. We also study the numerical evaluation of the iterated integrals.

   hep-phhep-thJHEP(2021)·43 citations
9. 09*

   NNLO QCD study of polarised $W^{+}{W}^{-}$ production at the LHC

   Rene Poncelet🇬🇧 · Andrei Popescu🇬🇧

   Longitudinal polarisation of the weak bosons is a direct consequence of Electroweak symmetry breaking mechanism providing an insight into its nature, and is instrumental in searches for physics beyond the Standard Model. We perform a polarisation study of the diboson production in the $pp\to e^{+}{\nu }_e{\mu }^{-}{\bar{\nu }}_{\mu }$ process at NNLO QCD in the fiducial setup inspired by experimental measurements at ATLAS. This is the first polarisation study at NNLO. We employ the double-pole approximation framework for the polarised calculation, and investigate NNLO effects arising in differential distributions.

   hep-phJHEP(2021)·57 citations
10. 10*

    $t\bar{t}W$ Production: a very complex process

    Marcos Miralles López (for the ATLAS Collaboration)🇪🇸

    These Monte Carlo studies describe the impact of higher order effects in both QCD and EW $t\bar{t}W$ production. Both next-to-leading inclusive and multileg setups are studied for $t\bar{t}W$ QCD production.

    hep-phhep-ex0 citations
11. 11*

    Leading-Color Two-Loop QCD Corrections for Three-Jet Production at Hadron Colliders

    S. Abreu🇨🇭 · F. Febres Cordero🇺🇸 · H. Ita🇩🇪 · B. Page🇫🇷 · V. Sotnikov🇩🇪

    We present the complete set of leading-color two-loop contributions required to obtain next-to-next-to-leading-order (NNLO) QCD corrections to three-jet production at hadron colliders. We obtain analytic expressions for a generating set of finite remainders, valid in the physical region for three-jet production. The analytic continuation of the known Euclidean-region results is determined from a small set of numerical evaluations of the amplitudes. We obtain analytic expressions that are suitable for phenomenological applications and we present a C++ library for their efficient and stable numerical evaluation.

    hep-phJHEP(2021)·94 citations
12. 12*

    Baryogenesis via gauge field production from a relaxing Higgs

    Yann Cado🇪🇸 · Benedict von Harling🇪🇸 · Eduard Masso🇪🇸 · Mariano Quiros🇪🇸

    We show that the baryon asymmetry of the universe can be explained in models where the Higgs couples to the Chern-Simons term of the hypercharge group and is away from the late-time minimum of its potential during inflation. The Higgs then relaxes toward this minimum once inflation ends which leads to the production of (hyper)magnetic helicity. We discuss the conditions under which this helicity can be approximately conserved during its joint evolution with the thermal plasma. At the electroweak phase transition the helicity is then converted into a baryon asymmetry by virtue of the chiral anomaly in the standard model. We propose a simple model which realizes this mechanism and show that the observed baryon asymmetry of the universe can be reproduced.

    hep-phJCAP(2021)·11 citations
13. 13*

    Higher-spin particles at high-energy colliders

    Juan Carlos Criado🇬🇧 · Abdelhak Djouadi🇪🇸 · Niko Koivunen🇪🇪 · Martti Raidal🇪🇪 · Hardi Veermäe🇪🇪

    Using an effective field theory approach for higher-spin fields, we derive the interactions of colour singlet and electrically neutral particles with a spin higher than unity, concentrating on the spin-3/2, spin-2, spin-5/2 and spin-3 cases. We compute the decay rates and production cross sections in the main channels for spin-3/2 and spin-2 states at both electron-positron and hadron colliders, and identify the most promising novel experimental signatures for discovering such particles at the LHC. The discussion is qualitatively extended to the spin-5/2 and spin-3 cases. Higher-spin particles exhibit a rich phenomenology and have signatures that often resemble the ones of supersymmetric and extra-dimensional theories. To enable further studies of higher-spin particles at collider and beyond, we collect the relevant Feynman rules and other technical details.

    hep-phhep-exhep-thnucl-thJHEP(2021)·13 citations
14. 14*

    LEvEL: Low-Energy Neutrino Experiment at the LHC

    Kevin J. Kelly🇺🇸 · Pedro A. N. Machado🇺🇸 · Alberto Marchionni🇺🇸 · Yuber F. Perez-Gonzalez🇺🇸

    We propose the operation of \textbf{LEvEL}, the Low-Energy Neutrino Experiment at the LHC, a neutrino detector near the Large Hadron Collider Beam Dump. Such a detector is capable of exploring an intense, low-energy neutrino flux and can measure neutrino cross sections that have previously never been observed. These cross sections can inform other future neutrino experiments, such as those aiming to observe neutrinos from supernovae, allowing such measurements to accomplish their fundamental physics goals. We perform detailed simulations to determine neutrino production at the LHC beam dump, as well as neutron and muon backgrounds. Measurements at a few to ten percent precision of neutrino-argon charged current and neutrino-nucleus coherent scattering cross sections are attainable with 100~ton-year and 1~ton-year exposures at LEvEL, respectively, concurrent with the operation of the High Luminosity LHC. We also estimate signal and backgrounds for an experiment exploiting the forward direction of the LHC beam dump, which could measure neutrinos above 100 GeV.

    hep-phhep-exJHEP(2021)·11 citations
15. 15*

    Bayesian analysis of multimessenger M-R data with interpolated hybrid EoS

    A. Ayriyan🇷🇺 · D. Blaschke🇵🇱 · A. G. Grunfeld🇦🇷 · D. Alvarez-Castillo🇵🇱 · H. Grigorian🇷🇺 · V. Abgaryan🇷🇺

    We introduce a family of equations of state (EoS) for hybrid neutron star (NS) matter that is obtained by a two-zone parabolic interpolation between a soft hadronic EoS at low densities and a set of stiff quark matter EoS at high densities within a finite region of chemical potentials ${\mu }_H<\mu <{\mu }_Q$. Fixing the hadronic EoS as the APR one and choosing the color-superconducting, nonlocal NJL model with two free parameters for the quark phase, we perform Bayesian analyses with this two-parameter family of hybrid EoS. Using three different sets of observational constraints that include the mass of PSR J0740+6620, the tidal deformability for GW170817, and the mass-radius relation for PSR J0030+0451 from NICER as obligatory (set 1), while set 2 uses the possible upper limit on the maximum mass from GW170817 as an additional constraint and set 3 instead of the possibility that the lighter object in the asymmetric binary merger GW190814 is a neutron star. We confirm that in any case, the quark matter phase has to be color superconducting with the dimensionless diquark coupling approximately fulfilling the Fierz relation ${\eta }_D=0.75$ and the most probable solutions exhibiting a proportionality between ${\eta }_D$ and ${\eta }_V$, the coupling of the repulsive vector interaction that is required for a sufficiently large maximum mass. We used the Bayesian analysis to investigate with the method of fictitious measurements the consequences of anticipating different radii for the massive $2M_{\odot }$ PSR J0740+6220 for the most likely equation of state. With the actual outcome of the NICER radius measurement on PSR J0740+6220 we could conclude that for the most likely hybrid star EoS would not support a maximum mass as large as $2.5M_{\odot }$ so that the event GW190814 was a binary black hole merger.

    ↳ astro-ph.HEhep-phnucl-thEPJA(2021)·64 citations
16. 16*

    Reconstruction of the neutrino mass as a function of redshift

    Christiane S. Lorenz🇨🇭 · Lena Funcke🇨🇦 · Matthias Löffler🇨🇭 · Erminia Calabrese🇬🇧

    We reconstruct the neutrino mass as a function of redshift, z, from current cosmological data using both standard binned priors and linear spline priors with variable knots. Using cosmic microwave background temperature, polarization and lensing data, in combination with distance measurements from baryonic acoustic oscillations and supernovae, we find that the neutrino mass is consistent with $\sum m_{\nu }(z)$ = const. We obtain a larger bound on the neutrino mass at low redshifts coinciding with the onset of dark energy domination, $\sum m_{\nu }(z=0)$ < 1.46 eV (95% CL). This result can be explained either by the well-known degeneracy between $\sum m_{\nu }$ and ${\Omega }_{\Lambda }$ at low redshifts, or by models in which neutrino masses are generated very late in the Universe. We finally convert our results into cosmological limits for models with non-relativistic neutrino decay and find $\sum m_{\nu }$ < 0.21 eV (95% CL), which would be out of reach for the KATRIN experiment.

    ↳ astro-ph.COhep-phPRD(2021)·52 citations
17. 17*

    Functional renormalization group and 2PI effective action formalism

    Jean-Paul Blaizot🇫🇷 · Jan M. Pawlowski🇩🇪 · Urko Reinosa🇫🇷

    We combine two non-perturbative approaches, one based on the two-particle-irreducible (2PI) action, the other on the functional renormalization group (fRG), in an effort to develop new non-perturbative approximations for the field theoretical description of strongly coupled systems. In particular, we exploit the exact 2PI relations between the two-point and four-point functions in order to truncate the infinite hierarchy of equations of the functional renormalization group. The truncation is "exact" in two ways. First, the solution of the resulting flow equation is independent of the choice of the regulator. Second, this solution coincides with that of the 2PI equations for the two-point and the four-point functions, for any selection of two-skeleton diagrams characterizing a so-called $\Phi$-derivable approximation. The transformation of the equations of the 2PI formalism into flow equations offers new ways to solve these equations in practice, and provides new insight on certain aspects of their renormalization. It also opens the possibility to develop approximation schemes going beyond the strict $\Phi$-derivable ones, as well as new truncation schemes for the fRG hierarchy.

    ↳ hep-thcond-mat.othercond-mat.str-elhep-phAnnals Phys.(2021)·36 citations
18. 18*

    Chain Early Dark Energy: Solving the Hubble Tension and Explaining Today's Dark Energy

    Katherine Freese🇺🇸 · Martin Wolfgang Winkler🇸🇪

    We propose a new model of Early Dark Energy (EDE) as a solution to the Hubble tension in cosmology, the apparent discrepancy between local measurements of the Hubble constant $H_0\simeq 74$ km s${}^{-1}$ Mpc${}^{-1}$ and $H_0\simeq 67$ km s${}^{-1}$ Mpc${}^{-1}$ inferred from the Cosmic Microwave Background (CMB). In Chain EDE, the Universe undergoes a series of first order phase transitions, starting at a high energy vacuum in a potential, and tunneling down through a chain of every lower energy metastable minima. As in all EDE models, the contribution of the vacuum energy to the total energy density of the universe is initially negligible, but reaches $\sim 10\%$ around matter-radiation equality, before cosmological data require it to redshift away quickly -- at least as fast as radiation. We indeed obtain this required behavior with a series of $N$ tunneling events, and show that for $N>600$ the phase transitions are rapid enough to allow fast percolation and thereby avoid large scale anisotropies in the CMB. We construct a specific example of Chain EDE featuring a scalar field in a quasiperiodic potential (a tilted cosine), which is ubiquitous in axion physics and, therefore, carries strong theoretical motivation. Interestingly, the energy difference between vacua can be roughly the size of today's Dark Energy (meV scale). Therefore, the end result of Chain EDE could provide a natural explanation of Dark Energy, if the tunneling becomes extremely slow in the final step before the field reaches zero (or negative) energy. We discuss a simple mechanism which can stop the scalar field in the desired minimum. Thus Chain EDE offers the exciting prospect to explain EDE and Dark Energy by the same scalar field.

    ↳ astro-ph.COhep-phhep-thPRD(2021)·66 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.