Wed·Jun 20, 2018Wednesday·June 20, 2018

1. 01*

   Observationally inferred dark matter phase-space distribution and direct detection experiments

   Sayan Mandal🇺🇸 · Subhabrata Majumdar🇮🇳 · Vikram Rentala🇮🇳 · Ritoban Basu Thakur🇺🇸

   We present a detailed analysis of the effect of an observationally determined dark matter (DM) velocity distribution function (VDF) of the Milky Way (MW) on DM direct detection rates. We go beyond local kinematic tracers and use rotation curve data up to 200 kpc to construct a MW mass model and self-consistently determine the local phase-space distribution of DM. This approach mitigates any incomplete understanding of local dark matter-visible matter degeneracies that can affect the determination of the VDF. Comparing with the oft used Standard Halo Model (SHM), which assumes an isothermal VDF, we look at how the tail of the empirically determined VDF alters our interpretation of the present direct detection WIMP DM cross section exclusion limits. While previous studies have suggested a very large difference (of more than an order of magnitude) in the bounds at low DM masses, we show that accounting for the detector response at low threshold energies, the difference is still significant although less extreme. The change in the number of signal events, when using the empirically determined DM VDF in contrast to the SHM VDF, is most prominent for low DM masses for which the shape of the recoil energy spectrum depends sensitively on the detector threshold energy as well as detector response near the threshold. We demonstrate that these trends carry over to the respective DM exclusion limits, modulo detailed understanding of the experimental backgrounds. With the unprecedented precision of astrometric data in the GAIA era, use of observationally determined DM phase-space will become a critical and necessary ingredient for DM searches. We provide an accurate fit to the current best observationally determined DM VDF (and self-consistent local DM density) for use in analyzing current DM direct detection data by the experimental community.

   hep-phastro-ph.GAhep-exPRD(2019)·17 citations
2. 02*

   Can the symmetry breaking in the SM be determined by the "second minimum" of the Higgs potential?

   Alejandro Cabo · Jose Carlos Suarez · Denys Arrebato🇨🇺 · Fernando Guzman🇨🇺 · Jorge Luis Acosta🇨🇺

   The possibility that the spontaneous symmetry breaking in the Standard Model (SM) may be generated by the Top-Higgs Yukawa interaction (which determines the so called "second minimum" in the SM) is examined. A former analysis is extended about a QCD action only including the Yukawa interaction of a single quark with a scalar field. We repeat the calculation of the two loop effective action of the model for the scalar field. A correction of the evaluation allowed choosing a strong coupling $\alpha$($\mu ,{\Lambda }_{QCD})=0.2254$ GeV at an intermediate scale $\mu =11.63$ GeV, in order to fix the minimum of the potential at a scalar field determining $175$ GeV for the quark mass. A scalar field mass $m=44$ GeV is following, which is of the order than the experimental Higgs mass. The effects of considering a running with momenta coupling are studied. For this, the finite part of the two loop potential contribution determined by the strong coupling, was represented as a momentum integral. Next, substituting in this integral the experimental values of the running coupling, the potential curve became very similar to the one for constant coupling. This happened after simply assuming that the low momentum dependence of the coupling is "saturated" to a constant value being close to its lowest experimental value.

   hep-phhep-thLHEP(2019)·0 citations
3. 03*

   The $\beta$-function for Yukawa theory at large $N_f$

   Tommi Alanne🇩🇪 · Simone Blasi🇩🇪

   We compute the $\beta$-function for a massless Yukawa theory in a closed form at the order $\mathcal{O}(1/N_f)$ in the spirit of the expansion in a large number of flavours $N_f$. We find an analytic expression with a finite radius of convergence, and the first singularity occurs at the coupling value $K=5$.

   hep-phhep-thJHEP(2018)·15 citations
4. 04*

   Closing the Gap on $R_{D^{\ast }}$ by including longitudinal effects

   J. E. Chavez-Saab🇲🇽 · Genaro Toledo🇲🇽

   Measurements of the $R_{D^{\ast }}\equiv \mathrm{Br}(B\to \tau \nu D^{\ast })/\mathrm{Br}(B\to e\nu D^{\ast })$ parameter remain in tension with the standard model prediction, despite recent results helping to close the gap. The standard model prediction it is compared with considers the $D^{\ast }$ as an external particle, even though what is detected in experiments is a $D\pi$ pair it decays into, from which it is reconstructed. We argue that the experimental result must be compared with the theoretical prediction considering the full 4-body decay $(B\to l\nu D^{\ast }\to l\nu D\pi )$. We show that the longitudinal degree of freedom of the off-shell $D^{\ast }$ helps to further close the disagreement gap with experimental data. We find values for the ratio $R_{D\pi }^l\equiv \mathrm{Br}(B\to \tau {\nu }_{\tau }D\pi )/\mathrm{Br}(B\to l{\nu }_{l}D\pi )$ of $R_{D\pi }^e=0.274\pm 0.003$ and $R_{D\pi }^{\mu }=0.275\pm 0.003$, where the uncertainty comes from the uncertainty of the form factors parameters. Comparing against $R_{D\pi }$ reduces the gap with the latest LHCb result from $1.1\sigma$ to $0.48\sigma$, while the gap with the latest Belle result is reduced from $0.42\sigma$ to just $0.10\sigma$ and with the world average results from $3.7\sigma$ to $2.1\sigma$. Erratum added at the end of the file.

   hep-phPRD(2018)·3 citations
5. 05*

   Limit on the Axion Decay Constant from the Cooling Neutron Star in Cassiopeia A

   Koichi Hamaguchi🇯🇵 · Natsumi Nagata🇯🇵 · Keisuke Yanagi🇯🇵 · Jiaming Zheng🇯🇵

   The observed rapid cooling of the neutron star (NS) located at the center of the supernova remnant Cassiopeia A (Cas A) can be explained in the minimal NS cooling scenario. This consequence may be changed if there exists an extra cooling source, such as axion emission. In this work, we study the Cas A NS cooling in the presence of axion emission, taking account of the temperature evolution in the whole life of the Cas A NS. We obtain a lower limit on the axion decay constant, $f_a\gtrsim (5-7)\times 10^8$ GeV, if the star has an envelope with a thin carbon layer. This is as strong as existing limits imposed by other astrophysical observations such as SN1987A.

   hep-phastro-ph.HEPRD(2018)·132 citations
6. 06*

   Jet quenching parameter in an expanding QCD plasma

   Edmond Iancu🇫🇷 · Pieter Taels🇮🇹 · Bin Wu🇨🇭

   We study the phenomenon of transverse momentum broadening for a high-$p_T$ parton propagating through a weakly-coupled quark-gluon plasma undergoing boost-invariant longitudinal expansion. We propose a boost-invariant description for this phenomenon, in which the broadening refers to the angular variables $\eta$ (the pseudo-rapidity) and $\varphi$ (the azimuthal angle). The jet quenching parameter $\hat{q}$ which enters this description depends upon the proper time alone. We furthermore consider radiative corrections to $\hat{q}$. As in the case of a static medium, we find potentially large corrections enhanced by a double logarithm. But unlike for the static medium, these corrections are now local in time: they depend upon the local (proper) time characterizing the expansion, and not upon the overall path length. We resum such corrections to all orders into a renormalized jet quenching parameter. The main effect of this resummation is to slow down the decrease of $\hat{q}$ with increasing proper time.

   hep-phhep-exnucl-exnucl-thPLB(2018)·25 citations
7. 07*

   A Linear seesaw model with hidden gauge symmetry

   Takaaki Nomura🇰🇷 · Hiroshi Okada🇰🇷

   We propose a natural realization of linear seesaw model with hidden gauge symmetry in which $SU(2{)}_L$ triplet fermions, one extra Higgs singlet, doublet and quartet scalar are introduced. Small neutrino mass can be realized by two suppression factors that are small vacuum expectation value of quartet scalar and inverse of Dirac mass for triplet. After formulating neutrino mass matrix, we discuss collider phenomenology of the model focusing on signals from exotic charged particles production at the LHC.

   hep-phPRD(2019)·19 citations
8. 08*

   Equivalent photons in proton-proton and ion-ion collisions at the LHC

   Mikhail Vysotsky🇷🇺 · Evgeny Zhemchugov🇷🇺

   Equivalent photon approximation is used to calculate fiducial cross sections for dimuon production in ultraperipheral proton-proton and lead-lead collisions. Analytical formulae taking into account experimental cuts are derived. The results are compared with the measurements reported by the ATLAS collaboration.

   hep-phhep-exPhys.Usp.(2019)·45 citations
9. 09*

   High-dimensional neutrino masses

   G. Anamiati🇪🇸 · Oscar Castillo-Felisola🇨🇱 · Renato M. Fonseca🇨🇿 · J. C. Helo🇨🇱 · M. Hirsch🇪🇸

   For Majorana neutrino masses the lowest dimensional operator possible is the Weinberg operator at $d=5$. Here we discuss the possibility that neutrino masses originate from higher dimensional operators. Specifically, we consider all tree-level decompositions of the $d=9$, $d=11$ and $d=13$ neutrino mass operators. With renormalizable interactions only, we find 18 topologies and 66 diagrams for $d=9$, and 92 topologies plus 504 diagrams at the $d=11$ level. At $d=13$ there are already 576 topologies and 4199 diagrams. However, among all these there are only very few genuine neutrino mass models: At $d=(9,11,13)$ we find only (2,2,2) genuine diagrams and a total of (2,2,6) models. Here, a model is considered genuine at level $d$ if it automatically forbids lower order neutrino masses {\em without} the use of additional symmetries. We also briefly discuss how neutrino masses and angles can be easily fitted in these high-dimensional models.

   hep-phJHEP(2018)·53 citations
10. 10*

    A model to accommodate the $B$-physics anomalies

    Damir Becirevic🇫🇷

    After briefly reviewing the status of the $B$-physics anomalies, describing the challenges of building a scenario of physics beyond the Standard Model that can accommodate the observed departures from lepton flavor universality, I discuss a new model, based on extending the Standard Model by two light [$\mathcal{O}(1\mathrm{TeV})$] scalar leptoquarks. That model, in addition to satisfying a number of flavor physics constraints both at low and high energies, also allows for a $SU(5)$ unification.

    hep-phhep-exhep-lat1 citation
11. 11*

    Inclusive jet production as a probe of polarized PDFs at a future EIC

    Radja Boughezal🇺🇸 · Frank Petriello🇺🇸 · Hongxi Xing🇺🇸

    We present a detailed phenomenological study of polarized inclusive jet production in electron-proton collisions at a future Electron-Ion Collider (EIC). Our analysis is performed at next-to-leading order in perturbative QCD using the numerical code DISTRESS and includes all relevant partonic channels and resolved photon contributions. We elucidate the role of different kinematic regions in probing different aspects of proton and photon structure and study the impact of the EIC collision energy on the measurement of polarized parton distribution functions.

    hep-phnucl-exnucl-thPRD(2018)·31 citations
12. 12*

    Simulations of photo-nuclear dijets with Pythia 8 and their sensitivity to nuclear PDFs

    Ilkka Helenius🇩🇪

    In ultra-peripheral heavy-ion collisions the nuclei pass with such a large impact parameter that no strong interaction can take place. However, a photon emitted by one nucleus can still interact either with the other nucleus or with a photon from the another nucleus. The former event type corresponds to photoproduction, earlier studied e.g. in electron-proton collisions at HERA, but now with a nuclear target. This provides an unique opportunity to study the nuclear modifications of the PDFs with the photo-nuclear processes measured in lead-lead collisions at the LHC. Here we present our recent implementation of photoproduction processes in the Pythia 8 general-purpose Monte-Carlo event generator. The resulting simulations are compared to charged-hadron and dijet photoproduction data from the HERA experiments, and the theoretical uncertainties of the framework are studied. We discuss how the relevant part of the photon flux from heavy ions is obtained using the equivalent photon approximation and present predictions for photo-nuclear dijet cross section at the LHC. To estimate the potential of this data to further constrain the nuclear PDFs, the expected statistical uncertainty based on LHC luminosity is compared to uncertainties in the current nuclear PDF analyses.

    hep-phPoS(2018)·13 citations
13. 13*

    Radiative instability of quantum electrodynamics in chiral matter

    Kirill Tuchin🇺🇸

    Modification of the photon dispersion relation in chiral matter enables $1\to 2$ scattering. As a result, the single fermion and photon states are unstable to photon radiation and pair production respectively. In particular, a fast fermion moving through chiral matter can spontaneously radiate a photon, while a photon can spontaneously radiate a fast fermion and anti-fermion pair. The corresponding spectra are derived in the ultra-relativistic approximation. It is shown that the polarization of the produced and decayed photons is determined by the sign of the chiral conductivity. Impact of a flat thin domain wall on the spectra is computed.

    hep-phnucl-thPLB(2018)·25 citations
14. 14*

    Long-Lived Particles at the Energy Frontier: The MATHUSLA Physics Case

    David Curtin🇨🇦 · Marco Drewes🇧🇪 · Matthew McCullough🇨🇭 · Patrick Meade🇺🇸 · Rabindra N. Mohapatra🇺🇸 · Jessie Shelton🇺🇸 · Brian Shuve🇺🇸 · Elena Accomando🇬🇧 · Cristiano Alpigiani🇺🇸 · Stefan Antusch🇨🇭 · Juan Carlos Arteaga-Velázquez🇲🇽 · Brian Batell🇺🇸 and 76 other authors

    We examine the theoretical motivations for long-lived particle (LLP) signals at the LHC in a comprehensive survey of Standard Model (SM) extensions. LLPs are a common prediction of a wide range of theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, and represent a natural and generic possibility for physics beyond the SM (BSM). In most cases the LLP lifetime can be treated as a free parameter from the $\mu$m scale up to the Big Bang Nucleosynthesis limit of $\sim 10^7$m. Neutral LLPs with lifetimes above $\sim$ 100m are particularly difficult to probe, as the sensitivity of the LHC main detectors is limited by challenging backgrounds, triggers, and small acceptances. MATHUSLA is a proposal for a minimally instrumented, large-volume surface detector near ATLAS or CMS. It would search for neutral LLPs produced in HL-LHC collisions by reconstructing displaced vertices (DVs) in a low-background environment, extending the sensitivity of the main detectors by orders of magnitude in the long-lifetime regime. In this white paper we study the LLP physics opportunities afforded by a MATHUSLA-like detector at the HL-LHC. We develop a model-independent approach to describe the sensitivity of MATHUSLA to BSM LLP signals, and compare it to DV and missing energy searches at ATLAS or CMS. We then explore the BSM motivations for LLPs in considerable detail, presenting a large number of new sensitivity studies. While our discussion is especially oriented towards the long-lifetime regime at MATHUSLA, this survey underlines the importance of a varied LLP search program at the LHC in general. By synthesizing these results into a general discussion of the top-down and bottom-up motivations for LLP searches, it is our aim to demonstrate the exceptional strength and breadth of the physics case for the construction of the MATHUSLA detector.

    hep-phhep-exRept.Prog.Phys.(2019)·564 citations
15. 15*

    Manifestly Soft Gauge Invariant Formulation of vNRQCD

    Ira Z. Rothstein🇺🇸 · Prashant Shrivastava🇺🇸 · Iain W. Stewart🇺🇸

    Homogeneous power counting in Non-Relativistic QCD (NRQCD) implies the simultaneous existence of both soft and ultrasoft gluons. In the velocity renormalization group (vNRQCD) formalism we show that operators involving soft fields interacting with heavy potential quarks can be put in a manifestly gauge invariant form by utilizing gluon and quark building blocks which contain Wilson lines, and are analogous to those used in the soft collinear effective theory. This leads to several simplifications, in particular significantly reducing the size of the operator basis, which stream-lines matching and anomalous dimension calculations at subleading order in the velocity expansion. Also, soft ghosts no longer couple via potential like interactions to the heavy quark fields, and hence do not appear until two loops. Furthermore the the color structures that appear at each order in ${\alpha }_s$ in the static potential are only those which should arise according to non-Abelian exponentiation. We also discuss how zero-bin subtractions clarify the role of $i\epsilon$ terms in the heavy quark propagator poles carrying soft momenta. Even though the choice of the direction of the soft Wilson lines in our building blocks does not matter, there is still a limited set of consistent choices, and the predicted form of the eikonal poles does influence results at two-loops and beyond.

    hep-phnucl-thNPB(2019)·13 citations
16. 16*

    Combined Explanations of the $b\to s{\mu }^{+}{\mu }^{-}$ and $b\to c{\tau }^{-}\bar{\nu }$ Anomalies: a General Model Analysis

    Jacky Kumar🇮🇳 · David London🇨🇦 · Ryoutaro Watanabe🇨🇦

    There are four models of tree-level new physics (NP) that can potentially simultaneously explain the $b\to s{\mu }^{+}{\mu }^{-}$ and $b\to c{\tau }^{-}\bar{\nu }$ anomalies. They are the S3, U3 and U1 leptoquarks (LQs), and a triplet of SM-like vector bosons (VBs). Under the theoretical assumption that the NP couples predominantly to the third generation, previous analyses found that, when constraints from other processes are taken into account, the S3, U3 and VB models cannot explain the B anomalies, but U1 is viable. In this paper, we reanalyze these models, but without any assumption about their couplings. We find that, even in this most general case, S3 and U3 are excluded. For the U1 model, constraints from the semileptonic lepton-flavour-violating (LFV) processes $B\to K^{(\ast )}{\mu }^{\pm }{\tau }^{\mp }$, $\tau \to \mu \varphi$ and ${\rm Y}\to \mu \tau$, which have been largely ignored previously, are found to be very important. Because of the LFV constraints, the pattern of couplings of the U1 LQ is similar to that obtained with the above theoretical assumption. Also, the LFV constraints render unimportant those constraints obtained using the renormalization group equations. As for the VB model, it is excluded if the above theoretical assumption is made due to the additional constraints from $B_s^0$-${\bar{B}}_s^0$ mixing, $\tau \to 3\mu$ and $\tau \to \mu \nu \bar{\nu }$. By contrast, we find a different set of NP couplings that both explains the $b\to s{\mu }^{+}{\mu }^{-}$ anomaly and is compatible with all constraints. However, it does not reproduce the measured values of the $b\to c{\tau }^{-}\bar{\nu }$ anomalies -- it would be viable only if future measurements find that the central values of these anomalies are reduced. Even so, this VB model is excluded by the LHC bounds on high-mass resonant dimuon pairs. This conclusion is reached without any assumptions about the NP couplings.

    hep-phhep-exPRD(2019)·175 citations
17. 17*

    Dynamical gauge fields and anomalous transport at strong coupling

    Angel Domingo Gallegos🇳🇱 · Umut Gürsoy🇳🇱

    Anomalous transport coefficients are known to be universal in the absence of dynamical gauge fields. We calculate the corrections to these universal values due to dynamical gluon fields at strong coupling, at finite temperature and finite density, using the holographic duality. We show that the consistent chiral magnetic and chiral vortical currents receive no corrections, while we derive a semi-analytic formula for the chiral separation conductivity. We determine these corrections in the large color, large flavor limit, in terms of a series expansion in the anomalous dimension $\Delta$ of the axial current in terms of physical parameters $\Delta$, temperature, electric and chiral chemical potentials and the flavor to color ratio $\frac{N_f}{N_c}$. Our results are applicable to a generic class of chiral gauge theories that allow for a holographic description in the gravity approximation. We also determine the dynamical gluon corrections to the chiral vortical separation current in a particular example in the absence of external axial fields.

    ↳ hep-thcond-mat.str-elhep-phJHEP(2019)·13 citations
18. 18*

    Axion Detection with Precision Frequency Metrology

    Maxim Goryachev🇦🇺 · Ben McAllister🇦🇺 · Michael E. Tobar🇦🇺

    We investigate a new class of galactic halo axion detection techniques based on precision frequency and phase metrology. Employing equations of axion electrodynamics, it is demonstrated how a dual mode cavity exhibits linear mode-mode coupling mediated by the axion upconversion and axion downconversion processes. The approach demonstrates phase sensitivity with an ability to detect axion phase with respect to externally pumped signals. Axion signal to phase spectral density conversion is calculated for open and closed loop detection schemes. The fundamental limits of the proposed approach come from the precision of frequency and environment control electronics, rather than fundamental thermal fluctuations allowing for table-top experiments approaching state-of-the-art cryogenic axion searches in sensitivity. Practical realisations are considered, including a TE-TM mode pair in a cylindrical cavity resonator and two orthogonally polarised modes in a Fabry-Pérot cavity.

    ↳ physics.ins-detcond-mat.otherhep-exhep-ph+1Phys.Dark Univ.(2019)·47 citations
19. 19*

    Profile of a Galactic Spherical Cloud of Self-Gravitating Fermions

    B. G. Giraud🇫🇷 · R. Peschanski🇫🇷

    The field which binds a thermal fermionic cloud is defined as a Hartree integral upon its density. In turn, the density results from the field via a Thomas-Fermi occupation of the local phase space. This defines a complete theory of all properties and observables for the cloud. As an application to dark matter halos, comparisons with astronomic data on dwarf spheroidal galaxies are provided and discussed. Estimates of the elementary fermion mass are obtained, serving as a phase-space bound on fermionic dark matter.

    ↳ hep-thastro-ph.GAhep-phPhys.Scripta(2019)·8 citations
20. 20*

    Naturalness, Extra-Empirical Theory Assessments, and the Implications of Skepticism

    James D. Wells🇺🇸

    Naturalness is an extra-empirical quality that aims to assess plausibility of a theory. Finetuning measures are often deputized to quantify the task. However, knowing statistical distributions on parameters appears necessary. Such meta-theories are not known yet. A critical discussion of these issues is presented, including their possible resolutions in fixed points. Both agreement to and skepticism of naturalness's utility remains credible, as is skepticism to any extra-empirical theory assessment (SEETA) that claims to identify "more correct" theories that are equally empirically adequate. The severe implications of SEETA are set forward in some detail. We conclude with a summary and discussion of the viability of three main viewpoints toward naturalness and fine-tuning, where the "moderate naturalness position" is suggested to be most appealing, not suffering from the disquietudes of the extreme pro- and anti-naturalness positions.

    ↳ physics.hist-phhep-phhep-thFound.Phys.(2019)·22 citations
21. 21*

    Motion in time-periodic backgrounds with applications to ultralight dark matter haloes at galactic centers

    Mateja Bošković🇵🇹 · Francisco Duque🇵🇹 · Miguel C. Ferreira🇵🇹 · Filipe S. Miguel🇵🇹 · Vitor Cardoso🇵🇹

    We consider motion in spherically symmetric but time-dependent backgrounds. This problem is of interest, for example, in the context of ultralight dark matter, where galactic haloes produce a time-dependent and periodic gravitational potential. We study the properties of motion of stars in such spacetimes, for different field strengths and frequency, and including dissipative effects. We show that orbital resonances may occur and that spectroscopic emission lines from stars in these geometries exhibit characteristic, periodic modulation patterns. In addition, we work out a fully relativistic and weak-field description of a special class of time-periodic geometries, that of scalar oscillatons. When applied to the galactic center, our results indicate that the motion of S2-like stars may carry distinguishable observational imprints of ultra-light dark matter.

    ↳ gr-qcastro-ph.COastro-ph.GAhep-ph+1PRD(2018)·52 citations
22. 22*

    Quantum Gauge Transformation, Gauge-Invariant Extension and Angular Momentum Decomposition in Abelian Higgs Model

    Israel Weimin Sun🇨🇳

    I discuss the momentum and angular momentum decomposition problem in the Abelian Higgs model. The usual gauge-invariant extension (GIE) construction is incorporated naturally into the framework of quantum gauge transformation $\grave{a}$ $la$ Strocchi and Wightman and with this I investigate the momentum and angular momentum separation in a class of GIE conditions which correspond to the so-called "static gauges". Using this language I find that the so-called "generator criterion" does not generally hold even for the dressed physical field. In the case of $U(1)$ symmetry breaking, I generalize the standard GIE construction to include the matter field degrees of freedom so that the usual separation pattern of momentum and angular momentum in the unitarity gauge can be incorporated into the same universal framework. When the static gauge condition could not uniquely fix the gauge, I show that this GIE construction should be expanded to take into account the residual gauge symmetry. In some cases I reveal that the usual momentum or angular momentum separation pattern in terms of the physical dressed field variables needs some type of modification due to the nontrivial commutator structure of the underlying quantum gauge choice. Finally, I give some remarks on the general GIE constructions in connection with the possible commutator issues and modification of momentum and angular momentum separation patterns.

    ↳ hep-thhep-phMod.Phys.Lett.A(2018)·0 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.