Fri·Feb 28, 2020Friday·February 28, 2020

1. 01*

   On gapped continuum resonance spectra

   Eugenio Megias🇪🇸 · Mariano Quiros🇪🇸

   In this work we study a warped five-dimensional (5D) model with ultraviolet (UV) and infrared (IR) branes, that solves the hierarchy problem with a fundamental 5D Planck scale $M$, and curvature parameter $k$, of the order of the 4D Planck mass $M_{\text{Planck}}\equiv 2.4\times 10^{15}$ TeV. The model exhibits a continuum of Kaluza-Klein (KK) modes with different mass gaps, at the TeV scale, for all fields. We have computed the Green's functions and spectral densities, and shown how the presence of a continuum KK spectrum can produce an enhancement in the cross section of some Standard Model processes. The metric is linear near the IR, in conformal coordinates, as in the linear dilaton and 5D clockwork models, for which $M\sim$ TeV. We also analyze a pure (continuum) linear dilaton scenario, solving the hierarchy problem with more conventional fundamental $M$ and $k$ scales of the order of $M_{\text{Planck}}$, and a continuum spectrum.

   hep-phhep-thInt.J.Mod.Phys.A(2021)·4 citations
2. 02*

   Pole analysis on the hadron spectroscopy of ${\Lambda }_b\to J/\Psi p{K}^{-}$

   Shi-Qing Kuang🇨🇳 · Ling-Yun Dai🇨🇳 · Xian-Wei Kang🇨🇳 · De-Liang Yao🇨🇳

   In this paper we study the $J/\Psi p$ spectroscopy in the process of ${\Lambda }_b\to J/\Psi p{K}^{-}$. The final state interactions of coupled channel $J/\Psi p$ ~-~ $\bar{D}{\Sigma }_c$~-~${\bar{D}}^{\ast }{\Sigma }_c$ are constructed based on K-matrix with the Chew-Mandelstam function. We build the ${\Lambda }_b\to J/\Psi p{K}^{-}$ amplitude according to the Au-Morgan-Pennington method. The event shape is fitted and the decay width of ${\Lambda }_b\to J/\Psi p{K}^{-}$ is used to constrain the parameters, too. With the amplitudes we extract out the poles and their residues. Our amplitude and pole analysis suggest that the $P_c(4312)$ should be $\bar{D}{\Sigma }_c$ molecule, the $P_c(4440)$ could be an S-wave compact pentaquark state, and the structure around $P_c(4457)$ is caused by the cusp effect. The future experimental measurement of the decays of ${\Lambda }_b\to \bar{D}{\Sigma }_c{K}^{-}$ and ${\Lambda }_b\to {\bar{D}}^{\ast }{\Sigma }_c{K}^{-}$ would further help to study the nature of these resonances.

   hep-phnucl-thEPJC(2020)·42 citations
3. 03*

   Higgs Inflation With Four-form Couplings

   C.J. Ouseph🇹🇼 · Kingman Cheung🇹🇼

   We consider a new inflationary model in which an antisymmetric tensor field $A_{\nu \rho \sigma }$ and its four-form field strength $F_{\mu \nu \rho \sigma }=4{\partial }_{[\mu }{A}_{\nu \rho \sigma ]}$ are coupled to the scalar sector of the standard model and to the Ricci scalar $\mathcal{R}$. The four-form field induces modifications to the Higgs self-coupling constant, the cosmological constant, and the non-minimal coupling constant, which results in the modification to the inflaton potential. We also show that there is no need for the Higgs-gravity coupling in the presence of four-form-gravity interaction, but still can produce the right amount of density perturbation for inflation.

   hep-phJ.Phys.G(2021)·2 citations
4. 04*

   An approach to the leading Regge pole

   S. D. Campos🇧🇷

   Neglecting spin effects, one introduces here a subtle approximation for the scattering angle, which allows the obtaining of a logarithmic leading Regge pole, consistent with the Froissart-Martin bound. A simple parameterization is also introduced for the proton-proton total cross section. Fitting procedures are implemented only for the highest energy experimental data available. The intercept for a linear approach is obtained, indicating the presence of a soft pomeron. The Tsallis entropy in the impact parameter space is calculated using the Regge pole formalism. This entropy depends on a free parameter, whose value implies the existence of a central or non-central maximum value for the entropy. The hollowness effect is discussed in terms of this parameter.

   hep-phhep-thPhys.Scripta(2020)·4 citations
5. 05*

   Diphoton production in vector-boson scattering at the LHC at next-to-leading order QCD

   Francisco Campanario🇪🇸 · Matthias Kerner🇨🇭 · Le Duc Ninh🇻🇳 · Ivan Rosario🇪🇸

   In this paper, we present results at next-to-leading order (NLO) QCD for photon pair production in association with two jets via vector boson scattering within the Standard Model (SM), and also in an effective field theory framework with anomalous gauge coupling effects via bosonic dimension-6 and 8 operators. We observe that, compared to other processes in the class of two electroweak (EW) vector boson production in association with two jets, more exclusive cuts are needed in order to suppress the SM QCD-induced background channel. As expected, the NLO QCD corrections reduce the scale uncertainties considerably. Using a well-motivated dynamical scale choice, we find moderate $K$-factors for the EW-induced process while the QCD-induced channel receives much larger corrections. Furthermore, we observe that applying a cut of $\Delta {\varphi }_{j_2{\gamma }_1}^{\text{cut}}<2.5$ for the second hardest jet and the hardest photon helps to increase the signal significance and reduces the impact of higher-order QCD corrections.

   hep-phJHEP(2020)·12 citations
6. 06*

   Constraining visible neutrino decay at KamLAND and JUNO

   Yago P. Porto-Silva🇧🇷 · Suprabh Prakash🇧🇷 · O. L. G. Peres🇧🇷 · Hiroshi Nunokawa🇧🇷 · Hisakazu Minakata🇺🇸

   We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO. Assuming the Majoron model of neutrino decay, we obtain constraints on the couplings between Majoron and neutrino as well as on the lifetime/mass of the most massive neutrino state i.e., ${\tau }_3/m_3$ or ${\tau }_2/m_2$, respectively, for the normal or the inverted mass orderings. We obtain the constraints on the lifetime ${\tau }_2/m_2\ge 1.4\times 10^{-9}s/eV$ in the inverted mass ordering for both KamLAND and JUNO at 90% CL. In the normal ordering in which the bound can be obtained for JUNO only, the constraint is milder than the inverted ordering case, ${\tau }_3/m_3\ge 1.0\times 10^{-10}s/eV$ at 90% CL. We find that the dependence of lightest neutrino mass ($=m_{\mathrm{lightest}}$), $m_1(m_3)$ for the normal (inverted) mass ordering, on the constraints for the different types of couplings (scalar or pseudo-scalar) is rather strong, but the $m_{\mathrm{lightest}}$ dependence on the lifetime/mass bound is only modest.

   hep-phhep-exEPJC(2020)·33 citations
7. 07*

   Radiative corrections to the lepton flavor mixing in dense matter

   Jing-yu Zhu🇨🇳

   One-loop radiative corrections will lead to a small difference between the matter potentials developed by ${\nu }_{\mu }^{}$ and ${\nu }_{\tau }$ when they travel in a medium. By including such radiative corrections, we derive the exact expressions of the corresponding effective mass-squared differences and the moduli square of the lepton flavor mixing matrix elements $|{\tilde{U}}_{\alpha i}^{}{|}^2$ (for $\alpha =e,\mu ,\tau$ and $i=1,2,3$) in matter in the standard three-flavor mixing scheme and focus on their asymptotic behaviors when the matter density is very big (i.e., the matter effect parameter $A\equiv 2\sqrt{2}{G}_{\mathrm{F}}^{}{N}_e^{}E$ is very big). Different from the non-trivial fixed value of $|{\tilde{U}}_{\alpha i}^{}{|}^2$ in the $A\to \infty$ limit in the case without radiative corrections, we get $|{\tilde{U}}_{\alpha i}^{}{|}^2=0\mathrm{or}1$ under this extreme condition. The radiative corrections can significantly affect the lepton flavor mixing in dense matter, which are numerically and analytically discussed in detail. Furthermore, we also extend the discussion to the $(3+1)$ active-sterile neutrino mixing scheme.

   hep-phJHEP(2020)·6 citations
8. 08*

   Stochastic Axion Dark Matter in Axion Landscape

   Shota Nakagawa🇯🇵 · Fuminobu Takahashi🇯🇵 · Wen Yin🇰🇷

   We study the stochastic axion dark matter scenario in the axion landscape, where one of the axions is light and stable and therefore explains dark matter. If the axion mass at the potential is a typical value of the curvature along the direction, the potential can be well approximated by a quadratic mass term. On the other hand, if the axion mass happens to be suppressed in the vicinity of the minimum, the potential may be approximated by a quartic potential plus a suppressed quadratic one, for which the initial angle, and thus the axion abundance, can be significantly suppressed compared to the quadratic case. We delineate the viable parameter region by taking account of various observational constraints, and find that a broader range of the inflation scale is allowed. Also, if the curvature of the potential is suppressed over a certain range of the potential, the onset of coherent oscillations can be delayed. Then, the axion dark matter with a small decay constant is possible. We also discuss the {\pi}nflation mechanism to realize the hilltop initial condition in the stochastic axion scenario.

   hep-phastro-ph.COhep-thJCAP(2020)·41 citations
9. 09*

   A multi-charged particle model with local $U(1{)}_{\mu -\tau }$ to explain muon $g-2$, flavor physics, and possible collider signature

   Nilanjana Kumar🇮🇳 · Takaaki Nomura🇰🇷 · Hiroshi Okada🇰🇷

   We consider a model with multi-charged particles including vector-like fermions and a charged scalar under a local $U(1{)}_{\mu -\tau }$ symmetry. We search for allowed parameter region explaining muon anomalous magnetic moment (muon $g-2$) and $b\to s{\ell }^{+}{\ell }^{-}$ anomalies, satisfying constraints from the lepton flavor violations, $Z$ boson decays, meson anti-meson mixing and collider experiments. Carrying out numerical analysis, we explore the typical size of the muon $g-2$ and Wilson coefficients to explain $b\to s{\ell }^{+}{\ell }^{-}$ anomalies in our model when all other experimental constraints are satisfied. We then discuss the collider physics of the multicharged vectorlike fermions, considering some benchmark points in the allowed parameter space.

   hep-phCPC(2022)·12 citations
10. 10*

    Les Houches 2019 Physics at TeV Colliders: New Physics Working Group Report

    G. Brooijmans🇺🇸 · A. Buckley🇬🇧 · S. Caron🇳🇱 · A. Falkowski🇫🇷 · B. Fuks🇫🇷 · A. Gilbert🇺🇸 · W. J. Murray🇬🇧 · M. Nardecchia🇮🇹 · J. M. No🇪🇸 · R. Torre🇨🇭 · T. You🇨🇭 · G. Zevi Della Porta🇨🇭 and 78 other authors

    This report presents the activities of the `New Physics' working group for the `Physics at TeV Colliders' workshop (Les Houches, France, 10--28 June, 2019). These activities include studies of direct searches for new physics, approaches to exploit published data to constrain new physics, as well as the development of tools to further facilitate these investigations. Benefits of machine learning for both the search for new physics and the interpretation of these searches are also presented.

    hep-phhep-ex96 citations
11. 11*

    On the systematic construction of basis invariants

    Andreas Trautner🇩🇪

    We describe a new, generally applicable strategy for the systematic construction of basis invariants (BIs). Our method allows one to count the number of mutually independent BIs and gives controlled access to the interrelations (syzygies) between mutually dependent BIs. Due to the novel use of orthogonal hermitian projection operators, we obtain the shortest possible invariants and their interrelations. The substructure of non-linear BIs is fully resolved in terms of linear, basis-covariant objects. The substructure distinguishes real (CP-even) and purely imaginary (CP-odd) BIs in a simple manner. As an illustrative example, we construct the full ring of BIs of the scalar potential of the general Two-Higgs-Doublet model.

    hep-phJ.Phys.Conf.Ser.(2020)·10 citations
12. 12*

    Road map to extracting medium properties: an overview

    Liliana Apolinário🇵🇹

    In this manuscript, it is presented an overview of the Quark-Gluon Plasma properties measured, so far, using hard probes. We will focus on both quantitative and qualitative properties that have been (or are about to be) measured, making a link between the theoretical description and experimental results. Throughout the manuscript, highlights to some of the conferences' results will be given, but without an extensive overview. A personal opinion of the most important developments and critical problems that need more work in the future is presented at the end.

    hep-phNPA(2021)·0 citations
13. 13*

    Time evolution of a medium-modified jet

    Liliana Apolinário🇵🇹

    The presence of a hot and dense medium, produced in ultra-relativistic heavy-ion collisions, is known to modify the parton shower evolution. Several observations of the resulting intra-jet activity show significant modifications of what can be considered as a medium-modified jet from a "vacuum" (proton-proton) reference. These modifications, generically known as jet quenching effects, are the result of the multiple interactions of the parton shower with the produced fast-evolving quark-gluon plasma (QGP). Recent efforts have tried to assess the time dependence of jet quenching effects, with particular focus on late or early dynamics. In this talk, we show a novel tool that can potentially evaluate the full-time evolution of the QGP by applying jet reclustering techniques. The result can bring novel insights into the QGP expansion as well as shed some light on how to re-sum, in a consistent way, vacuum-like and medium-like emissions into a single parton shower evolution equation.

    hep-phPoS(2020)·0 citations
14. 14*

    Electroweak Stability and Discovery Luminosities for New Physics

    Kerem Cankocak🇹🇷 · Durmus Demir🇹🇷 · Canan Karahan🇹🇷 · Sercan Sen🇹🇷

    What is the luminosity needed for discovering new physics if the electroweak scale is to remain stable? In this work we study this question, with the example of a real singlet scalar which couples to the Higgs field already at the renormalizable level. Observing that the electroweak scale remains stable if the two scalars couple in a seesawic fashion, we show that the HL-LHC, expected to deliver an integrated luminosity around 3/ab, can discover scalars weighing up to 800 GeV. The FCC-hh, on the other hand, can discover scalars as heavy as 2.3 TeV at 100/ab luminosity. It thus follows that the new physics that does not destabilize the electroweak scale can be accessed only at high luminosities, and is not possible exclude by the current LHC results.

    hep-phEPJC(2020)·9 citations
15. 15*

    Probing charged lepton number violation via ${\ell }^{\pm }{\ell }^{\prime \pm }{W}^{\mp }{W}^{\mp }$

    Mayumi Aoki🇯🇵 · Kazuki Enomoto🇯🇵 · Shinya Kanemura🇯🇵

    We study impacts of dimension-five lepton-number violating operators associated with two same-sign weak bosons, ${\ell }^{\pm }{\ell }^{\prime \pm }{W}^{\mp }{W}^{\mp }$, on current and future experiments for neutrino oscillation, lepton-number violating rare processes and high-energy collider experiments. These operators can contain important information on the origin of tiny neutrino masses, which is independent of that from the so-called Weinberg operator. We examine constraints on the coefficients of the operators by the neutrino oscillation data. Upper bounds on the coefficients are also investigated by using the data for processes of lepton number violation such as neutrinoless double beta decays and ${\mu }^{-}$-$e^{+}$ conversion. These operators can also be directly tested by searching for lepton-number violating dilepton production via the same-sign W boson fusion process at high-energy hadron colliders like the Large Hadron Collider. We find that these operators can be considerably probed by these current and future experiments.

    hep-phPRD(2020)·14 citations
16. 16*

    Reinterpreting Neutrino Oscillations

    M. Bergevin🇺🇸

    This letter proposes an alternative quantum mechanical picture for the observed phenomena of neutrino oscillations. It is assumed in the following that neutrinos interact via diabatic (or localised) interactions with a new particle field, which changes their flavor. Furthermore, it is assumed that each neutrino flavor state can only have a single associated mass thereby making them fundamental particles of nature. The effective masses associated with matter interactions replace the concept of neutrino mixing angles. Preliminary evidence that left-handed neutrinos and right-handed antineutrinos oscillate differently is presented, implying charge-parity violation. Given the apparent anomalous observations of some neutrino oscillation experiments, which have led to speculations about the existence of a fourth (sterile) neutrino, it is worth examining the oscillation behavior predicted by alternative mechanisms to determine if they more naturally explain the available data.

    hep-ph0 citations
17. 17*

    Jet tagging made easy

    J. A. Aguilar-Saavedra🇪🇸 · B. Zaldivar🇪🇸

    We develop taggers for multi-pronged jets that are simple functions of jet substructure (so-called `subjettiness') variables. These taggers can be approximately decorrelated from the jet mass in a quite simple way. Specifically, we use a Logistic Regression Design (LoRD) which, even being one of the simplest machine learning classifiers, shows a performance which surpasses that of simple variables used by the ATLAS and CMS Collaborations and is not far from more complex models based on neural networks. Contrary to the latter, our method allows for an easy implementation of tagging tasks by providing a simple and interpretable analytical formula with already optimised parameters.

    hep-phEPJC(2020)·12 citations
18. 18*

    Non-standard neutrino interactions in $U(1{)}^{\prime }$ model after COHERENT data

    L. J. Flores🇲🇽 · Newton Nath🇲🇽 · E. Peinado🇲🇽

    We explore the potential to prove light extra gauge $Z^{\prime }$ boson inducing non-standard neutrino interactions (NSIs) in the coherent-elastic neutrino-nucleus scattering (CE$\nu$NS) experiments. We intend to examine how the latest COHERENT-CsI and CENNS-10 data can constrain this model. A detailed investigation for the upcoming Ge, LAr-1t, and NaI detectors of COHERENT collaboration has also been made. Depending on numerous other constraints coming from oscillation experiments, muon $(g-2)$, beam-dump experiments, LHCb, and reactor experiment CONUS, we explore the parameter space in $Z^{\prime }$ boson mass vs coupling constant plane. Moreover, we study the predictions of two-zero textures that are allowed in the concerned model in light of the latest global-fit data.

    hep-phJHEP(2020)·66 citations
19. 19*

    Tag N' Train: A Technique to Train Improved Classifiers on Unlabeled Data

    Oz Amram🇺🇸 · Cristina Mantilla Suarez🇺🇸

    There has been substantial progress in applying machine learning techniques to classification problems in collider and jet physics. But as these techniques grow in sophistication, they are becoming more sensitive to subtle features of jets that may not be well modeled in simulation. Therefore, relying on simulations for training will lead to sub-optimal performance in data, but the lack of true class labels makes it difficult to train on real data. To address this challenge we introduce a new approach, called Tag N' Train (TNT), that can be applied to unlabeled data that has two distinct sub-objects. The technique uses a weak classifier for one of the objects to tag signal-rich and background-rich samples. These samples are then used to train a stronger classifier for the other object. We demonstrate the power of this method by applying it to a dijet resonance search. By starting with autoencoders trained directly on data as the weak classifiers, we use TNT to train substantially improved classifiers. We show that Tag N' Train can be a powerful tool in model-agnostic searches and discuss other potential applications.

    hep-phhep-exJHEP(2021)·98 citations
20. 20*

    Local spin polarizations in relativistic heavy ion collisions

    Shuai Y. F. Liu🇺🇸 · Yifeng Sun🇮🇹 · Che Ming Ko🇺🇸

    Based on a generalized side-jump formalism for massless chiral fermions, which naturally takes into account the spin-orbit coupling in the scattering of two chiral fermions and the chiral vortical effect in a rotating chiral fermion matter, we have developed a covariant and total angular momentum conserved chiral transport model to study both the global and local polarizations of this matter. For a system of massless quarks of random spin orientations and finite vorticity in a box, we have demonstrated that the model can exactly conserve the total angular momentum of the system and dynamically generate the quark spin polarization expected from a thermally equilibrated quark matter. Using this model to study the spin polarization in relativistic heavy-ion collision, we have found that the local quark spin polarizations depend strongly on the reference frame where they are evaluated as a result of the nontrivial axial charge distribution caused by the chiral vortical effect. We have further shown that because of the anomalous orbital or side-jump contribution to the quark spin polarization, the local quark polarizations calculated in the medium rest frame are qualitatively consistent with the local polarizations of Lambda hyperons measured in experiments.

    ↳ nucl-thhep-phnucl-exNPA(2021)·3 citations
21. 21*

    Quark and lepton mass matrices from localization in M-theory on $G_2$ orbifold

    Eric Gonzalez🇺🇸 · Gordon Kane🇺🇸 · Khoa Dang Nguyen🇺🇸 · Malcolm J. Perry🇬🇧

    M-theory compactified on a $G_2$ manifold with resolved $E_8$ singularities realizes 4d $\mathcal{N}=1$ supersymmetric gauge theories coupled to gravity with three families of Standard Model fermions. Beginning with one $E_8$ singularity, three fermion families emerge when $E_8$ is broken by geometric engineering deformations to a smaller subgroup with equal rank. In this paper, we use the local geometry of the theory to explain the origin of the three families and their mass hierarchy. We linearize the blowing-up of 2-cycles associated with resolving $E_8$ singularities. After imposing explicit constraints on the effectively stabilized moduli, we arrive at Yukawa couplings for the quarks and leptons. We fit the high scale Yukawa couplings approximately which results in the quark masses agreeing reasonably well with the observations, implying that the experimental hierarchy of the masses is achievable within this framework. The hierarchy separation of the top quark from the charm and up is a stringy effect, while the spitting of the charm and up also depends on the Higgs sector. The Higgs sector cannot be reduced to having a single vev; all three vevs must be non-zero.Three extra $U(1)$'s survive to the low scale but are not massless, so Z' states are motivated to occur in the spectrum, but may be massive.

    ↳ hep-thhep-phPRD(2021)·2 citations
22. 22*

    Long-range collectivity in small collision-systems with two- and four-particle correlations @ STAR

    Roy A. Lacey (for the STAR Collaboration)🇺🇸

    New STAR differential and integral v{2,3} measurements that explicitly account for non-flow contributions are reported for p/d/3He+Au, collisions at Roots=200 GeV. The measurements, which leverage the two-particle correlators for p/d/3He+Au and minimum-bias p+p collisions in tandem with three well-established methods of non-flow subtraction, are observed to be method-independent. For comparable multiplicities, they further indicate system-independent v2{2} and v3{2} values that are consistent with the critical role of both size (N{ch}) and the subnucleonic-fluctuations-driven eccentricities e{2,3} but are inconsistent with the notion of shape engineering in p/d/3He+Au collisions. The scaling function derived from the measurements, confirm the important role of final-state effects across a broad spectrum of collision-system sizes and energies and suggests an increase in eta/s(T,muB) for small collision-systems.

    ↳ nucl-exhep-exhep-phnucl-thNPA(2021)·14 citations
23. 23*

    Structure Formation Models Weaken Limits on WIMP Dark Matter from Dwarf Spheroidal Galaxies

    Shin'ichiro Ando🇳🇱 · Alex Geringer-Sameth🇬🇧 · Nagisa Hiroshima🇯🇵 · Sebastian Hoof🇩🇪 · Roberto Trotta🇬🇧 · Matthew G. Walker🇺🇸

    Dwarf spheroidal galaxies that form in halo substructures provide stringent constraints on dark matter annihilation. Many ultrafaint dwarfs discovered with modern surveys contribute significantly to these constraints. At present, because of the lack of abundant stellar kinematic data for the ultrafaints, non-informative prior assumptions are usually made for the parameters of the density profiles. Based on semi-analytic models of dark matter subhalos and their connection to satellite galaxies, we present more informative and realistic satellite priors. We show that our satellite priors lead to constraints on the annihilation rate that are between a factor of 2 and a factor of 7 weaker than under non-informative priors. As a result, the thermal relic cross section can at best only be excluded (with 95% probability) for dark matter masses of $\lesssim 40$ GeV from dwarf spheroidal data, assuming annihilation into $b\bar{b}$.

    ↳ astro-ph.COastro-ph.HEhep-phPRD(2020)·70 citations
24. 24*

    New developments in lattice QCD on equilibrium physics and phase diagram

    Heng-Tong Ding🇨🇳

    I review recent new lattice QCD results on a few selected topics which are relevant to the heavy ion physics community. Special emphasis is put on the QCD phase diagram towards the chiral limit and at nonzero baryon density as well as the fate of quarkonia and heavy quark drag coefficients.

    ↳ hep-lathep-phnucl-exnucl-thNPA(2021)·38 citations
25. 25*

    Parton distribution functions of ${\Delta }^{+}$ on the lattice

    Yahui Chai🇨🇳 · Yuan Li🇨🇳 · Shicheng Xia🇨🇳 · Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Xu Feng🇨🇳 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Giannis Koutsou🇨🇾 · Chuan Liu🇨🇳 · Aurora Scapellato🇵🇱 · Fernanda Steffens🇩🇪

    We perform a first calculation for the unpolarized parton distribution function of the ${\Delta }^{+}$ baryon using lattice QCD simulations within the framework of Large Momentum Effective Theory. Two ensembles of $N_f=2+1+1$ twisted mass fermions are utilized with a pion mass of 270 MeV and 360 MeV, respectively. The baryon, which is treated as a stable single-particle state, is boosted with momentum $P_3$ with values $\{0.42,0.83,1.25\}$ GeV, and we utilize momentum smearing to improve the signal. The unpolarized parton distribution function of ${\Delta }^{+}$ is obtained using a non-perturbative renormalization and a one-loop formula for the matching, with encouraging precision. In particular, we compute the $\overline{d}(x)-\overline{u}(x)$ asymmetry and compare it with the same quantity in the nucleon, in a first attempt towards resolving the physical mechanism responsible for generating such asymmetry.

    ↳ hep-lathep-phPRD(2020)·71 citations
26. 26*

    Probing the dark sector via searches for invisible decays of the Higgs boson at the ILC

    Yu Kato🇯🇵

    Although the existence of Dark Matter (DM) has been suggested by various astrophysical observations, it has not yet been discovered today. We can assume a scenario in which the particles that account for the DM can interact with the Standard Model particles only through their couplings with the Higgs sector, the so-called Higgs-portal model. This model can be investigated by collider experiment using the invisible decay of Higgs boson. In this study, we evaluate the search ability of International Linear Collider (ILC) for invisible decay of the Higgs using International Large Detector (ILD) full detector simulation. We estimate 95% C.L. upper limit (UL) on the branching ratio of invisible Higgs decays and compare them between two center-of-mass energy conditions: $\sqrt{s}=250$ GeV and 500 GeV. In addition, we describe the complementarity of lepton collider experiment to the direct detection experiment about DM search ability.

    ↳ hep-exhep-phPoS(2020)·14 citations
27. 27*

    Charm CPV: observation and prospects

    Miroslav Saur (University of Chinese Academy of Sciences)🇨🇳 · Fu-Sheng Yu (Lanzhou university)🇨🇳

    An overview of the recent first observation of CP violation in the Charm sector by the LHCb collaboration. Selection of theoretical models explaining this measurement is reviewed. Finally, experimental prospects for future measurements are discussed.

    ↳ hep-exhep-phSci.Bull.(2020)·38 citations
28. 28*

    Hydrodynamic response to jets with a source based on causal diffusion

    Y. Tachibana🇺🇸 · A. Angerami🇺🇸 · S. A. Bass🇺🇸 · S. Cao🇺🇸 · Y. Chen🇨🇳 · J. Coleman🇺🇸 · L. Cunqueiro🇺🇸 · T. Dai🇺🇸 · L. Du🇺🇸 · R. Ehlers🇺🇸 · H. Elfner🇩🇪 · D. Everett🇺🇸 and 38 other authors

    We study the medium response to jet evolution in the quark-gluon plasma within the JETSCAPE framework. Recoil partons' medium response in the weakly coupled description is implemented in the multi-stage jet energy-loss model in the framework. As a further extension, the hydrodynamic description is rearranged to include in-medium jet transport based on a strong-coupling picture. To interface hydrodynamics with jet energy-loss models, the hydrodynamic source term is modeled by a causal formulation employing the relativistic diffusion equation. The jet shape and fragmentation function are studied via realistic simulations with weakly coupled recoils. We also demonstrate modifications in the medium caused by the hydrodynamic response.

    ↳ nucl-thhep-phnucl-exNPA(2021)·21 citations
29. 29*

    Effective Field Theory in AdS: Continuum Regime, Soft Bombs, and IR Emergence

    Alexandria Costantino🇺🇸 · Sylvain Fichet🇧🇷 · Philip Tanedo🇺🇸

    We consider a scalar field in a slice of Lorentzian five-dimensional AdS at arbitrary energies. We show that the presence of bulk interactions separate the behavior of the theory into two different regimes: Kaluza--Klein and continuum. We determine the transition scale between these regimes and show that UV brane correlation functions are independent of IR brane-localized operators for four-momenta beyond this transition scale. The same bulk interactions that induce the transition also give rise to cascade decays. We study these cascade decays for the case of a cubic self-interaction in the continuum regime. We find that the cascade decay progresses slowly towards the IR region and gives rise to soft spherical final states, in accordance with former results from both gravity and CFT. We identify a recursion relation between integrated squared amplitudes of different leg numbers and thus evaluate the total rate. We find that cascade decays in the continuum regime are exponentially suppressed. This feature completes the picture of the IR brane as an emergent sector as seen from the UV brane. We briefly discuss consistency with the holographic dual description of glueballs and some implications for dark sector models.

    ↳ hep-thhep-phPRD(2020)·26 citations
30. 30*

    Leading hadronic contribution to the muon magnetic moment from lattice QCD

    Sz. Borsanyi🇩🇪 · Z. Fodor🇩🇪 · J. N. Guenther🇩🇪 · C. Hoelbling🇩🇪 · S. D. Katz🇭🇺 · L. Lellouch🇫🇷 · T. Lippert🇩🇪 · K. Miura🇩🇪 · L. Parato🇫🇷 · K. K. Szabo🇩🇪 · F. Stokes🇩🇪 · B. C. Toth🇩🇪 · Cs. Torok🇩🇪 · L. Varnhorst🇩🇪

    We compute the leading order hadronic vacuum polarization (LO-HVP) contribution to the anomalous magnetic moment of the muon, $(g_{\mu }-2)$, using lattice QCD. Calculations are performed with four flavors of 4-stout-improved staggered quarks, at physical quark masses and at six values of the lattice spacing down to 0.064~fm. All strong isospin breaking and electromagnetic effects are accounted for to leading order. The infinite-volume limit is taken thanks to simulations performed in volumes of sizes up to 11~fm. Our result for the LO-HVP contribution to $(g_{\mu }-2)$ has a total uncertainty of 0.8\%. Compared to the result of the dispersive approach for this contribution, ours significantly reduces the tension between the standard model prediction for $(g_{\mu }-2)$ and its measurement.

    ↳ hep-lathep-phNature(2021)·1250 citations
31. 31*

    Neutral baryonic systems with strangeness

    H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸

    We review the status as regards the existence of three- and four-body bound states made of neutrons and $\Lambda$ hyperons. For interesting cases, the coupling to neutral baryonic systems made of charged particles of different strangeness has been addressed. There are strong arguments showing that the $\Lambda nn$ system has no bound states. $\Lambda \Lambda nn$ strong stable states are not favored by our current knowledge of the strangeness $-1$ and $-2$ baryon-baryon interactions. However, a possible ${\Xi }^{-}t$ quasibound state decaying to $\Lambda \Lambda nn$ might exist in nature. Similarly, there is a broad agreement about the nonexistence of $\Lambda \Lambda n$ bound states. However, the coupling to $\Xi NN$ states opens the door to a resonance above the $\Lambda \Lambda n$ threshold.

    ↳ nucl-thhep-phIJMPE(2020)·1 citation
32. 32*

    Spurious Point Source Signals in the Galactic Center Excess

    Rebecca K. Leane🇺🇸 · Tracy R. Slatyer🇺🇸

    We re-examine evidence that the Galactic Center Excess (GCE) originates primarily from point sources (PSs). We show that in our region of interest, non-Poissonian template fitting (NPTF) evidence for GCE PSs is an artifact of unmodeled north-south asymmetry of the GCE. This asymmetry is strongly favored by the fit (although it is unclear if this is physical), and when it is allowed, the preference for PSs becomes insignificant. We reproduce this behavior in simulations, including detailed properties of the spurious PS population. We conclude that NTPF evidence for GCE PSs is highly susceptible to certain systematic errors, and should not at present be taken to robustly disfavor a dominantly smooth GCE.

    ↳ astro-ph.HEastro-ph.COhep-phPRL(2020)·74 citations
33. 33*

    The Enigmatic Galactic Center Excess: Spurious Point Sources and Signal Mismodeling

    Rebecca K. Leane🇺🇸 · Tracy R. Slatyer🇺🇸

    The Galactic Center GeV excess (GCE) has garnered great interest as a possible signal of either dark matter annihilation or some novel astrophysical phenomenon, such as a new population of gamma-ray emitting pulsars. In a companion paper, we showed that in a $10^{\circ }$ radius region of interest (ROI) surrounding the Galactic Center, apparent evidence for GCE point sources (PSs) from non-Poissonian template fitting (NPTF) is actually an artifact of unmodeled north-south asymmetry of the GCE. In this work, we develop a simplified analytic description of how signal mismodeling can drive an apparent preference for a PS population, and demonstrate how the behavior pointed out in the companion paper also appears in simpler simulated datasets that contain no PS signals at all. We explore the generality of this behavior in the real gamma-ray data, and discuss the implications for past and future studies using NPTF techniques. While the drop in PS preference once north-south asymmetry is included is not ubiquitous in larger ROIs, we show that any overly-rigid signal model is expected to yield a spurious PS signal that can appear very convincing: as well as apparent significance comparable to what one would expect from a true PS population, the signal can exhibit stability against a range of variations in the analysis, and a source count function that is very consistent with previous apparent NPTF-based detections of a GCE PS population. This contrasts with previously-studied forms of systematic mismodeling which are unlikely to mimic a PS population in the same way. In the light of this observation, and its explicit realization in the region where the GCE is brightest, we argue that a dominantly smooth origin for the GCE is not in tension with existing NPTF analyses.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2020)·67 citations
34. 34*

    Foreground Mismodeling and the Point Source Explanation of the Fermi Galactic Center Excess

    Malte Buschmann🇺🇸 · Nicholas L. Rodd🇺🇸 · Benjamin R. Safdi🇺🇸 · Laura J. Chang🇺🇸 · Siddharth Mishra-Sharma🇺🇸 · Mariangela Lisanti🇺🇸 · Oscar Macias🇯🇵

    The Fermi Large Area Telescope has observed an excess of ~GeV energy gamma rays from the center of the Milky Way, which may arise from near-thermal dark matter annihilation. Firmly establishing the dark matter origin for this excess is however complicated by challenges in modeling diffuse cosmic-ray foregrounds as well as unresolved astrophysical sources, such as millisecond pulsars. Non-Poissonian Template Fitting (NPTF) is one statistical technique that has previously been used to show that at least some fraction of the GeV excess is likely due to a population of dim point sources. These results were recently called into question by Leane and Slatyer (2019), who showed that a synthetic dark matter annihilation signal injected on top of the real Fermi data is not recovered by the NPTF procedure. In this work, we perform a dedicated study of the Fermi data and explicitly show that the central result of Leane and Slatyer (2019) is likely driven by the fact that their choice of model for the Galactic foreground emission does not provide a sufficiently good description of the data. We repeat the NPTF analyses using a state-of-the-art model for diffuse gamma-ray emission in the Milky Way and introduce a novel statistical procedure, based on spherical-harmonic marginalization, to provide an improved description of the Galactic diffuse emission in a data-driven fashion. With these improvements, we find that the NPTF results continue to robustly favor the interpretation that the Galactic Center excess is due, in part, to unresolved astrophysical point sources across the analysis variations that we have explored.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2020)·99 citations
35. 35*

    The Two-Loop Four-Graviton Scattering Amplitudes

    S. Abreu🇧🇪 · F. Febres Cordero🇺🇸 · H. Ita🇩🇪 · M. Jaquier🇩🇪 · B. Page🇫🇷 · M. S. Ruf🇩🇪 · V. Sotnikov🇩🇪

    We present the analytic form of the two-loop four-graviton scattering amplitudes in Einstein gravity. To remove ultraviolet divergences we include counterterms quadratic and cubic in the Riemann curvature tensor. The two-loop numerical unitarity approach is used to deal with the challenging momentum dependence of the interactions. We exploit the algebraic properties of the integrand of the amplitude in order to map it to a minimal basis of Feynman integrals. Analytic expressions are obtained from numerical evaluations of the amplitude. Finally, we show that four-graviton scattering observables depend on fewer couplings than naively expected.

    ↳ hep-thgr-qchep-phPRL(2020)·46 citations
36. 36*

    Constraints on Primordial Black Holes

    Bernard Carr🇬🇧 · Kazunori Kohri🇯🇵 · Yuuiti Sendouda🇯🇵 · Jun'ichi Yokoyama🇯🇵

    We update the constraints on the fraction of the Universe that may have gone into primordial black holes (PBHs) over the mass range $10^{-5}\text{–}10^{50}$ g. Those smaller than $\sim 10^{15}$ g would have evaporated by now due to Hawking radiation, so their abundance at formation is constrained by the effects of evaporated particles on big bang nucleosynthesis, the cosmic microwave background (CMB), the Galactic and extragalactic $\gamma$-ray and cosmic ray backgrounds and the possible generation of stable Planck mass relics. PBHs larger than $\sim 10^{15}$ g are subject to a variety of constraints associated with gravitational lensing, dynamical effects, influence on large-scale structure, accretion and gravitational waves. We discuss the constraints on both the initial collapse fraction and the current fraction of the CDM in PBHs at each mass scale but stress that many of the constraints are associated with observational or theoretical uncertainties. We also consider indirect constraints associated with the amplitude of the primordial density fluctuations, such as second-order tensor perturbations and $\mu$-distortions arising from the effect of acoustic reheating on the CMB, if PBHs are created from the high-$\sigma$ peaks of nearly Gaussian fluctuations. Finally we discuss how the constraints are modified if the PBHs have an extended mass function, this being relevant if PBHs provide some combination of the dark matter, the LIGO/Virgo coalescences and the seeds for cosmic structure. Even if PBHs make a small contribution to the dark matter, they could play an important cosmological role and provide a unique probe of the early Universe.

    ↳ astro-ph.COgr-qchep-phhep-thRept.Prog.Phys.(2021)·1603 citations
37. 37*

    Test of Kerr-Sen metric with black hole observations

    Ashish Narang🇮🇳 · Subhendra Mohanty🇮🇳 · Abhass Kumar🇮🇳

    The Kerr-Sen black hole is a rotating charged black hole solution arising from heterotic string theory. In 4-dimensions effective theory the bosonic fields are: a $U(1)$ gauge boson, a Kalb-Ramond 3-form which is equivalent to a pseudoscalar axion in 4-dimensions, the dilaton and the graviton. The coupling constants in the theory are ${\alpha }^{\prime }$ (inverse string tension) and $\kappa$ (inverse reduced Planck mass in 4-dimensions) and the charge of the $U(1)$ field and the axion-photon coupling are related to these two. Sen found a black hole solution (the Kerr-Sen black hole) with these fields as the external hair of the black hole. In this paper we investigate the possibility of determining the Sen solution from observations. The observations which can test the Kerr-Sen black hole are: (a) determination of the shape of the photon shadow, and (b) the rotation of polarization of photon due to axion hair. The deviation from circularity gives the $U(1)$ charge of the black hole and identification of this charge in terms of the photon coupling leads to a prediction of frequency independent "Faraday rotation" in terms of black hole parameters already determined from the shadow. Similar measurements of Kerr-Newman black hole with axion hair have no correlation between the shape of the image and the amount of "Faraday rotation". This correlation can be a distinctive test of the Sen metric. In the recent observation from EHT of M87* shadow, the deviation from circularity has an upper bound of 10%. If this observation is refined to 1% accuracy then a definitive prediction of the charge of the Kerr-Sen black hole and the "Faraday rotation" can be made. Interestingly observations of "Faraday rotation" have shown that the effect is independent of frequency pointing to an axionic hair interpretation for the effect.

    ↳ gr-qchep-ph34 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.