Wed·Mar 17, 2021Wednesday·March 17, 2021

1. 01*

   Triggering on Emerging Jets

   Dylan Linthorne🇨🇦 · Daniel Stolarski🇨🇦

   Confining dark sectors at the GeV scale can lead to novel collider signatures including those termed emerging jets with large numbers of displaced vertices. The triggers at the LHC experiments were not designed with this type of new physics in mind, and triggering can be challenging, especially if the mediator is relatively light and/or has quantum numbers such that additional jets are not automatically produced in each event. We show that the efficiency and the total event rate at current triggers can be significantly improved by considering initial state radiation of the events, with the largest increase in rate coming from simulation of two additional jets. We also explore possible new triggers that employ hit counts in different tracker layers as input into a machine learning algorithm. We show that these new triggers can have reasonably low background rates, and that they are sensitive to a wide range of new physics parameters even when trained on a single model.

   hep-phhep-exPRD(2021)·25 citations
2. 02*

   Sterile Neutrino Dark Matter from Generalized $CPT$-Symmetric Early-Universe Cosmologies

   Adam Duran🇺🇸 · Logan Morrison🇺🇸 · Stefano Profumo🇺🇸

   We generalize gravitational particle production in a radiation-dominated $CPT$-symmetric universe to non-standard, but also $CPT$-symmetric early universe cosmologies. We calculate the mass of a right-handed "sterile" neutrino needed for it to be the cosmological dark matter. Since generically sterile neutrinos mix with the Standard Model active neutrinos, we use state-of-the-art tools to compute the expected spectrum of gamma rays and high-energy active neutrinos from ultra-heavy sterile neutrino dark matter decay. We demonstrate that the sterile neutrinos are never in thermal equilibrium in the early universe. We show that very high-energy Cherenkov telescopes might detect a signal for sterile neutrino lifetimes up to around 10${}^{27}$ s, while a signal in high-energy neutrino telescopes such as IceCube could be detectable for lifetimes up to 10${}^{30}$ s, offering a better chance of detection across a vast landscape of possible masses.

   hep-phastro-ph.COastro-ph.HEgr-qcPRD(2021)·2 citations
3. 03*

   Anti-$k_T$ jet function at next-to-next-to-leading order

   Hao-yu Liu🇨🇳 · Xiaohui Liu🇨🇳 · Sven-Olaf Moch🇩🇪

   Jets constructed via clustering algorithms (e.g., anti-$k_T$, soft-drop) have been proposed for many precision measurements, such as the strong coupling ${\alpha }_s$ and the nucleon intrinsic dynamics. However, the theoretical accuracy is affected by missing QCD corrections at higher orders for the jet functions in the associated factorization theorems. Their calculation is complicated by the jet clustering procedure. In this work, we propose a method to evaluate jet functions at higher orders in QCD. The calculation involves the phase space sector decomposition with suitable soft subtractions. As a concrete example, we present the quark-jet function using the anti-$k_T$ algorithm with E-scheme recombination at next-to-next-to-leading order.

   hep-phnucl-thPRD(2021)·15 citations
4. 04*

   Particular textures of the minimal seesaw model

   Zhen-Hua Zhao🇨🇳 · Yan-Bin Sun🇨🇳 · Shan-Shan Jiang🇨🇳

   Following the Occam's razor principle, we explore the particular textures (featuring texture zeros and equalities) of the Dirac neutrino mass matrix in the minimal seesaw model (where only two right-handed neutrinos $N_1^{}$ and $N_2^{}$ are responsible for the generation of the light neutrino masses), in light of current neutrino experimental results and leptogenesis. The study will be performed for two particular patterns of the Majorana mass matrix $M_{\mathrm{R}}^{}$ for $N_1^{}$ and $N_2^{}$: (A) $M_{\mathrm{R}}^{}$ being diagonal $\left(\begin{array}{cc}{M}_1^{}& 0\\ 0& M_2^{}\end{array}\right)$; (B) $M_{\mathrm{R}}^{}$ being of the form $\left(\begin{array}{cc}0& M\\ M& 0\end{array}\right)$.

   hep-phNPB(2021)·5 citations
5. 05*

   Majorana Fermion Dark Matter in Minimally Extended Left-Right Symmetric Model

   M. J. Neves🇧🇷 · Nobuchika Okada🇺🇸 · Satomi Okada🇺🇸

   We present a minimal extension of the left-right symmetric model based on the gauge group $SU(3{)}_c\times SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}\times U(1{)}_X$, in which a vector-like fermion pair (${\zeta }_L$ and ${\zeta }_R$) charged under the $U(1{)}_{B-L}\times U(1{)}_X$ symmetry is introduced. Associated with the symmetry breaking of the gauge group $SU(2{)}_R\times U(1{)}_{B-L}\times U(1{)}_X$ down to the Standard Model (SM) hypercharge $U(1{)}_Y$, Majorana masses for ${\zeta }_{L,R}$ are generated and the lightest mass eigenstate plays a role of the dark matter (DM) in our universe by its communication with the SM particles through a new neutral gauge boson "$X$". We consider various phenomenological constraints of this DM scenario, such as the observed DM relic density, the LHC Run-2 constraints from the search for a narrow resonance, and the perturbativity of the gauge couplings below the Planck scale. Combining all constraints, we identify the allowed parameter region which turns out to be very narrow. A significant portion of the currently allowed parameter region will be tested by the High-Luminosity LHC experiments.

   hep-phastro-ph.COhep-exJHEP(2021)·4 citations
6. 06*

   Two-gluon production of $\varphi$ and ${\eta }^{\prime }$ mesons in proton-proton collisions at high energies

   Anna Cisek🇵🇱 · Antoni Szczurek🇵🇱

   We discuss gluon-gluon mechanisms for production of mesons with hidden strangeness, such as ${\eta }^{\prime }$ and $\varphi$ meson, in proton-proton collisions at large energies. The $g^{\ast }{g}^{\ast }\to {\eta }^{\prime }$ and $g^{\ast }{g}^{\ast }\to \varphi g$ mechanisms are considered only and the corresponding cross sections are calculated in the $k_t$-factorization approach. The $F_{{\gamma }^{\ast }{\gamma }^{\ast }\to {\eta }^{\prime }}$ and $F_{g^{\ast }{g}^{\ast }\to {\eta }^{\prime }}$ form factors are calculated from quark-antiquark ${\eta }^{\prime }$ light-cone wave function including quark/antiquark transverse momenta. The result for two-photon transition form factor demonstrates that higher twists may survive even to large photon virtualities. The result is compared with the result of a recent leading-twist NLO analysis which uses phenomenological distribution amplitudes fitted to exclusive production of ${\eta }^{\prime }$ in $e^{+}{e}^{-}\to e^{+}{e}^{-}{\eta }^{\prime }$ reaction. We calculate transverse momentum distributions of both ${\eta }^{\prime }$ and $\varphi$ mesons in proton-proton collisions for RHIC and LHC energies. The results are compared to experimental data whenever available. The results of the Lund string model are shown for comparison for ${\eta }^{\prime }$ production at LHC energies. It seems that the two-gluon fusion is not the dominant mechanism for both $\varphi$ and ${\eta }^{\prime }$ production, although the situation for ${\eta }^{\prime }$, especially at larger energies, is less clear due to lack of experimental data.

   hep-phPRD(2021)·8 citations
7. 07*

   Searching for $Z^{\prime }$ bosons at the P2 experiment

   P. S. Bhupal Dev🇺🇸 · Werner Rodejohann🇩🇪 · Xun-Jie Xu🇧🇪 · Yongchao Zhang🇨🇳

   The P2 experiment aims at high-precision measurements of the parity-violating asymmetry in elastic electron-proton and electron-${}^{12}$C scatterings with longitudinally polarized electrons. We discuss here the sensitivity of P2 to new physics mediated by an additional neutral gauge boson $Z^{\prime }$ of a new $U(1{)}^{\prime }$ gauge symmetry. If the charge assignment of the $U(1{)}^{\prime }$ is chiral, i.e., left- and right-handed fermions have different charges under $U(1{)}^{\prime }$, additional parity-violation is induced directly. On the other hand, if the $U(1{)}^{\prime }$ has a non-chiral charge assignment, additional parity-violation can be induced via mass or kinetic $Z$-$Z^{\prime }$ mixing. By comparing the P2 sensitivity to existing constraints, we show that in both cases P2 has discovery potential over a wide range of $Z^{\prime }$ mass. In particular, for chiral models, the P2 experiment can probe gauge couplings at the order of $10^{-5}$ when the $Z^{\prime }$ boson is light, and heavy $Z^{\prime }$ bosons up to 79 (90) TeV in the proton (${}^{12}$C) mode. For non-chiral models with mass mixing, the P2 experiment is sensitive to mass mixing angles smaller than roughly $10^{-4}$, depending on model details and gauge coupling magnitude.

   hep-phhep-exJHEP(2021)·20 citations
8. 08*

   $Cos(2{\varphi }_h)$ asymmetry in $J/\psi$ production in unpolarized $ep$ collision

   Raj Kishore🇮🇳 · Asmita Mukherjee🇮🇳 · Mariyah Siddiqah🇮🇳

   We present a calculation of the $cos(2{\varphi }_h)$ asymmetry in $J/\psi$ production in electron-proton collision at the future electron-ion collider (EIC), a useful channel to probe the gluon TMDs. We calculate the asymmetry at next-to-leading order (NLO) in ${\alpha }_s$ in the framework of generalized factorization. The dominating sub-process is ${\gamma }^{\ast }+g\to J/\psi +g$. The production of $J/\psi$ is calculated in the non-relativistic QCD(NRQCD) framework with the inclusion of both color singlet and color octet contributions. Numerical estimates of the $cos(2{\varphi }_h)$ asymmetry are given in the kinematical region to be accessed by the future EIC. The asymmetry depends on the parameterization of the gluon TMDs, as well as on the long distance matrix elements (LDMEs). We use both Gaussian-type parameterization and McLerran-Venugopalan model for the TMDs in the kinematical region of small-$x$, where the gluons play a dominant role. We obtain sizable asymmetry, which may be useful to probe the ratio of the linearly polarized and the unpolarized gluon distribution in the proton.

   hep-phPRD(2021)·19 citations
9. 09*

   Safety of Quark/Gluon Jet Classification

   Alexis Romero🇺🇸 · Daniel Whiteson🇺🇸 · Michael Fenton🇺🇸 · Julian Collado🇺🇸 · Pierre Baldi🇺🇸

   The classification of jets as quark- versus gluon-initiated is an important yet challenging task in the analysis of data from high-energy particle collisions and in the search for physics beyond the Standard Model. The recent integration of deep neural networks operating on low-level detector information has resulted in significant improvements in the classification power of quark/gluon jet tagging models. However, the improved power of such models trained on simulated samples has come at the cost of reduced interpretability, raising concerns about their reliability. We elucidate the physics behind quark/gluon jet classification decisions by comparing the performance of networks with and without constraints of infrared and collinear safety, and identify the nature of the unsafe information by revealing the energy and angular dependence of the learned models. This in turn allows us to approximate the performance of the low-level networks (by 99\% or higher) using equivalent sets of interpretable high-level observables, which can be used to probe the fidelity of the simulated samples and define systematic uncertainties.

   hep-phhep-ex26 citations
10. 10*

    Baryonic content of the pion

    Pablo Sanchez-Puertas🇪🇸 · Enrique Ruiz Arriola🇪🇸 · Wojciech Broniowski🇵🇱

    The baryon form factor of charged pions arises since isospin symmetry is broken with unequal up and down quark masses, $m_d>m_u$, as well as electromagnetic effects. We obtain estimates for this basic property in two phenomenological ways: from simple constituent quark models, as well as from fitting the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ data. All our methods yield the result that the baryon mean square radius, extracted from the slope of the form factor, is positive for ${\pi }^{+}$, hence a picture where the outer region has a net baryon, and the inner region a net antibaryon density, both compensating each other such that the total baryon number is zero. For ${\pi }^{-}$ the effect is equal and opposite. We estimate the corresponding mean squared baryon radius as $⟨r^2{⟩}_B^{{\pi }^{+}}=(0.03-0.04\mathrm{fm}{)}^2$.

    hep-phPLB(2021)·5 citations
11. 11*

    Spin polarization induced by the hydrodynamic gradients

    Shuai Y. F. Liu🇨🇳 · Yi Yin🇨🇳

    We systematically analyze the effects of the derivatives of the hydrodynamic fields on axial Wigner function that describes the spin polarization vector in phase space. We have included all possible first-order derivative contributions that are allowed by symmetry and compute the associated transport functions at one-loop using the linear response theory. In addition to reproducing known effects due to the temperature gradient and vorticity, we have identified a number of potentially significant contributions that are overlooked previously. In particular, we find that the shear strength, the symmetric and traceless part of the flow gradient, will induce a quadrupole for spin polarization in the phase space. We refer to this novel effect as the shear-induced polarization (SIP). Our results, together with hydrodynamic gradients obtained from hydrodynamic simulations, can be employed as a basis for the interpretation of the $\Lambda$ (anti-$\Lambda$) spin polarization measurement in heavy-ion collisions.

    hep-phnucl-thJHEP(2021)·163 citations
12. 12*

    Lotty -- The loop-tree duality automation

    William J. Torres Bobadilla🇩🇪

    Elaborating on the novel formulation of the loop-tree duality, we introduce the Mathematica package Lotty that automates the latter at multi-loop level. By studying the features of Lotty and recalling former studies, we discuss that the representation of any multi-loop amplitude can be brought in a form, at integrand level, that only displays physical information, which we refer to as the causal representation of multi-loop Feynman integrands. In order to elucidate the role of Lotty in this automation, we recall results obtained for the calculation of the dual representation of integrands up-to four loops. Likewise, within Lotty framework, we provide support to the all-loop causal representation recently conjectured by the same author. The numerical stability of the integrands generated by Lotty is studied in two-loop planar and non-planar topologies, where a numerical integration is performed and compared with known results.

    hep-phhep-thEPJC(2021)·47 citations
13. 13*

    Dark Energy and the Time Dependence of Fundamental Particle Constants

    Bodo Lampe🇩🇪

    The cosmic time dependencies of $G$, $\alpha$, $\hslash$ and of Standard Model parameters like the Higgs vev and elementary particle masses are studied in the framework of a new dark energy interpretation. Due to the associated time variation of rulers, many effects turn out to be invisible. However, a rather large time dependence is claimed to arise in association with dark energy measurements, and smaller ones in connection with the Standard Model.

    hep-phgr-qcPhysics(2021)·2 citations
14. 14*

    Constraining Ultra-light Axions with Galaxy Cluster Number Counts

    Johannes Diehl🇩🇪 · Jochen Weller🇩🇪

    In this paper we investigate the potential of current and upcoming cosmological surveys to constrain the mass and abundance of ultra-light axion (ULA) cosmologies with galaxy cluster number counts. ULAs, sometimes also referred to as Fuzzy Dark Matter, are well-motivated in many theories beyond the Standard Model and could potentially solve the $\Lambda$CDM small-scale crisis. Galaxy cluster counts provide a robust probe of the formation of structures in the Universe. Their distribution in mass and redshift is strongly sensitive to the underlying linear matter perturbations. In this forecast paper we explore two scenarios, firstly an exclusion limit on axion mass given a no-axion model and secondly constraints on an axion model. With this we obtain lower limits on the ULA mass on the order of $m_a\gtrsim 10^{-24}$ eV. However, this result depends heavily on the mass of the smallest reliably observable clusters for a given survey. Cluster counts, like many other cosmological probes, display an approximate degeneracy in the ULA mass vs. abundance parameter space, which is dependent on the characteristics of the probe. These degeneracies are different for other cosmological probes. Hence galaxy cluster counts might provide a complementary window on the properties of ultra-light axions.

    ↳ astro-ph.COhep-phJCAP(2021)·6 citations
15. 15*

    Dark matter searches using accelerometer-based networks

    Nataniel L. Figueroa🇩🇪 · Dmitry Budker🇩🇪 · Ernst M. Rasel🇩🇪

    Dark matter is one of the biggest open questions in physics today. It is known that it interacts gravitationally with luminous matter, so accelerometer-based searches are inherently interesting. In this article we present recent (and future) searches for dark matter candidates such as feebly interacting matter trapped inside the Earth, scalar-matter domain walls and axion quark nuggets, with accelerometer networks and give an outlook of how new atomic-interferometry-based accelerometer networks could support dark matter searches.

    ↳ astro-ph.COhep-phQuantum Sci.Technol.(2021)·18 citations
16. 16*

    ${\Lambda }_b\to {\Lambda }_c^{\ast }(2595,2625){\ell }^{-}\bar{\nu }$ form factors from lattice QCD

    Stefan Meinel🇺🇸 · Gumaro Rendon🇺🇸

    We present the first lattice-QCD determination of the form factors describing the semileptonic decays ${\Lambda }_b\to {\Lambda }_c^{\ast }(2595){\ell }^{-}\bar{\nu }$ and ${\Lambda }_b\to {\Lambda }_c^{\ast }(2625){\ell }^{-}\bar{\nu }$, where the ${\Lambda }_c^{\ast }(2595)$ and ${\Lambda }_c^{\ast }(2625)$ are the lightest charm baryons with $J^P={\frac{1}{2}}^{-}$ and $J^P={\frac{3}{2}}^{-}$, respectively. These decay modes provide new opportunities to test lepton flavor universality and also play an important role in global analyses of the strong interactions in $b\to c$ semileptonic decays. We determine the full set of vector, axial vector, and tensor form factors for both decays, but only in a small kinematic region near the zero-recoil point. The lattice calculation uses three different ensembles of gauge-field configurations with $2+1$ flavors of domain-wall fermions, and we perform extrapolations of the form factors to the continuum limit and physical pion mass. We present Standard-Model predictions for the differential decay rates and angular observables. In the kinematic region considered, the differential decay rate for the ${\frac{1}{2}}^{-}$ final state is found to be approximately 2.5 times larger than the rate for the ${\frac{3}{2}}^{-}$ final state. We also test the compatibility of our form-factor results with zero-recoil sum rules.

    ↳ hep-lathep-exhep-phPRD(2021)·35 citations
17. 17*

    Density dependence of the quark condensate in isospin-asymmetric nuclear matter

    Stephan Hübsch🇯🇵 · Daisuke Jido🇯🇵

    We compute the density dependence of the quark condensate and how it changes under the influence of isospin-asymmetric nuclear matter. This is achieved by the calculation of the relevant Feynman diagrams using in-medium chiral perturbation theory. We find that the absolute value of the quark condensate decreases in nuclear matter by around 35% at normal nuclear density, in agreement with previous model-independent calculations. We also present an quantitative estimation of the difference of up- and down quark in-medium condensates.

    ↳ nucl-thhep-phPRC(2021)·9 citations
18. 18*

    Inverse Higgs phenomena as duals of holonomic constraints

    Ben Gripaios🇬🇧 · Joseph Tooby-Smith🇬🇧

    The inverse Higgs phenomenon, which plays an important rôle in physical systems with Goldstone bosons (such as the phonons in a crystal) involves nonholonomic mechanical constraints. By formulating field theories with symmetries and constraints in a general way using the language of differential geometry, we show that many examples of constraints in inverse Higgs phenomena fall into a special class, which we call coholonomic constraints, that are dual (in the sense of category theory) to holonomic constraints. Just as for holonomic constraints, systems with coholonomic constraints are equivalent to unconstrained systems (whose degrees of freedom are known as essential Goldstone bosons), making it easier to study their consistency and dynamics. The remaining examples of inverse Higgs phenomena in the literature require the dual of a slight generalisation of a holonomic constraint, which we call (co)meronomic. Our formalism simplifies and clarifies the many ad hoc assumptions and constructions present in the literature. In particular, it identifies which are necessary and which are merely convenient. It also opens the way to studying much more general dynamical examples, including systems which have no well-defined notion of a target space.

    ↳ hep-thhep-phmath-phmath.MPJ.Phys.A(2022)·1 citation
19. 19*

    Light Meson Physics at BESIII

    Shuangshi Fang🇨🇳

    Studies of light meson decays are important tools to perform precision tests of the effective field theories, determine transition form factors, and test fundamental symmetries. With very high statistics data samples, the BESIII experiment provides a unique laboratory for light meson studies and is contributing significantly to a variety of these investigations. A brief review of recent progress in light meson decay studied at the BESIII experiment, including detailed studies of common decay dynamics, searches for rare/forbidden decays and new particles, is presented. Finally, together with descriptions of different experimental techniques, prospects for future studies of light mesons are discussed in some detail.

    ↳ hep-exhep-phNatl.Sci.Rev.(2021)·9 citations
20. 20*

    Warp factor and the gravitational wave spectrum

    David Andriot🇦🇹 · Paul Marconnet🇫🇷 · Dimitrios Tsimpis🇫🇷

    A distinct signature of compact extra dimensions would be a Kaluza-Klein tower of gravitational waves. Motivated by this prospect, we compute the corresponding spectrum on a warped toroidal background. We evaluate in particular the impact of the warp factor on the spectrum. To that end, we use the complete warp factor H of standard string compactifications, generated by D-branes and orientifolds, thus connecting to recent works on stringy de Sitter constructions. The problematic region close to an orientifold where H < 0 leads to unphysical tachyonic modes in the spectrum. We develop tools that overcome this difficulty and lead to a tachyon-free spectrum. We show, in particular, that the warp factor can lower the first Kaluza-Klein mass by at least 69%.

    ↳ hep-thastro-ph.COastro-ph.HEgr-qc+1JCAP(2021)·23 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.