Mon·May 24, 2021Monday·May 24, 2021

1. 01*

   Deep-Learned Event Variables for Collider Phenomenology

   Doojin Kim🇺🇸 · Kyoungchul Kong🇺🇸 · Konstantin T. Matchev🇺🇸 · Myeonghun Park🇰🇷 · Prasanth Shyamsundar🇺🇸

   The choice of optimal event variables is crucial for achieving the maximal sensitivity of experimental analyses. Over time, physicists have derived suitable kinematic variables for many typical event topologies in collider physics. Here we introduce a deep learning technique to design good event variables, which are sensitive over a wide range of values for the unknown model parameters. We demonstrate that the neural networks trained with our technique on some simple event topologies are able to reproduce standard event variables like invariant mass, transverse mass, and stransverse mass. The method is automatable, completely general, and can be used to derive sensitive, previously unknown, event variables for other, more complex event topologies.

   hep-phcs.LGhep-exphysics.data-anPRD(2023)·12 citations
2. 02*

   Azimuthal correlations in diffractive scattering at the Electron-Ion Collider

   Adrian Dumitru🇺🇸 · Heikki Mäntysaari🇫🇮 · Risto Paatelainen🇫🇮 · Kaushik Roy🇩🇪 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸

   We calculate azimuthal correlations between the exclusively produced vector meson and the scattered electron in Deep Inelastic Scattering processes at the future Electron-Ion Collider (EIC). We identify "kinematical" and "intrinsic" contributions to these correlations, and show that the correlations are sensitive to the non-trivial correlations in the gluon distribution of the target. Realistic predictions at the EIC kinematics are provided using two different approaches to describe the dipole-proton interaction at relatively small $x$.

   hep-phnucl-thSciPost Phys.Proc.(2022)·5 citations
3. 03*

   Top quark electroweak interactions

   Ken Mimasu🇬🇧

   I discuss how modified EW interactions lead to energy growth in $2\to 2$ scattering amplitudes and how the framework of the Standard Model Effective Field Theory can be used in conjunction with the Goldstone boson equivalence theorem to better understand the origin of such unitarity violating behaviour. I quantify how applications in constraining top quark electroweak couplings are especially motivated due to our relatively poor understanding of them. I present some highlights of a systematic study of energy growth in EW top scattering amplitudes with a focus on how such effects can be searched for in realistic collider processes, demonstrating some promising avenues for future study.

   hep-ph1 citation
4. 04*

   Energy-momentum tensor of the nucleon on the light front: Abel tomography case

   June-Young Kim🇩🇪 · Hyun-Chul Kim🇰🇷

   We investigate the two-dimensional energy-momentum-tensor (EMT) distributions of the nucleon on the light front, using the Abel transforms of the three-dimensional EMT ones. We explicitly show that the main features of all EMT distributions are kept intact in the course of the Abel transform. We also examine the equivalence between the global and local conditions for the nucleon stability in the three-dimensional Breit frame and in the two-dimensional transverse plane on the light front. We also discuss the two-dimensional force fields inside a nucleon on the light front.

   hep-phhep-exhep-latPRD(2021)·35 citations
5. 05*

   Gamma Factory Searches for Extremely Weakly-Interacting Particles

   Sreemanti Chakraborti🇮🇳 · Jonathan L. Feng🇺🇸 · James K. Koga🇯🇵 · Mauro Valli🇺🇸

   The Gamma Factory is a proposal to back-scatter laser photons off a beam of partially-stripped ions at the LHC, producing a beam of $\sim 10$ MeV to $1$ GeV photons with intensities of $10^{16}$ to $10^{18}{\text{s}}^{-1}$. This implies $\sim 10^{23}$ to $10^{25}$ photons on target per year, many orders of magnitude greater than existing accelerator light sources and also far greater than all current and planned electron and proton fixed target experiments. We determine the Gamma Factory's discovery potential through "dark Compton scattering," $\gamma e\to eX$, where $X$ is a new, weakly-interacting particle. For dark photons and other new gauge bosons with masses in the 1~to~100 MeV range, the Gamma Factory has the potential to discover extremely weakly-interacting particles with just a few hours of data and will probe couplings as low as $\sim 10^{-9}$ with a year of running. The Gamma Factory therefore may probe couplings lower than all other terrestrial experiments and is highly complementary to astrophysical probes. We outline the requirements of an experiment to realize this potential and determine the sensitivity reach for various experimental configurations.

   hep-phhep-exPRD(2021)·18 citations
6. 06*

   Challenges for heavy QCD axion inflation

   Fuminobu Takahashi🇯🇵 · Wen Yin🇯🇵

   We examine the theoretical possibility for the heavy QCD axion to induce slow-roll inflation while solving the strong CP problem through the Peccei-Quinn mechanism. If the cancellation between contributions from a small-size instanton and another Peccei-Quinn symmetry breaking occurs with high accuracy, the potential can be flattened enough near its maximum to achieve hilltop inflation. This comes at the cost of severe fine-tuning of their relative size and phase, but it also allows us to relate the high quality problem of the Peccei-Quinn symmetry to the fine-tuning problem of the hilltop inflation. There are two classes of such axion hilltop inflation, each giving a different relation between the axion mass at the minimum and the decay constant. The first class predicts the relation $m_{\varphi }\sim 10^{-6}{f}_{\varphi }$, and the axion can decay via the gluon coupling and reheat the universe. Most of the predicted parameter region will be covered by various experiments such as CODEX, DUNE, FASER, LHC, MATHUSLA, and NA62 where the production and decay proceed through the same coupling that induced reheating. The second class predicts the relation $m_{\varphi }\sim 10^{-6}{f}_{\varphi }^2/M_{\mathrm{pl}}$. In this case, the axion mass is much lighter than in the previous case, and one needs another mechanism for successful reheating. The viable decay constant is restricted to be $10^8\mathrm{GeV}\lesssim f_{\varphi }\lesssim 10^{10}$GeV, which will be probed by future experiments on the electric dipole moment of nucleons. In both cases, requiring the axion hilltop inflation results in the strong CP phase that is close to zero.

   hep-phgr-qchep-exJCAP(2021)·41 citations
7. 07*

   Probing the Particle Spectrum of Nature with Evaporating Black Holes

   Michael J. Baker🇦🇺 · Andrea Thamm🇦🇺

   Photons radiated from an evaporating black hole in principle provide complete information on the particle spectrum of nature up to the Planck scale. If an evaporating black hole were to be observed, it would open a unique window onto models beyond the Standard Model of particle physics. To demonstrate this, we compute the limits that could be placed on the size of a dark sector. We find that observation of an evaporating black hole at a distance of 0.01 parsecs could probe dark sector models containing one or more copies of the Standard Model particles, with any mass scale up to 100 TeV.

   hep-phastro-ph.HESciPost Phys.(2022)·55 citations
8. 08*

   Reframing Jet Physics with New Computational Methods

   Kyle Cranmer🇺🇸 · Matthew Drnevich🇺🇸 · Sebastian Macaluso🇺🇸 · Duccio Pappadopulo🇺🇸

   We reframe common tasks in jet physics in probabilistic terms, including jet reconstruction, Monte Carlo tuning, matrix element - parton shower matching for large jet multiplicity, and efficient event generation of jets in complex, signal-like regions of phase space. We also introduce Ginkgo, a simplified, generative model for jets, that facilitates research into these tasks with techniques from statistics, machine learning, and combinatorial optimization. We review some of the recent research in this direction that has been enabled with Ginkgo. We show how probabilistic programming can be used to efficiently sample the showering process, how a novel trellis algorithm can be used to efficiently marginalize over the enormous number of clustering histories for the same observed particles, and how dynamic programming, A* search, and reinforcement learning can be used to find the maximum likelihood clustering in this enormous search space. This work builds bridges with work in hierarchical clustering, statistics, combinatorial optmization, and reinforcement learning.

   hep-phhep-exphysics.data-anEPJ Web Conf.(2021)·12 citations
9. 09*

   Positive magnetoresistance induced by hydrodynamic fluctuations in chiral media

   Noriyuki Sogabe🇨🇳 · Naoki Yamamoto🇯🇵 · Yi Yin🇨🇳

   We analyze the combined effects of hydrodynamic fluctuations and chiral magnetic effect (CME) for a chiral medium in the presence of a background magnetic field. Based on the recently developed non-equilibrium effective field theory, we show fluctuations give rise to a CME-related positive contribution to magnetoresistance, while the early studies without accounting for the fluctuations find a CME-related negative magnetoresistance. At zero axial relaxation rate, the fluctuations contribute to the transverse conductivity in addition to the longitudinal one.

   ↳ hep-thcond-mat.str-elhep-phnucl-thJHEP(2021)·8 citations
10. 10*

    Updated measurement of $R_K$ at LHCb

    Davide Lancierini🇨🇭

    In the Standard Model of particle physics, charged leptons of different flavour couple to the electroweak force carriers with the same interaction strength. This property, known as lepton flavour universality, was found to be consistent with experimental evidence in a wide range of particle decays. Lepton flavour universality can be tested by comparing branching fractions in ratios such as $R_K=\mathcal{B}(B^{+}\to K^{+}{\mu }^{+}{\mu }^{-})/\mathcal{B}(B^{+}\to K^{+}{e}^{+}{e}^{-})$. This observable is measured using proton-proton collision data recorded with the LHCb detector at CERN's Large Hadron Collider corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$. For a dilepton invariant mass range of $q^2\in [1.1,6.0]\mathrm{Ge}{\mathrm{V}}^2$, the measured value of $R_K=0.846{}_{-0.039}^{+0.042}{}_{-0.012}^{+0.013}$, where the first uncertainty is statistic and the second systematic, is in tension with the Standard Model predicted value at the $3.1\sigma$ level raising evidence for lepton flavour universality violation in $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays.

    ↳ hep-exhep-ph3 citations
11. 11*

    Quark Nova with the Producing of Color-Flavor Locked Quark Matter

    Jia-Rui Guo🇨🇳

    In this paper, we suggest that the process in quark nova explosion may exist widely in various kinds of supernova, although it only happens in a small part in the core in most cases. And the contribution to the energy releasing of whole supernova explosion can also be provided by QCD interacting term. In this way we derive a general equation of energy quantity to be released in quark nova process related to several parameters. After quark nova explosion process, the remnant can be a quark star, or a neutron star with quark matter core if this process only happens in a small part inside the compact star instead of a "full" quark nova. We will also use a more generalized approach to analyse the strangelets released from quark nova and will draw a possible interpretation of why effects caused by strangelets have not been observed yet. Our result suggests that the ordinary matter can only spontaneously transform into strange quark matter by crushing them into high pressure under the extreme condition in compact star, although generally the reaction would really be exergonic.

    ↳ nucl-thhep-ph0 citations
12. 12*

    Consistency tests of $\Lambda$CDM from the early integrated Sachs-Wolfe effect: Implications for early-time new physics and the Hubble tension

    Sunny Vagnozzi🇬🇧

    New physics increasing the expansion rate just prior to recombination is among the least unlikely solutions to the Hubble tension, and would be expected to leave an important signature in the early Integrated Sachs-Wolfe (eISW) effect, a source of Cosmic Microwave Background (CMB) anisotropies arising from the time-variation of gravitational potentials when the Universe was not completely matter dominated. Why, then, is there no clear evidence for new physics from the CMB alone, and why does the $\Lambda$CDM model fit CMB data so well? These questions and the vastness of the Hubble tension theory model space motivate general consistency tests of $\Lambda$CDM. I perform an eISW-based consistency test of $\Lambda$CDM introducing the parameter $A_{\mathrm{eISW}}$, which rescales the eISW contribution to the CMB power spectra. A fit to Planck CMB data yields $A_{\mathrm{eISW}}=0.988\pm 0.027$, in perfect agreement with the $\Lambda$CDM expectation $A_{\mathrm{eISW}}=1$, and posing an important challenge for early-time new physics, which I illustrate in a case study focused on early dark energy (EDE). I explicitly show that the increase in ${\omega }_c$ needed for EDE to preserve the fit to the CMB, which has been argued to worsen the fit to weak lensing and galaxy clustering measurements, is specifically required to lower the amplitude of the eISW effect, which would otherwise exceed $\Lambda$CDM's prediction by $\approx 20\%$: this is a generic problem beyond EDE and likely applying to most models enhancing the expansion rate around recombination. Early-time new physics models invoked to address the Hubble tension are therefore faced with the significant challenge of making a similar prediction to $\Lambda$CDM for the eISW effect, while not degrading the fit to other measurements in doing so.

    ↳ astro-ph.COgr-qchep-phPRD(2021)·246 citations
13. 13*

    de Sitter Decays to Infinity

    Patrick Draper🇺🇸 · Isabel Garcia Garcia🇺🇸 · Benjamin Lillard🇺🇸

    Bubbles of nothing are a class of vacuum decay processes present in some theories with compactified extra dimensions. We investigate the existence and properties of bubbles of nothing in models where the scalar pseudomoduli controlling the size of the extra dimensions are stabilized at positive vacuum energy, which is a necessary feature of any realistic model. We map the construction of bubbles of nothing to a four-dimensional Coleman-De Luccia problem and establish necessary conditions on the asymptotic behavior of the scalar potential for the existence of suitable solutions. We perform detailed analyses in the context of five-dimensional theories with metastable ${\text{dS}}_4\times S^1$ vacua, using analytic approximations and numerical methods to calculate the decay rate. We find that bubbles of nothing sometimes exist in potentials with no ordinary Coleman-De Luccia decay process, and that in the examples we study, when both processes exist, the bubble of nothing decay rate is typically faster. Our methods can be generalized to other stabilizing potentials and internal manifolds.

    ↳ hep-thgr-qchep-phJHEP(2021)·20 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.