Wed·Jul 29, 2020Wednesday·July 29, 2020

1. 01*

   Indirect searches for dark matter bound state formation and level transitions

   Iason Baldes🇧🇪 · Francesca Calore🇫🇷 · Kalliopi Petraki🇫🇷 · Vincent Poireau🇫🇷 · Nicholas L. Rodd🇺🇸

   Indirect searches for dark matter (DM) have conventionally been applied to the products of DM annihilation or decay. If DM couples to light force carriers, however, it can be captured into bound states via dissipation of energy that may yield detectable signals. We extend the indirect searches to DM bound state formation and transitions between bound levels, and constrain the emission of unstable dark photons. Our results significantly refine the predicted signal flux that could be observed in experiments. As a concrete example, we use Fermi-LAT dwarf spheroidal observations to obtain constraints in terms of the dark photon mass and energy which we use to search for the formation of stable or unstable bound states.

   hep-phastro-ph.HESciPost Phys.(2020)·26 citations
2. 02*

   Neutron's Dark Secret

   Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸

   The existing discrepancy between neutron lifetime measurements in bottle and beam experiments has been interpreted as a sign of the neutron decaying to dark particles. We summarize the current status of this proposal, including a discussion of particle physics models involving such a portal between the Standard Model and a baryonic dark sector. We also review further theoretical developments around this idea and elaborate on the prospects for verifying the neutron dark decay hypothesis in current and upcoming experiments.

   hep-phMod.Phys.Lett.A(2020)·42 citations
3. 03*

   Heavy Particle Jet Identification with Zest

   Ankita Budhraja🇮🇳 · Ambar Jain🇮🇳

   We introduce a new jet observable {\em zest} defined on exclusively constructed jets and study its potential to discriminate jets originated from Standard Model heavy particles like $W,Z$ bosons and top quark from gluon initiated jets. Zest exhibits properties such as boost invariance, stability against global color exchange among partons, and inclusion or exclusion of a few soft particles in the jet. We also observe that for gluon jets, zest distribution is mostly insensitive to the jet mass. These properties make zest a suitable candidate for vetoing gluon jets at the colliders. Zest when used in conjunction with other substructure observables that are uncorrelated to it can further improve gluon jet veto. We generalize zest and show that in one limit it is synonymous to particle multiplicity and in the other limit, it projects only the leading particle. Optimization on the parameter of generalized zest further improves the discrimination ability of the observable. We find that for the top quark-initiated jets, the discrimination provided by generalized zest is in close comparison with a class of machine learning-based top taggers. We propose that studying other non-linear infrared and collinear unsafe observables may help in unveiling the hidden physics of machine learning-based observables.

   hep-phPRD(2020)·0 citations
4. 04*

   Precise Calculation of the Decay Rate of False Vacuum with Multi-Field Bounce

   So Chigusa🇯🇵 · Takeo Moroi🇯🇵 · Yutaro Shoji🇯🇵

   We study the decay rate of a false vacuum in gauge theory at the one-loop level. We pay particular attention to the case where the bounce consists of an arbitrary number of scalar fields. With a multi-field bounce, which has a curved trajectory in the field space, the mixing among the gauge fields and the scalar fields evolves along the path of the bounce in the field space and the one-loop calculation of the vacuum decay rate becomes complicated. We consider the one-loop contribution to the decay rate with an arbitrary choice of the gauge parameter, and obtain a gauge invariant expression of the vacuum decay rate. We also give proper treatments of gauge zero modes and renormalization.

   hep-phhep-thJHEP(2020)·8 citations
5. 05*

   Neutrinos masses in a supersymmtric model with exotic right-handed neutrinos in Global $(B-L)$ Symmetry

   M. C. Rodriguez🇧🇷

   We consider an Supersymmetric extension of the Standard Model with some extra Higgs doublets and a global $(B-L)$, where $B$ and $L$ are the usual baryonic and lepton number respectivelly, and ${\mathcal{Z}}_3\otimes {\mathcal{Z}}_3^{\prime }$ symmetries of the non-SUSY model presented at [1]..

   hep-phInt.J.Mod.Phys.A(2021)·2 citations
6. 06*

   Light charged pion in ultra-strong magnetic field

   Jingyi Chao🇨🇳 · Yu-Xin Liu🇨🇳 · Lei Chang🇨🇳

   In this work, the mass of charged pions is investigated in the presence of background magnetic fields stronger than the energy scale of QCD. We introduce an anomaly magnetic momentum term in the Dirac equation and obtain the quark propagator as consequence. We find a novel finite Landau level, denoted as $tl$LL, becoming dominant rather than the conventional lowest Landau level. We examine that, due to the shifting of Landau level, it drives a mass decreasing around $eB\sim 0.8{\mathrm{GeV}}^2$ for charged pions and their masses drastically limit to the neutral one at ultra-strong magnetic field, $eB\sim 1.6{\mathrm{GeV}}^2$, which is consistent with the recent lattice simulation.

   hep-phnucl-th11 citations
7. 07*

   Quarkonia formation in a holographic gravity-dilaton background describing QCD thermodynamics

   R. Zöllner🇩🇪 · B. Kampfer

   A holographic model of probe quarkonia is presented, where the dynamical gravity-dilaton background is adjusted to the thermodynamics of 2 +1 flavor QCD with physical quark masses. The quarkonia action is modified to account for a systematic study of the heavy-quark mass dependence. We focus on the $J/\psi$ and ${\rm Y}$ spectral functions and relate our model to heavy quarkonia formation as a special aspect of hadron phenomenology in heavy-ion collisions at LHC.

   hep-phhep-thParticles(2021)·13 citations
8. 08*

   High Energy Leptonic Collisions and Electroweak Parton Distribution Functions

   Tao Han🇺🇸 · Yang Ma🇺🇸 · Keping Xie🇺🇸

   In high-energy leptonic collisions well above the electroweak scale, the collinear splitting mechanism of the electroweak gauge bosons becomes the dominant phenomena via the initial state radiation and the final state showering. We point out that at future high-energy lepton colliders, such as a multi-TeV muon collider, the electroweak parton distribution functions (EW PDFs) should be adopted as the proper description for partonic collisions of the initial states. The leptons and electroweak gauge bosons are the EW partons, that evolve according to the unbroken Standard Model (SM) gauge group and that effectively resum potentially large collinear logarithms. We present a formalism for the EW PDFs at the Next-to-Leading-Log (NLL) accuracy. We calculate semi-inclusive cross sections for some important SM processes at a future multi-TeV muon collider. We conclude that it is appropriate to adopt the EW PDF formalism for future high-energy lepton colliders.

   hep-phhep-exPRD(2021)·173 citations
9. 09*

   Crunching Dilaton, Hidden Naturalness

   Csaba Csaki🇺🇸 · Raffaele Tito D'Agnolo🇫🇷 · Michael Geller🇮🇱 · Ameen Ismail🇺🇸

   We introduce a new approach to the Higgs naturalness problem, where the value of the Higgs mass is tied to cosmic stability and the possibility of a large observable Universe. The Higgs mixes with the dilaton of a CFT sector whose true ground state has a large negative vacuum energy. If the Higgs VEV is non-zero and below $\mathcal{O}(\mathrm{TeV})$, the CFT also admits a second metastable vacuum, where the expansion history of the Universe is conventional. As a result, only Hubble patches with unnaturally small values of the Higgs mass support inflation and post-inflationary expansion, while all other patches rapidly crunch. The elementary Higgs VEV driving the dilaton potential is the essence of our new solution to the hierarchy problem. The main experimental prediction is a light dilaton field in the 0.1-10 GeV range that mixes with the Higgs. Part of the viable parameter space has already been probed by measurements of rare B-meson decays, and the rest will be fully explored by future colliders and experiments searching for light, weakly-coupled particles.

   hep-phPRL(2021)·59 citations
10. 10*

    ABCDisCo: Automating the ABCD Method with Machine Learning

    Gregor Kasieczka🇩🇪 · Benjamin Nachman🇺🇸 · Matthew D. Schwartz🇺🇸 · David Shih🇺🇸

    The ABCD method is one of the most widely used data-driven background estimation techniques in high energy physics. Cuts on two statistically-independent classifiers separate signal and background into four regions, so that background in the signal region can be estimated simply using the other three control regions. Typically, the independent classifiers are chosen "by hand" to be intuitive and physically motivated variables. Here, we explore the possibility of automating the design of one or both of these classifiers using machine learning. We show how to use state-of-the-art decorrelation methods to construct powerful yet independent discriminators. Along the way, we uncover a previously unappreciated aspect of the ABCD method: its accuracy hinges on having low signal contamination in control regions not just overall, but relative to the signal fraction in the signal region. We demonstrate the method with three examples: a simple model consisting of three-dimensional Gaussians; boosted hadronic top jet tagging; and a recasted search for paired dijet resonances. In all cases, automating the ABCD method with machine learning significantly improves performance in terms of ABCD closure, background rejection and signal contamination.

    hep-phhep-exphysics.data-anPRD(2021)·96 citations
11. 11*

    Model Independent Bounds on the Non-Oscillatory Explanations of the MiniBooNE Excess

    Vedran Brdar🇩🇪 · Oliver Fischer🇩🇪 · Alexei Yu. Smirnov🇩🇪

    We consider the non-oscillatory explanations of the low energy excess of events detected by MiniBooNE. We present a systematic search for phenomenological scenarios based on new physics which can produce the excess. We define scenarios as series of transitions and processes which connect interactions of accelerated protons in target with single shower events in the MiniBooNE detector. The key elements of the scenarios are production and decay of new light $\mathcal{O}(\text{keV}-100\text{MeV})$ particles (fermions or/and bosons). We find about $20$ scenarios with minimal possible number of new particles and interaction points. In practice, they are all reduced to few generic scenarios and in this way we develop the effective theory of the MiniBooNE excess. We consider tests of the scenarios with near or close detectors in neutrino experiments T2K ND280, NO$\nu$A, MINER$\nu$A as well as in NOMAD and PS191. The scenarios immediately connect the MiniBooNE excess and expected numbers of new physics events in these detectors. We compute the expected numbers of events as functions of lifetimes and masses of new particles and confront them with the corresponding experimental bounds. We indicate scenarios that are excluded or strongly disfavored by one or several experiments. Given our general approach, this work can also be regarded as the effective theory of new physics at accelerator based neutrino experiments, being relevant for future projects such as DUNE.

    hep-phhep-exPRD(2021)·36 citations
12. 12*

    Radiative neutrino masses and exotic right-handed neutrinos

    A. C. B. Machado🇧🇷 · J. Montaño🇲🇽 · V. Pleitez🇧🇷 · M. C. Rodriguez🇧🇷

    We consider an extension of the standard electroweak model with three Higgs doublets and global $B-L$ and ${\mathbb{Z}}_2$ symmetries. Two of the scalar doublets are inert due to the ${\mathbb{Z}}_2$ symmetry. We calculated all the mass spectra in the scalar and lepton sectors and accommodate the leptonic mixing matrix as well. We also include an analysis of the scalar sector, showing that the potential is limited from below, and we obtain the masses of the scalar sector. Furthermore we consider the effects of the model on the anaomalous magnetic dipole of charged leptons and the $\mu \to e\gamma$ decay. We also present the SUSY version of the model with global $B-L$.

    hep-ph1 citation
13. 13*

    Parton distribution functions from lattice QCD using Bayes-Gauss-Fourier transforms

    Constantia Alexandrou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · Giovanni Iannelli (Univ. of Cyprus, Univ. of Rome Tor Vergata, Univ. of Humboldt Berlin and DESY-Zeuthen)🇨🇾 · Karl Jansen (DESY-Zeuthen)🇩🇪 · Floriano Manigrasso (Univ. of Cyprus, Univ. of Rome Tor Vergata and Univ. of Humboldt Berlin)🇨🇾

    We present a new method, based on Gaussian process regression, for reconstructing the continuous $x$-dependence of parton distribution functions (PDFs) from quasi-PDFs computed using lattice QCD. We examine the origin of the unphysical oscillations seen in current lattice calculations of quasi-PDFs and develop a nonparametric fitting approach to take the required Fourier transform. The method is tested on one ensemble of maximally twisted mass fermions with two light quarks. We find that with our approach oscillations of the quasi-PDF are drastically reduced. However, the final effect on the light-cone PDFs is small. This finding suggests that the deviation seen between current lattice QCD results and phenomenological determinations cannot be attributed solely on the Fourier transform.

    ↳ hep-lathep-phnucl-thPRD(2020)·37 citations
14. 14*

    Gravitational time dilation, free fall, and matter waves

    Anna Czarnecka🇨🇦 · Andrzej Czarnecki🇨🇦

    We demonstrate that a de Broglie wave of a particle in a gravitational field turns towards the region of a smaller gravitational potential, causing the particle to fall. This turning is caused by clocks running slower in the smaller potential. We use the analogy of ocean waves that are slower in shallower water and turn towards beaches. This approach explains the free fall qualitatively and quantitatively without postulating motion along geodesics and with only elementary algebra.

    ↳ gr-qchep-phhep-thAm.J.Phys.(2021)·4 citations
15. 15*

    Constraints on cosmological parameters from gamma-ray burst peak photon energy and bolometric fluence measurements and other data

    Narayan Khadka🇺🇸 · Bharat Ratra🇺🇸

    We use measurements of the peak photon energy and bolometric fluence of 119 gamma-ray bursts (GRBs) extending over the redshift range of $0.3399\le z\le 8.2$ to simultaneously determine cosmological and Amati relation parameters in six different cosmological models. The resulting Amati relation parameters are almost identical in all six cosmological models, thus validating the use of the Amati relation in standardizing these GRBs. The GRB data cosmological parameter constraints are consistent with, but significantly less restrictive than, those obtained from a joint analysis of baryon acoustic oscillation and Hubble parameter measurements.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2020)·81 citations
16. 16*

    Gamma-gamma collider with W_gg < 12 GeV based on the 17.5 GeV SC linac of the European XFEL

    V.I. Telnov (Institute of Nuclear Physics and Novosibirsk State Univ., Novosibirsk, Russia)🇷🇺

    We propose and demonstrate that a gamma-gamma collider with W_gg < 12 GeV can be added to the European XFEL with a minimal disruption to its main program. High-energy photons will be obtained by Compton scattering of 0.5 micron laser photons on the existing 17.5 GeV electron beams. Such a gamma-gamma collider would be an excellent place for the development and application of modern technologies: powerful lasers, optical cavities, superconducting linacs, and low-emittance electron sources -- as well as training the next generation of accelerator physicists and engineers. The physics program would include spectroscopy of C=+ resonances in various J^P states b\bar{b}, c\bar{c}, four-quark states, quark molecules and other exotica) in a mass range barely scratched by past and not covered by any current or planned experiments. Variable circular and linear polarizations will help in the determination of quantum numbers and measurement of polarization components of the gamma-gamma cross section (\sigma_\perp, \sigma_\parallel, \sigma_0, \sigma_2).

    ↳ physics.acc-phhep-exhep-phJINST(2020)·16 citations
17. 17*

    Single Extra Dimension from $\kappa$-Poincaré and Gauge Invariance

    Philippe Mathieu🇺🇸 · Jean-Christophe Wallet🇫🇷

    We show that $\kappa$-Poincaré invariant gauge theories on $\kappa$-Minkowski space with physically acceptable commutative (low energy) limit must be 5-d. The gauge invariance requirement of the action fixes the dimension of the $\kappa$-Minkowski space to $d=5$ and selects the unique twisted differential calculus with which the construction can be achieved. We characterize a BRST symmetry related to the 5-d noncommutative gauge invariance though the definition of a nilpotent operation, which is used to construct a gauge-fixed action. We also consider standard scenarios assuming (compactification of) flat extra dimension, for which the 5-d deformation parameter $\kappa$ can be viewed as the bulk 5-d Planck mass. We study physical properties of the resulting 4-d effective theories. Recent data from collider experiments require $\kappa \gtrsim \mathcal{O}(10^{13})\text{GeV}$. The use of standard test of in-vacuo dispersion relations of Gamma Ray Burst photons increases this lower bound by 4 orders of magnitude. The robustness of this bound is discussed in the light of possible new features of noncommutative causal structures.

    ↳ hep-thhep-phJHEP(2021)·22 citations
18. 18*

    The Atacama Cosmology Telescope: Delensed Power Spectra and Parameters

    Dongwon Han🇺🇸 · Neelima Sehgal🇺🇸 · Amanda MacInnis🇺🇸 · Alexander van Engelen🇺🇸 · Blake D. Sherwin🇬🇧 · Mathew S. Madhavacheril🇨🇦 · Simone Aiola🇺🇸 · Nicholas Battaglia🇺🇸 · James A. Beall🇺🇸 · Daniel T. Becker🇺🇸 · Erminia Calabrese🇬🇧 · Steve K. Choi🇺🇸 and 30 other authors

    We present LCDM cosmological parameter constraints obtained from delensed microwave background power spectra. Lensing maps from a subset of DR4 data from the Atacama Cosmology Telescope (ACT) are used to undo the lensing effect in ACT spectra observed at 150 and 98 GHz. At 150 GHz, we remove the lensing distortion with an effective efficiency of 30% (TT), 30% (EE), 26% (TE) and 20% (BB); this results in detections of the delensing effect at 8.7 sigma (TT), 5.1 sigma (EE), 2.6 sigma (TE), and 2.4 sigma (BB) significance. The combination of 150 and 98 GHz TT, EE, and TE delensed spectra is well fit by a standard LCDM model. We also measure the shift in best-fit parameters when fitting delensed versus lensed spectra; while this shift does not inform our ability to measure cosmological parameters, it does provide a three-way consistency check among the lensing inferred from the best-fit parameters, the lensing in the CMB power spectrum, and the reconstructed lensing map. This shift is predicted to be zero when fitting with the correct model since both lensed and delensed spectra originate from the same region of sky. Fitting with a LCDM model and marginalizing over foregrounds, we find that the shift in cosmological parameters is consistent with zero. Our results show that gravitational lensing of the microwave background is internally consistent within the framework of the standard cosmological model.

    ↳ astro-ph.COhep-phJCAP(2021)·44 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.