Wed·Mar 27, 2019Wednesday·March 27, 2019

1. 01*

   Neutrino mass models: New classification and model-independent upper limits on their scale

   Juan Herrero-Garcia🇮🇹 · Michael A. Schmidt🇦🇺

   We propose a model-independent framework to classify and study neutrino mass models and their phenomenology. The idea is to introduce one particle beyond the Standard Model which couples to leptons and carries lepton number together with an operator which violates lepton number by two units and contains this particle. This allows to study processes which do not violate lepton number, while still working with an effective field theory. The contribution to neutrino masses translates to a robust upper bound on the mass of the new particle. We compare it to the stronger but less robust upper bound from Higgs naturalness and discuss several lower bounds. Our framework allows to classify neutrino mass models in \emph{just} 20 categories, further reduced to 14 once nucleon decay limits are taken into account, and \emph{possibly} to 9 if also Higgs naturalness considerations and direct searches are considered.

   hep-phEPJC(2019)·27 citations
2. 02*

   Towards a complete angular analysis of the electroweak penguin decay ${\Lambda }_b^0\to p{h}^{-}{\ell }^{+}{\ell }^{-}$

   Biplab Dey🇨🇳

   We investigate the rare electroweak penguin transition $b\to s{\ell }^{+}{\ell }^{-}$ though angular analyses in baryonic $b$-decays. Instead of performing likelihood fits, that might suffer from ambiguity issues, we employ the moments technique, which is a simple counting experiment. The method is known to be robust under low statistics conditions and avoids the ambiguity problem by construction. We provide the full set of 32 orthonormal moments for ${\Lambda }_b^0\to p{h}^{-}{\ell }^{+}{\ell }^{-}$, where $h\in \{\pi ,K\}$, for a polarized ${\Lambda }_b^0$ and the dihadron system $[ph]$ being in a spin-1/2 state.

   hep-ph1 citation
3. 03*

   Correlation of heavy and light flavours in simulations

   Eszter Frajna🇭🇺 · Robert Vertesi🇭🇺

   The ALICE experiment at the Large Hadron Collider (LHC) ring is designed to study the strongly interacting matter at extreme energy densities created in high-energy heavy-ion collisions. In this paper we investigate correlations of heavy and light flavours in simulations at LHC energies at mid-rapidity, with the primary purpose of proposing experimental application of these methods. Our studies have shown that investigating the correlation images can aid the experimental separation of heavy quarks and help understanding the physics that create them. The shape of the correlation peaks can be used to separate the electrons stemming from b quarks. This could be a method of identification that, combined with identification in silicon vertex detectors, may provide much better sample purity for examining the secondary vertex shift. Based on a correlation picture it is also possible to distinguish between prompt and late contributions to D meson yields.

   hep-phUniverse(2019)·1 citation
4. 04*

   Dark Matter Through the Quark Vector Current Portal

   Dillon Berger🇺🇸 · Arvind Rajaraman🇺🇸 · Jason Kumar🇺🇸

   We consider models of light dark matter coupled to quarks through a vector current interaction. For low energies, these models must be treated through the effective couplings to mesons, which are implemented here through the chiral Lagrangian. We find the rates of dark matter annihilation and decay to the light mesons, and find the expected photon spectrum from the decay of the hadrons. We compare to current and future observations, and show that there is a significant discovery reach for these models.

   hep-phastro-ph.HEPramana(2020)·6 citations
5. 05*

   Implications on the first observation of charm CPV at LHCb

   Hsiang-nan Li🇹🇼 · Cai-Dian Lü🇨🇳 · Fu-Sheng Yu🇨🇳

   Very recently, the LHCb Collaboration observed the $CP$ violation (CPV) in the charm sector for the first time, with $\Delta A_{CP}^{\mathrm{dir}}\equiv A_{CP}(D^0\to K^{+}{K}^{-})-A_{CP}(D^0\to {\pi }^{+}{\pi }^{-})=(-1.54\pm 0.29)\times 10^{-3}$. This result is consistent with our prediction of $\Delta A_{CP}^{\mathrm{SM}}=(-0.57\sim -1.87)\times 10^{-3}$ obtained in the factorization-assisted topological-amplitude (FAT) approach in [PRD86,036012(2012)]. It implies that the current understanding of the penguin dynamics in charm decays in the Standard Model is reasonable. Motivated by the success of the FAT approach, we further suggest to measure the $D^{+}\to K^{+}{K}^{-}{\pi }^{+}$ decay, which is the next potential mode to reveal the CPV of the same order as $10^{-3}$.

   hep-phhep-ex66 citations
6. 06*

   Searching for Beyond the Standard Model Physics with COHERENT Energy and Timing Data

   Bhaskar Dutta🇺🇸 · Shu Liao🇺🇸 · Samiran Sinha🇺🇸 · Louis E. Strigari🇺🇸

   We search for beyond the Standard Model (BSM) physics by combining COHERENT energy and timing data. Focusing on light, $\lesssim$ GeV mediators, we find the data favor a $\sim 10-1000$ MeV mediator as compared to the Standard Model (SM) best fit at the $\lesssim 2\sigma$ level. The best-fit coupling range is $g\sim 10^{-5}-10^{-3}$. The timing data provides statistical information on the neutrino flavor distributions that is not attainable from the nuclear recoil energies alone. This result accounts for uncertainty in the effective size of the neutron distribution, and highlights the power of including uncertainties on experimental backgrounds, nuclear structure, and BSM physics.

   hep-phPRL(2019)·72 citations
7. 07*

   Impact of the chromo-electromagnetic field fluctuations on transport coefficients of heavy quarks and shear viscosity to entropy density ratio of quark-gluon plasma

   Ashik Ikbal Sheikh🇮🇳 · Zubayer Ahammed🇮🇳

   The chromo-electromagnetic field fluctuations in the quark-gluon plasma (QGP) play an important role as these field fluctuations result energy gain of heavy quarks. We consider these fluctuations and evaluate the transport coefficients, e.g., drag and diffusion coefficients of charm quarks and shear viscosity to entropy density ratio ($\eta /s$) of the QGP. We find a significant effect of such fluctuations on the transport coefficients. These fluctuations cause a reduction of the drag and diffusion coefficients. We also observe that the shear viscosity to entropy density ratio of the QGP is closer to the value obtained in Lattice QCD (LQCD) and functional renormalization group calculations when the effects of such fluctuations are included.

   hep-phnucl-thNPA(2019)·2 citations
8. 08*

   Structure Functions of the Nucleon in a Soliton Model

   I. Takyi🇿🇦 · H. Weigel🇿🇦

   We study nucleon structure functions in the soliton picture of the bosonized Nambu-Jona-Lasinio model. We focus on their vacuum contributions and examine whether they are outweighed by their valence quark counterparts.

   hep-phnucl-thJPS Conf.Proc.(2019)·1 citation
9. 09*

   Moments of multiplicity distributions using Tsallis statistics in leptonic and hadronic collisions

   S.Sharma🇮🇳 · M.Kaur🇮🇳

   Moments play a crucial role in investigating the characteristics of charged particle multiplicities in high energy interactions. The success of any model which describes the multiplicity data can be understood well by studying the normalised and factorial moments of that distribution.~The Tsallis model is one of the most successful models which describes the multiplicity spectra, transverse momentum ($p_T$) spectra very precisely in high energy interactions.~In our previous work we have used the Tsallis $q$-statistics to describe the multiplicity distributions in leptonic and hadronic collisions at various energies ranging from 14 GeV to 7 TeV.~In the present study we have extended our analysis for calculating the moments using the Tsallis model for $e^{+}{e}^{-}$ interactions at $\sqrt{s}$ = 91 to 206 GeV from the LEP data and for $pp$ interactions at $\sqrt{s}$ = 0.9 to 7 TeV in various pseudo-rapidity intervals from the CMS data at LHC. By using the Tsallis model we have also calculated the average charged multiplicity and its dependence on energy.~It is found that the moments and the mean multiplicities predicted by the Tsallis model are in good agreement with the experimental values.~We have also predicted the mean multiplicity at $\sqrt{s}$ = 500 GeV for $e^{+}{e}^{-}$ collisions and at $\sqrt{s}$ = 14 TeV for $pp$ collisions in extreme pseudo-rapidity interval, $|\eta |$ $<$ 2.4

   hep-phPRD(2019)·4 citations
10. 10*

    Simultaneous explanation of $K$ and $B$ anomalies in vectorlike compositeness

    Shinya Matsuzaki🇨🇳 · Kenji Nishiwaki🇰🇷 · Kei Yamamoto🇨🇭

    We address the presently reported significant flavor anomalies in the $K$ and $B$ meson systems such as the CP violating Kaon decay (${ϵ}^{\prime }/ϵ$) and lepton-flavor universality violation in $B$ meson decays ($R_{K^{(\ast )}},$ and also commenting $R_{D^{(\ast )}}$), by proposing flavorful and chiral vector bosons as the new physics constitution at $\sim 1\mathrm{TeV}$. Interestingly, if the new (composite) vector bosons are quite heavier than $\sim 1\mathrm{TeV}$, we face a difficulty in addressing the anomaly in ${ϵ}^{\prime }/ϵ$ consistently with the constraint from the $K^0$-$\overline{K^0}$ mixing. Both of the anomalies can be addressed within $1\sigma$ confidence levels individually, where the relevant parameter space will be investigated by the NA62 and KOTO experiments, in addition to direct searches at the large hadron collider.

    hep-phhep-exPoS(2019)·7 citations
11. 11*

    Single pseudoscalar meson pole and pion box contributions to the anomalous magnetic moment of the muon

    Gernot Eichmann🇵🇹 · Christian S. Fischer🇩🇪 · Esther Weil🇩🇪 · Richard Williams🇩🇪

    We present results for single pseudoscalar meson pole contributions and pion box contributions to the hadronic light-by-light (LBL) correction of the muon's anomalous magnetic moment. We follow the recently developed dispersive approach to LBL, where these contributions are evaluated with intermediate mesons on-shell. However, the space-like electromagnetic and transition form factors are not determined from analytic continuation of time-like data, but directly calculated within the functional approach to QCD using Dyson-Schwinger and Bethe-Salpeter equations. This strategy allows for a systematic comparison with a strictly dispersive treatment and also with recent results from lattice QCD. Within error bars, we obtain excellent agreement for the pion electromagnetic and transition form factor and the resulting contributions to LBL. In addition, we present results for the $\eta$ and ${\eta }^{\prime }$ pole contributions and discuss the dynamical effects in the $\eta -{\eta }^{\prime }$ mixing due to the strange quarks. Our result for the total pseudoscalar pole contributions is $a_{\mu }^{\text{PS-pole}}=91.6(1.9)\times 10^{-11}$ and for the pion-box contribution we obtain $a_{\mu }^{\pi -\text{box}}=-16.3(2)(4)\times 10^{-11}$.

    hep-phhep-latPLB(2019)·90 citations
12. 12*

    Implications for New Physics in $b\to s\mu \mu$ transitions after recent measurements by Belle and LHCb

    Kamila Kowalska🇵🇱 · Dinesh Kumar🇵🇱 · Enrico Maria Sessolo🇵🇱

    We present a Bayesian analysis of the implications for new physics in semileptonic $b\to s$ transitions after including new measurements of $R_K$ at LHCb and new determinations of $R_{K^{\ast }}$ and $R_{K^{\ast +}}$ at Belle. We perform global fits with 1, 2, 4, and 8 input Wilson coefficients, plus one CKM nuisance parameter to take into account uncertainties that are not factorizable. We infer the 68% and 95.4% credibility regions of the marginalized posterior probability density for all scenarios and perform comparisons of models in pairs by calculating the Bayes factor given a common data set. We then proceed to analyzing a few well known BSM models that can provide a high energy framework for the EFT analysis. These include the exchange of a heavy $Z^{{}^{\prime }}$ boson in models with heavy vector-like fermions and a scalar field, and a model with scalar leptoquarks. We provide predictions for the BSM couplings and expected mass values.

    hep-phEPJC(2019)·123 citations
13. 13*

    The Emergence of the $\Delta U=0$ Rule in Charm Physics

    Yuval Grossman🇺🇸 · Stefan Schacht🇺🇸

    We discuss the implications of the recent discovery of CP violation in two-body SCS $D$ decays by LHCb. We show that the result can be explained within the SM without the need for any large $SU(3)$ breaking effects. It further enables the determination of the imaginary part of the ratio of the $\Delta U=0$ over $\Delta U=1$ matrix elements in charm decays, which we find to be $(0.65\pm 0.12)$. Within the standard model, the result proves the non-perturbative nature of the penguin contraction of tree operators in charm decays, similar to the known non-perturbative enhancement of $\Delta I=1/2$ over $\Delta I=3/2$ matrix elements in kaon decays, that is, the $\Delta I=1/2$ rule. As a guideline for future measurements, we show how to completely solve the most general parametrization of the $D\to P^{+}{P}^{-}$ system.

    hep-phJHEP(2019)·104 citations
14. 14*

    Emergent QCD Kondo effect in two-flavor color superconducting phase

    Koichi Hattori🇯🇵 · Xu-Guang Huang🇨🇳 · Robert D. Pisarski🇺🇸

    We show that effective coupling strengths between ungapped and gapped quarks in the two-flavor color superconducting (2SC) phase are renormalized by logarithmic quantum corrections. We obtain a set of coupled renormalization-group (RG) equations for two distinct effective coupling strengths arising from gluon exchanges carrying different color charges. The diagram of RG flow suggests that both of the coupling strengths evolve into a strong-coupling regime as we decrease the energy scale toward the Fermi surface. This is a characteristic behavior observed in the Kondo effect, which has been known to occur in the presence of impurity scatterings via non-Abelian interactions. We propose a novel Kondo effect emerging without doped impurities, but with the gapped quasiexcitations and the residual SU(2) color subgroup intrinsic in the 2SC phase, which we call the 2SC Kondo effect.

    hep-phcond-mat.str-elhep-thPRD(2019)·16 citations
15. 15*

    Rank-One Flavor Violation and B-meson anomalies

    Valerio Gherardi🇮🇹 · David Marzocca🇮🇹 · Marco Nardecchia🇮🇹 · Andrea Romanino🇮🇹

    We assume that the quark-flavor coefficients matrix of the semileptonic operators addressing the neutral-current B-meson anomalies has rank-one, i.e. it can be described by a single vector in quark-flavor space. By correlating the observed anomalies to other flavor and high-$p_T$ observables, we constrain its possible directions and we show that a large region of the parameter space of this framework will be explored by flavor data from the NA62, KOTO, LHCb and Belle II experiments.

    hep-phhep-exJHEP(2019)·30 citations
16. 16*

    Production of Purely Gravitational Dark Matter: The Case of Fermion and Vector Boson

    Yohei Ema🇩🇪 · Kazunori Nakayama🇯🇵 · Yong Tang🇯🇵

    We consider the simplest possibility for a model of particle dark matter in which dark matter has only gravitational interaction with the standard model sector. Even in such a case, it is known that the gravitational particle production in an expanding universe may lead to a correct relic abundance depending on the inflation scale and the mass of dark matter particle. We provide a comprehensive and systematic analysis of the gravitational particle production of fermionic and vectorial dark matter, and emphasize that particles which are much heavier than the Hubble parameter but lighter than inflaton can also be produced abundantly.

    hep-phastro-ph.COJHEP(2019)·210 citations
17. 17*

    Squark-pair annihilation into quarks at next-to-leading order

    S. Schmiemann🇩🇪 · J. Harz🇩🇪 · B. Herrmann🇫🇷 · M. Klasen🇩🇪 · K. Kovařík🇩🇪

    The Minimal Supersymmetric Standard Model (MSSM) is under intense scrutiny at the LHC and in dark matter searches. Interestingly, scenarios with light squarks of the third generation remain not only viable, but also well motivated by the observed Standard-Model-like Higgs boson mass and dark matter relic density. The latter often requires important contributions from squark pair annihilation. Following up on previous work, we present in this paper a precision analysis of squark pair annihilation into quarks at next-to-leading order of QCD including Sommerfeld enhancement effects. We discuss all technical details of our one-loop, real emission and resummation calculations, their implementation in the precision tool DM@NLO, as well as the numerical impact on the annihilation cross section and cosmological relic density in phenomenological MSSM scenarios respecting in particular current LHC constraints. We demonstrate that including these radiative corrections leads to substantial shifts in the preferred parameter regions by up to 20 GeV.

    hep-phPRD(2019)·21 citations
18. 18*

    Possible interpretations of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$

    Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳 · Shi-Lin Zhu🇨🇳

    Based on our previous QCD sum rule studies on hidden-charm pentaquark states, we discuss possible interpretations of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$, which were recently observed by LHCb. Our results suggest that the $P_c(4312)$ can be well interpreted as the $[{\Sigma }_c^{++}{\bar{D}}^{-}]$ bound state with $J^P=1/2^{-}$, while the $P_c(4440)$ and $P_c(4457)$ can be interpreted as the $[{\Sigma }_c^{+}{\bar{D}}^0]$ bound state with $J^P=1/2^{-}$, the $[{\Sigma }_c^{\ast ++}{\bar{D}}^{-}]$ and $[{\Sigma }_c^{+}{\bar{D}}^{\ast 0}]$ bound states with $J^P=3/2^{-}$, or the $[{\Sigma }_c^{\ast +}{\bar{D}}^{\ast 0}]$ bound state with $J^P=5/2^{-}$. We propose to measure their spin-parity quantum numbers to verify these assignments.

    hep-phhep-exPRD(2019)·200 citations
19. 19*

    Strong LHCb evidence supporting the existence of the hidden-charm molecular pentaquarks

    Rui Chen🇨🇳 · Zhi-Feng Sun🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    On March 26th, 2019, at the Rencontres de Moriond QCD conference, the LHCb Collaboration reported the observation of three new pentaquarks, namely $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, which are consistent with the loosely bound molecular hidden-charm pentaquark states composed of an S-wave charmed baryon ${\Sigma }_c$ and an S-wave anti-charmed meson ($\bar{D},{\bar{D}}^{\ast }$). In this work, we present a direct calculation by the one-boson-exchange (OBE) model and demonstrate explicitly that the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ do correspond to the loosely bound ${\Sigma }_c\bar{D}$ with $(I=1/2,J^P=1/2^{-})$, ${\Sigma }_c{\bar{D}}^{\ast }$ with $(I=1/2,J^P=1/2^{-})$ and ${\Sigma }_c{\bar{D}}^{\ast }$ with $(I=1/2,J^P=3/2^{-})$, respectively.

    hep-phhep-exhep-latnucl-thPRD(2019)·261 citations
20. 20*

    SUSY discovery prospects with MoEDAL

    K. Sakurai🇵🇱 · D. Felea🇷🇴 · J. Mamuzic🇪🇸 · N. E. Mavromatos🇬🇧 · V. A. Mitsou🇪🇸 · J. L. Pinfold🇨🇦 · R. Ruiz de Austri🇪🇸 · A. Santra🇪🇸 · O. Vives🇪🇸

    We present a preliminary study on the possibility to search for massive long-lived electrically charged particles at the MoEDAL detector. MoEDAL is sensitive to highly ionising objects such as magnetic monopoles or massive (meta-)stable electrically charged particles and we focus on the latter in this paper. Requirements on triggering or reducing the cosmic-ray and cavern background, applied in the ATLAS and CMS analyses for long-lived particles, are not necessary at MoEDAL, due to its completely different detector design and extremely low background. On the other hand, MoEDAL requires slow-moving particles, resulting in sensitivity to massive states with typically small production cross sections. Using Monte Carlo simulations, we compare the sensitivities of MoEDAL versus ATLAS/CMS for various long-lived particles in supersymmetric models, and we seek a scenario where MoEDAL can provide discovery reach complementary to ATLAS and CMS.

    hep-phJ.Phys.Conf.Ser.(2020)·23 citations
21. 21*

    Off-shell single-top-quark production in the Standard Model Effective Field Theory

    Tobias Neumann🇺🇸 · Zack Sullivan🇺🇸

    We present a fully differential and spin-dependent $t$-channel single-top-quark calculation at next-to-leading order (NLO) in QCD including off-shell effects by using the complex mass scheme in the Standard Model (SM) and in the Standard Model Effective Field Theory (SMEFT). We include all relevant SMEFT operators at $1/{\Lambda }^2$ that contribute at NLO in QCD for a fully consistent comparison to the SM at NLO. In addition, we include chirality flipping operators that do not interfere with the SM amplitude and contribute only at $1/{\Lambda }^4$ with a massless $b$-quark. Such higher order effects are usually captured by considering anomalous right-handed $Wtb$ and left-handed $Wtb$ tensor couplings. Despite their formal suppression in the SMEFT, they describe an important class of models for new physics. Our calculation and analysis framework is publicly available in MCFM.

    hep-phhep-exJHEP(2019)·33 citations
22. 22*

    BHLS${}_2$, a New Breaking of the HLS Model and its Phenomenology

    M. Benayoun🇫🇷 · L. DelBuono🇫🇷 · F. Jegerlehner🇩🇪

    Previous studies have shown that the Hidden Local Symmetry (HLS) Model, supplied with appropriate symmetry breaking, provides an Effective Lagrangian (BHLS) able to encompass a large number of processes within a unified framework. A global fit provides a simultaneous description of the $e^{+}{e}^{-}$ annihilation into ${\pi }^{+}{\pi }^{-}$, ${\pi }^0\gamma$, $\eta \gamma$, ${\pi }^{+}{\pi }^{-}{\pi }^0$, $K^{+}{K}^{-}$, $K_L{K}_S$, the dipion spectrum in the $\tau$ decay and other light meson partial widths. Additional breaking schemes extend its scope to spacelike processes within a new framework (BHLS${}_2$). The phenomenology previously explored with BHLS is revisited in the BHLS${}_2$ context with emphasis on the $\Phi$ mass region. It is shown that BHLS${}_2$ addresses the close spacelike region covered by NA7 and Fermilab data; also,the Lattice QCD pion form factor is accurately predicted by BHLS${}_2$ using fits to annihilation data only. These channels contribution to $a_{\mu }$ over the range of validity of BHLS${}_2$ is shown to strongly reduce the former BHLS systematics. The uncertainty on $a_{\mu }^{\mathrm{th}}(\sqrt{s}<1.05$ GeV) is much improved compared to standard approaches relying on direct integration methods of measured spectra. Using the BHLS${}_2$ results, the leading order HVP contribution to the muon anomalous moment is $a_{\mu }^{HVP-LO}=686.65\pm 3.01+(+1.16,-0.75{)}_{syst.}$ in units of $10^{-10}$. Using a conservative estimate for the light--by--light contribution, our evaluation is $a_{\mu }^{\mathrm{th}}=\left[11659175.96\pm 4.17+(+1.16,-0.75{)}_{syst.}\right]\times 10^{-10}$. The ${\rho }^0\gamma$ mixing in dispersive and LQCD approaches is discussed and may amount to a shift $\delta a_{\mu }[\pi \pi {]}_{\rho \gamma }=+(3.10\pm 0.31)\times 10^{-10}$ at LO+NLO, presently treated as additional systematics. Taking this shift into account, $a_{\mu }^{\mathrm{th}}-a_{\mu }^{\mathrm{BNL}}$ exhibits a significance not smaller than $3.8\sigma$.

    hep-phEPJC(2020)·44 citations
23. 23*

    Polarisation of high energy gamma-rays after scattering

    Celine Boehm🇦🇺 · Andres Olivares-Del Campo🇬🇧 · Maura Ramirez-Quezada🇬🇧 · Ye-ling Zhou🇬🇧

    The polarisation of sunlight after scattering off the atmosphere was first described by Chandrasekhar using a geometrical description of Rayleigh interactions. Kosowsky later extended Chandrasekhar's formalism by using Quantum Field Theory (QFT) to describe the polarisation of the Cosmological Microwave Background radiation. Here we focus on a case that is rarely discussed in the literature, namely the polarisation of high energy radiation after scattering off particles. After demonstrating why the geometrical and low energy QFT approaches fail in this case, we establish the transport formalism that allows to describe the change of polarisation of high energy photons when they propagate through space or the atmosphere. We primarily focus on Compton interactions but our approach is general enough to describe e.g. the scattering of high energy photons off new particles or through new interactions. Finally we determine the conditions for a circularly polarised $\gamma$--ray signal to keep the same level of circular polarisation as it propagates through its environment.

    hep-phastro-ph.COastro-ph.HEJCAP(2019)·4 citations
24. 24*

    Dark-matter-nucleus scattering in chiral effective field theory

    Martin Hoferichter🇺🇸 · Philipp Klos🇩🇪 · Javier Menéndez🇯🇵 · Achim Schwenk🇩🇪

    Chiral effective field theory allows one to calculate the response of few-nucleon systems to external currents, both for currents that can be probed in the Standard Model and ones that only exist in Standard-Model extensions. In combination with state-of-the-art many-body methods, the constraints from chiral symmetry can then be implemented in nuclear structure factors that describe the response of atomic nuclei in direct-detection searches for dark matter. We review the present status of this approach, including the role of coherently enhanced two-body currents, the discrimination of dark matter candidates based on the nuclear response functions, and limits on Higgs-portal dark matter.

    hep-phhep-exhep-latnucl-thPoS(2019)·8 citations
25. 25*

    Universal Approximations for Flavor Models

    Gero von Gersdorff🇧🇷

    We develop a systematic analytical approximation scheme for the singular value decompositions of arbitrary complex three dimensional matrices Y with non-degenerate singular values. We derive exact expressions for the errors of this approximation and show that they are bounded from above by very simple ratios of the form (yi/yj)2n where yi < yj are singular values of Y and n is the order of the approximation. The applications we have in mind are the analytical and numerical treatments of arbitrary theories of flavor. We also compute upper bounds for the errors of the Cabbibo Kobayashi Maskawa (CKM) matrix that only depend on the ratios of the masses and the physical CKM angles.

    hep-phJHEP(2019)·7 citations
26. 26*

    One-loop Angularity Distributions with Recoil using Soft-Collinear Effective Theory

    Ankita Budhraja🇮🇳 · Ambar Jain🇮🇳 · Massimiliano Procura🇦🇹

    Angularities are event shapes whose sensitivity to the splitting angle of a collinear emission is controlled by a continuous parameter $b$, with $-1<b<\infty$. When measured with respect to the thrust axis, this class of QCD observables includes thrust ($b=1$) and jet broadening ($b=0$), the former being insensitive to the recoil of soft against collinear radiation, while the latter being maximally sensitive to it. Presently available analytic results for angularity distributions with $b\ne 0$ can be applied only close to the thrust limit since recoil effects have so far been neglected. As a first step to establish a comprehensive theoretical framework based on Soft-Collinear Effective Theory valid for all recoil-sensitive angularities, we compute for the first time angularity distributions at one-loop order in ${\alpha }_s$ for all values of $b$ taking into account recoil effects. In the differential cross section, these amount to novel sub-leading singular contributions and/or power corrections, where the former are characterized by fractional powers of the angularity and contribute appreciably close to the peak region, also for $b\gtrsim 0.5$. Our calculations are checked against various limits known in the literature and agree with the numerical output of the Event2 generator.

    hep-phJHEP(2019)·17 citations
27. 27*

    Fermi-LAT Observations of Gamma-Ray Emission Towards the Outer Halo of M31

    Chris Karwin🇺🇸 · Simona Murgia🇺🇸 · Sheldon Campbell🇺🇸 · Igor Moskalenko🇺🇸

    The Andromeda Galaxy is the closest spiral galaxy to us and has been the subject of numerous studies. It harbors a massive dark matter (DM) halo which may span up to ~600 kpc across and comprises ~90% of the galaxy's total mass. This halo size translates into a large diameter of 42 degrees on the sky for an M31-Milky Way (MW) distance of 785 kpc, but its presumably low surface brightness makes it challenging to detect with gamma-ray telescopes. Using 7.6 years of Fermi Large Area Telescope (Fermi-LAT) observations, we make a detailed study of the gamma-ray emission between 1-100 GeV towards M31's outer halo, with a total field radius of 60 degrees centered at M31, and perform an in-depth analysis of the systematic uncertainties related to the observations. We use the cosmic ray (CR) propagation code GALPROP to construct specialized interstellar emission models (IEMs) to characterize the foreground gamma-ray emission from the MW, including a self-consistent determination of the isotropic component. We find evidence for an extended excess that appears to be distinct from the conventional MW foreground, having a total radial extension upwards of ~120-200 kpc from the center of M31. We discuss plausible interpretations of the excess emission but emphasize that uncertainties in the MW foreground, and in particular, modeling of the H I-related components, have not been fully explored and may impact the results.

    ↳ astro-ph.HEhep-phPoS(2021)·21 citations
28. 28*

    Electromagnetic finite-size effects to the hadronic vacuum polarization

    J. Bijnens🇸🇪 · J. Harrison🇬🇧 · N. Hermansson-Truedsson🇸🇪 · T. Janowski🇬🇧 · A. Jüttner🇬🇧 · A. Portelli🇬🇧

    In order to reduce the current hadronic uncertainties in the theory prediction for the anomalous magnetic moment of the muon, lattice calculations need to reach sub-percent accuracy on the hadronic-vacuum-polarization contribution. This requires the inclusion of $\mathcal{O}(\alpha )$ electromagnetic corrections. The inclusion of electromagnetic interactions in lattice simulations is known to generate potentially large finite-size effects suppressed only by powers of the inverse spatial extent. In this paper we derive an analytic expression for the ${\mathrm{QED}}_{\mathrm{L}}$ finite-volume corrections to the two-pion contribution to the hadronic vacuum polarization at next-to-leading order in the electromagnetic coupling in scalar QED. The leading term is found to be of order $1/L^3$ where $L$ is the spatial extent. A $1/L^2$ term is absent since the current is neutral and a photon far away thus sees no charge and we show that this result is universal. Our analytical results agree with results from the numerical evaluation of loop integrals as well as simulations of lattice scalar $U(1)$ gauge theory with stochastically generated photon fields. In the latter case the agreement is up to exponentially suppressed finite-volume effects. For completeness we also calculate the hadronic vacuum polarization in infinite volume using a basis of 2-loop master integrals.

    ↳ hep-lathep-phPRD(2019)·30 citations
29. 29*

    Further Theoretical Analysis on the $K^{-}{}^3\text{He}\to \Lambda pn$ Reaction for the $\bar{K}NN$ Bound-State Search in the J-PARC E15 Experiment

    Takayasu Sekihara (JAEA, Ibaraki)🇯🇵 · Eulogio Oset (Valencia U. & Valencia U., IFIC)🇪🇸 · Angels Ramos (Barcelona U., ECM & ICC, Barcelona U.)🇪🇸

    Based on the scenario that a $\bar{K}NN$ bound state is generated and it eventually decays into $\Lambda p$, we calculate the cross section of the $K^{-}{}^3\text{He}\to \Lambda pn$ reaction, which was recently measured in the J-PARC E15 experiment. We find that the behavior of the calculated differential cross section $d^2\sigma /d{M}_{\Lambda p}d{q}_{\Lambda p}$, where $M_{\Lambda p}$ and $q_{\Lambda p}$ are the $\Lambda p$ invariant mass and momentum transfer in the $(K^{-},n)$ reaction in the laboratory frame, respectively, is consistent with the experiment. Furthermore, we can reproduce almost quantitatively the experimental data of the $\Lambda p$ invariant mass spectrum in the momentum transfer window $350\text{ MeV}/c<q_{\Lambda p}<650\text{ MeV}/c$. These facts strongly suggest that the $\bar{K}NN$ bound state was indeed generated in the J-PARC E15 experiment.

    ↳ nucl-thhep-phnucl-exJPS Conf.Proc.(2019)·5 citations
30. 30*

    Six-Gluon Amplitudes in Planar $\mathcal{N}=4$ Super-Yang-Mills Theory at Six and Seven Loops

    Simon Caron-Huot🇨🇦 · Lance J. Dixon🇺🇸 · Falko Dulat🇺🇸 · Matt von Hippel🇩🇰 · Andrew J. McLeod🇩🇰 · Georgios Papathanasiou🇩🇪

    We compute the six-particle maximally-helicity-violating (MHV) and next-to-MHV (NMHV) amplitudes in planar maximally supersymmetric Yang-Mills theory through seven loops and six loops, respectively, as an application of the extended Steinmann relations and using the cosmic Galois coaction principle. Starting from a minimal space of functions constructed using these principles, we identify the amplitude by matching its symmetries and predicted behavior in various kinematic limits. Through five loops, the MHV and NMHV amplitudes are uniquely determined using only the multi-Regge and leading collinear limits. Beyond five loops, the MHV amplitude requires additional data from the kinematic expansion around the collinear limit, which we obtain from the Pentagon Operator Product Expansion, and in particular from its single-gluon bound state contribution. We study the MHV amplitude in the self-crossing limit, where its singular terms agree with previous predictions. Analyzing and plotting the amplitudes along various kinematical lines, we continue to find remarkable stability between loop orders.

    ↳ hep-thhep-phJHEP(2019)·201 citations
31. 31*

    Spectral properties of light and charm mesons from $N_f=2+1$ anisotropic lattice QCD

    Ryan Quinn🇮🇪 · Jonas Glesaaen🇬🇧 · Alexander Rothkopf🇳🇴 · Jon-Ivar Skullerud🇮🇪

    We compute temporal correlators and spectral functions for light, open charm and charmonium mesons in the pseudoscalar and vector channel for a range of temperatures below and above the deconfinement transition. The study is carried out using anisotropic lattice QCD with 2+1 dynamical flavours, $a_s=0.123$fm and $a_s/a_{\tau }=3.5$. The high-temperature results are benchmarked by comparing them to reconstructed correlators obtained by direct summation of the zero temperature correlator. We use two Bayesian methods to reconstruct the spectral functions: the maximum entropy method and the more recent BR method.

    ↳ hep-lathep-phPoS(2019)·4 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.