Tue·Jun 27, 2017Tuesday·June 27, 2017

1. 01*

   Constraints on hidden gravitons from fifth-force experiments and stellar energy loss

   J. A. R. Cembranos🇪🇸 · A. L. Maroto🇪🇸 · H. Villarrubia-Rojo🇪🇸

   We study different phenomenological signatures associated with new spin-2 particles. These new degrees of freedom, that we call hidden gravitons, arise in different high-energy theories such as extra-dimensional models or extensions of General Relativity. At low energies, hidden gravitons can be generally described by the Fierz-Pauli Lagrangian. Their phenomenology is parameterized by two dimensionful constants: their mass and their coupling strength. In this work, we analyze two different sets of constraints. On the one hand, we study potential deviations from the inverse-square law on solar-system and laboratory scales. To extend the constraints to scales where the laboratory probes are not competitive, we also study consequences on astrophysical objects. We analyze in detail the processes that may take place in stellar interiors and lead to emission of hidden gravitons, acting like an additional source of energy loss.

   hep-phastro-ph.COastro-ph.HEgr-qcJHEP(2017)·23 citations
2. 02*

   Prospects for determining the particle/antiparticle nature of WIMP dark matter with direct detection experiments

   Bradley J. Kavanagh🇫🇷 · Farinaldo S. Queiroz🇩🇪 · Werner Rodejohann🇩🇪 · Carlos E. Yaguna🇨🇴

   It was recently pointed out that direct detection signals from at least three different targets may be used to determine whether the Dark Matter (DM) particle is different from its antiparticle. In this work, we examine in detail the feasibility of this test under different conditions, motivated by proposals for future detectors. Specifically, we perform likelihood fits to mock data under the hypotheses that the DM particle is identical to or different from its antiparticle, and determine the significance with which the former can be rejected in favor of the latter. In our analysis, we consider 3 different values of the DM mass ($50$ GeV, $300$ GeV, $1$ TeV) and 4 different experimental ensembles, each consisting of at least 3 different targets -- Xe and Ar plus one among the following: Si, Ge, $\mathrm{CaW}{\mathrm{O}}_4$, or Ge/$\mathrm{CaW}{\mathrm{O}}_4$. For each of these experimental ensembles and each DM mass, the expected discrimination significance is calculated as a function of the DM-nucleon couplings. In the best case scenario, the discrimination significance can reach $\mathcal{O}(3\sigma )$ for three of the four ensembles considered, and $\mathcal{O}(5\sigma )$ for the ensemble including $\mathrm{Si}$, highlighting the need for a variety of experimental targets in order to determine the DM properties. These results show that future direct detection signals could be used to exclude, at a statistically significant level, a Majorana or a real DM particle, giving a critical clue about the identity of the Dark Matter.

   hep-phastro-ph.HEJHEP(2017)·18 citations
3. 03*

   Deep learning approach to the Higgs boson CP measurement in H to tau tau decay and associated systematics

   Elisabetta Barberio🇦🇺 · Brian Le🇵🇱 · Elzbieta Richter-Was🇵🇱 · Zbigniew Was🇵🇱 · Daniele Zanzi🇦🇺 · Jakub Zaremba🇵🇱

   The H to tau tau decays form the prime channel for the measurement of the Higgs boson state and tests of the CP invariance of Higgs boson couplings. A previous study has shown the viability of deep learning techniques for the measurement. In this paper, the study is expanded. Effects due to the partial modelling of experimental effects are discussed. Furthermore, systematics due to ? decay modelling for complex cascade decays to tau^pm to a_1^pm nu_tau to rho^0 pi^pm nu_tau to 3pi^\pm nu_tau are also addressed. Various parameterisations are considered using low-energy collision data.

   hep-phPRD(2017)·19 citations
4. 04*

   Anapole dark matter annihilation into photons

   David C. Latimer🇺🇸

   In models of anapole dark matter (DM), the DM candidate is a Majorana fermion whose primary interaction with standard model (SM) particles is through an anapole coupling to off-shell photons. As such, at tree-level, anapole DM undergoes p-wave annihilation into SM charged fermions via a virtual photon. But, generally, Majorana fermions are polarizable, coupling to two real photons. This fact admits the possibility that anapole DM can annihilate into two photons in an s-wave process. Using an explicit model, we compute both the tree-level and diphoton contributions to the anapole DM annihilation cross section. Depending on model parameters, the s-wave process can either rival or be dwarfed by the p-wave contribution to the total annihilation cross section. Subjecting the model to astrophysical upper bounds on the s-wave annihilation mode, we rule out the model with large s-wave annihilation.

   hep-phhep-thPRD(2017)·18 citations
5. 05*

   The static hard-loop gluon propagator to all orders in anisotropy

   Mohammad Nopoush🇺🇸 · Yun Guo🇨🇳 · Michael Strickland🇺🇸

   We calculate the (semi-)static hard-loop self-energy and propagator using the Keldysh formalism in a momentum-space anisotropic quark-gluon plasma. The static retarded, advanced, and Feynman (symmetric) self-energies and propagators are calculated to all orders in the momentum-space anisotropy parameter $\xi$. For the retarded and advanced self-energies/propagators, we present a concise derivation and comparison with previously-obtained results and extend the calculation of the self-energies to next-to-leading order in the gluon energy, $\omega$. For the Feynman self-energy/propagator, we present new results which are accurate to all orders in $\xi$. We compare our exact results with prior expressions for the Feynman self-energy/propagator which were obtained using Taylor-expansions around an isotropic state. We show that, unlike the Taylor-expanded results, the all-orders expression for the Feynman propagator is free from infrared singularities. Finally, we discuss the application of our results to the calculation of the imaginary-part of the heavy-quark potential in an anisotropic quark-gluon plasma.

   hep-phnucl-thJHEP(2017)·39 citations
6. 06*

   Evaluating Feynman integrals by the hypergeometry

   Tai-Fu Feng🇨🇳 · Chao-Hsi Chang🇨🇳 · Jian-Bin Chen🇨🇳 · Zhi-Hua Gu🇨🇳 · Hai-Bin Zhang🇨🇳

   The hypergeometric function method naturally provides the analytic expressions of scalar integrals from concerned Feynman diagrams in some connected regions of independent kinematic variables, also presents the systems of homogeneous linear partial differential equations satisfied by the corresponding scalar integrals. Taking examples of the one-loop $B_{{}_0}$ and massless $C_{{}_0}$ functions, as well as the scalar integrals of two-loop vacuum and sunset diagrams, we verify our expressions coinciding with the well-known results of literatures. Based on the multiple hypergeometric functions of independent kinematic variables, the systems of homogeneous linear partial differential equations satisfied by the mentioned scalar integrals are established. Using the calculus of variations, one recognizes the system of linear partial differential equations as stationary conditions of a functional under some given restrictions, which is the cornerstone to perform the continuation of the scalar integrals to whole kinematic domains numerically with the finite element methods. In principle this method can be used to evaluate the scalar integrals of any Feynman diagrams.

   hep-phNPB(2018)·15 citations
7. 07*

   Anomalous leptonic U(1) symmetry: Syndetic origin of the QCD axion, weak-scale dark matter, and radiative neutrino mass

   Ernest Ma🇺🇸 · Diego Restrepo🇨🇴 · Oscar Zapata🇨🇴

   The well-known leptonic U(1) symmetry of the standard model of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a candidate for weak-scale dark matter, as well as radiative neutrino masses. A possible key connection is a color-triplet scalar, which may be produced and detected at the Large Hadron Collider.

   hep-phMod.Phys.Lett.A(2018)·22 citations
8. 08*

   Elastic Hadron Scattering in Various Pomeron Models

   P. Erland🇵🇱 · R. Staszewski🇵🇱 · M. Trzebinski🇵🇱 · R. Kycia🇵🇱

   In this work the process of elastic hadron scattering is discussed. In particular, scattering amplitudes for the various Pomeron models are compared. In addition, differential elastic cross section as a function of the scattered proton transverse momentum for unpolarised and polarised protons is presented. Finally, an implementation of the elastic scattering amplitudes into the GenEx Monte Carlo generator is discussed.

   hep-phActa Phys.Polon.B(2017)·3 citations
9. 09*

   Diphoton production in association with two bottom jets

   Daniel Faeh · Nicolas Greiner🇨🇭

   We study the production of a photon pair in association with two bottom jets at the LHC. This process constitutes an important background to double Higgs production with the subsequent decay of the two Higgs bosons into a pair of photons and b-quarks respectively. We calculate this process at next-to-leading order accuracy in QCD and find that QCD corrections lead to a substantial increase of the production cross section due to new channels opening up at next-to-leading order and their inclusion is therefore inevitable for a reliable prediction. Furthermore, the approximation of massless b-quarks is scrutinized by calculating the process with both massless and massive b-quarks. We find that the massive bottom quark leads to a substantial reduction of the cross section where the biggest effect is however due to the use of a four flavor PDF set and the corresponding smaller values for the strong coupling constant.

   hep-phEPJC(2017)·10 citations
10. 10*

    Stimulated transitions in resonant atom Majorana mixing

    Jose Bernabeu🇪🇸 · Alejandro Segarra🇪🇸

    Massive neutrinos demand to ask whether they are Dirac or Majorana particles. Majorana neutrinos are an irrefutable proof of physics beyond the Standard Model. Neutrinoless double electron capture is not a process but a virtual $\Delta L=2$ mixing between a parent ${}^{A}Z$ atom and a daughter ${}^A(Z-2)$ excited atom with two electron holes. As a mixing between two neutral atoms and the observable signal in terms of emitted two-hole X-rays, the strategy, experimental signature and background are different from neutrinoless double beta decay. The mixing is resonantly enhanced for almost degeneracy and, under these conditions, there is no irreducible background from the standard two-neutrino channel. We reconstruct the natural time history of a nominally stable parent atom since its production either by nature or in the laboratory. After the time periods of atom oscillations and the decay of the short-lived daughter atom, at observable times the relevant "stationary" states are the mixed metastable long-lived state and the non-orthogonal short-lived excited state, as well as the ground state of the daughter atom. We find that they have a natural population inversion which is most appropriate for exploiting the bosonic nature of the observed atomic transitions radiation. Among different observables of the atom Majorana mixing, we include the enhanced rate of stimulated X-ray emission from the long-lived metastable state by a high-intensity X-ray beam: a gain factor of 100 can be envisaged at current XFEL facilities. On the other hand, the historical population of the daughter atom ground state can be probed by exciting it with a current pulsed optical laser, showing the characteristic absorption lines: the whole population can be excited in a shorter time than typical pulse duration.

    hep-phJHEP(2018)·8 citations
11. 11*

    Supernovae and Weinberg's Higgs Portal Dark Radiation and Dark Matter

    Huitzu Tu🇹🇼 · Kin-Wang Ng🇹🇼

    The observed burst duration and energies of the neutrinos from Supernova 1987A strongly limit the possibility of any weakly-interacting light particle species being produced in the proto-neutron star (PNS) core and leading to efficient energy loss. We reexamine this constraint on Weinberg's Higgs portal model, in which the dark radiation particles (the Goldstone bosons) and the dark matter candidate (a Majorana fermion) interact with Standard Model (SM) fields solely through the mixing of the SM Higgs boson and a light Higgs boson. In order for the Goldstone bosons to freely stream out of the PNS core region, the Higgs portal coupling has to be about a factor of $4$--$9$ smaller than the current collider bound inferred from the SM Higgs invisible decay width. We find that in the energy loss rate calculations, results obtained by using the one-pion exchange (OPE) approximation and the SP07 global fits for the nucleon-nucleon total elastic cross section differ only by a factor $\lesssim 3$. The SN 1987A constraints surpass those set by laboratory experiments or by the energy loss arguments in other astrophysical objects such as the gamma-ray bursts, even with other nuclear uncertainties taken into account. Furthermore, the SN 1987A constraints are comparable to bounds from the latest dark matter direct search for low-mass WIMPs ($\lesssim 10\text{Gev}$.)

    hep-phastro-ph.HEJHEP(2017)·18 citations
12. 12*

    Structure Function F_1 singlet in Double-Logarithmic Approximation

    B.I. Ermolaev🇷🇺 · S.I. Troyan🇷🇺

    We calculate the perturbative component of the DIS structure function F_1 singlet in the Double-Logarithmic Approximation (DLA) and account at the same time for the running QCD coupling effects. By constructing and solving evolution equations accounting for the both x- and Q^2- evolutions, we obtain the explicit expression for F_1 and, applying the saddle-point method, calculate its small-x asymptotics which proves to be of the Regge form with the intercept = 1.066. Its large value compensates for the lack of the factor 1/x in the DLA contributions. Such fast growth at small x proves that the DLA expressions are quite important for description of all QCD processes involving the vacuum (Pomeron) exchanges. We also obtain that the small-x asymptotics of F_1 depend on a single variable Q^2/x^2 and show that the small-x asymptotics reliably represent F_1 at x = 10^{-6} or less.

    hep-phhep-ex2 citations
13. 13*

    Phenomenology with F-theory SU(5)

    George K. Leontaris🇬🇷 · Qaisar Shafi🇺🇸

    We explore the low energy phenomenology of an F-theory based SU(5) model which, in addition to the known quarks and leptons, contains Standard Model singlets, and vector-like color triplets and SU(2) doublets. Depending on their masses and couplings, some of these new particles may be observed at the LHC and future colliders. We discuss the restrictions by CKM constraints on their mixing with the ordinary down quarks of the three chiral familes. The model is consistent with gauge coupling unification at the usual supersymmetric GUT scale, dimension five proton decay is adequately suppressed, while dimension-six decay mediated by the superheavy gauge bosons is enhanced by a factor of 5-7. The third generation charged fermion Yukawa couplings yield the corresponding low-energy masses in reasonable agreement with observations. The hierarchical nature of the masses of lighter generations is accounted for via non-renormalisable interactions, with the perturbative vacuum expectation values of the SM singlet fields playing an essential role.

    hep-phhep-thPRD(2017)·10 citations
14. 14*

    A solution to the proton and deuteron size puzzle and the anomalous magnetic moment of the muon

    Jean Paul Mbelek🇨🇲

    We show that a proposal which involves an effective radius derived from an effective potential that includes a linear extra-potential may solve both the proton and deuteron size puzzle. Moreover, this solution preserves the e-{\mu} universality and helps to solve the anomalous magnetic moment of the muon too. Still, it is consistent with the rms magnetic radius of the proton and deuteron, the rms charge radius of both the ordinary and muonic C12 as well as the kaonic and pionic X-rays spectroscopy.

    hep-ph0 citations
15. 15*

    Towards tomography of quark-gluon plasma using double inclusive forward-central jets in Pb-Pb collision

    Michal Deák🇵🇱 · Krzysztof Kutak🇵🇱 · Konrad Tywoniuk🇨🇭

    We propose a new framework, merging High Energy Factorization with final-state jet quenching effects due to interactions in a quark-gluon plasma, to compute di-jet rates at mid- and forward rapidity. It allows to consistently study the interplay of initial-state effects with medium interactions, opening the possibility for understanding the dynamics of hard probes in heavy-ion collisions and the QGP evolution in rapidity.

    hep-phnucl-thEPJC(2017)·4 citations
16. 16*

    Minimal unified resolution to $R_{K^{(\ast )}}$ and $R(D^{(\ast )})$ anomalies with lepton mixing

    Debajyoti Choudhury🇮🇳 · Anirban Kundu🇮🇳 · Rusa Mandal🇮🇳 · Rahul Sinha🇮🇳

    It is a challenging task to explain, in terms of a simple and compelling new physics scenario, the intriguing discrepancies between the standard model expectations and the data for the neutral-current observables $R_K$ and $R_{K^{\ast }}$, as well as the charged-current observables $R(D)$ and $R(D^{\ast })$. We show that this can be achieved in an effective theory with only two unknown parameters. In addition, this class of models predicts some interesting signatures in the context of both $B$ decays as well as high-energy collisions.

    hep-phPRL(2017)·52 citations
17. 17*

    $B$ decay anomalies from nonabelian local horizontal symmetry

    James M. Cline🇨🇦 · Jorge Martin Camalich🇨🇭

    Recent anomalies in $B\to K^{(\ast )}\ell \ell$ meson decays are consistent with exchange of a heavy $Z^{\prime }$ vector boson. Here we try to connect such new physics to understanding the origin of flavor, by gauging generation number. Phenomenological and theoretical considerations suggest that the smallest viable flavor symmetry (not including any extra U(1) factors) is chiral ${\mathrm{SU}(3)}_L\times {\mathrm{SU}(3)}_R$, which acts only on generation indices and does not distinguish between quarks and leptons. Spontaneous breaking of the symmetry gives rise to the standard model Yukawa matrices, and masses for the 16 $Z^{\prime }$-like gauge bosons, one of which is presumed to be light enough to explain the $B\to K^{(\ast )}\ell \ell$ anomalies. We perform a bottom-up study of this framework, showing that it is highly constrained by LHC dilepton searches, meson mixing, $Z$ decays and CKM unitarity. Similar anomalies are predicted for semileptonic decays of $B$ to lighter mesons, with excesses in the $ee,\tau \tau$ channels and deficits in $\mu \mu$, but no deviation in $\nu \nu$. The lightest $Z^{\prime }$ mass is $\lesssim 6$TeV if the gauge coupling is $\lesssim 1$.

    hep-phPRD(2017)·28 citations
18. 18*

    Correlating Lepton Flavour (Universality) Violation in $B$ Decays with $\mu \to e\gamma$ using Leptoquarks

    Andreas Crivellin🇨🇭 · Dario Mueller🇨🇭 · Adrian Signer🇨🇭 · Yannick Ulrich🇨🇭

    Motivated by the measurements of $b\to s{\ell }^{+}{\ell }^{-}$ transitions, including $R(K)$ and $R(K^{\ast })$, we examine lepton flavour (universality) violation in $B$ decays and its connections to $\mu \to e\gamma$ in generic leptoquark models. Considering all 10 representations of scalar and vector leptoquarks under the Standard Model gauge group we compute the tree-level matching for semileptonic $b$-quark operators as well as their loop effects in $\ell \to {\ell }^{\prime }\gamma$. In our phenomenological analysis we correlate $R(K)$, $R(K^{\ast })$ and the other $b\to s{\mu }^{+}{\mu }^{-}$ data to $\mu \to e\gamma$ and $b\to s\mu e$ transitions for the three leptoquark representations that generate left-handed currents in $b\to s{\ell }^{+}{\ell }^{-}$ transitions and, therefore, provide a good fit to data. We find that while new physics contributions to muons are required by the global fit, also couplings to electrons can be sizeable without violating the stringent bounds from $\mu \to e\gamma$. In fact, if the effect in electrons in $b\to s{\ell }^{+}{\ell }^{-}$ has opposite sign than the effect in muons the bound from $\mu \to e\gamma$ can always be avoided. However, unavoidable effects in $b\to s\mu e$ transitions (i.e. $B_s\to \mu e$, $B\to K\mu e$, etc.) appear which are within the reach of LHCb and BELLE II.

    hep-phhep-exPRD(2018)·75 citations
19. 19*

    Pure Natural Inflation

    Yasunori Nomura🇺🇸 · Taizan Watari🇯🇵 · Masahito Yamazaki🇯🇵

    We point out that a simple inflationary model in which the axionic inflaton couples to a pure Yang-Mills theory may give the scalar spectral index (n_s) and tensor-to-scalar ratio (r) in complete agreement with the current observational data.

    hep-phastro-ph.COhep-thPLB(2018)·48 citations
20. 20*

    From the trees to the forest: a review of radiative neutrino mass models

    Yi Cai🇦🇺 · Juan Herrero-García🇦🇺 · Michael A. Schmidt🇦🇺 · Avelino Vicente🇪🇸 · Raymond R. Volkas🇦🇺

    A plausible explanation for the lightness of neutrino masses is that neutrinos are massless at tree level, with their mass (typically Majorana) being generated radiatively at one or more loops. The new couplings, together with the suppression coming from the loop factors, imply that the new degrees of freedom cannot be too heavy (they are typically at the TeV scale). Therefore, in these models there are no large mass hierarchies and they can be tested using different searches, making their detailed phenomenological study very appealing. In particular, the new particles can be searched for at colliders and generically induce signals in lepton-flavor and lepton-number violating processes (in the case of Majorana neutrinos), which are not independent from reproducing correctly the neutrino masses and mixings. The main focus of the review is on Majorana neutrinos. We order the allowed theory space from three different perspectives: (i) using an effective operator approach to lepton number violation, (ii) by the number of loops at which the Weinberg operator is generated, (iii) within a given loop order, by the possible irreducible topologies. We also discuss in more detail some popular radiative models which involve qualitatively different features, revisiting their most important phenomenological implications. Finally, we list some promising avenues to pursue.

    hep-phFront.in Phys.(2017)·430 citations
21. 21*

    On the Light Massive Flavor Dependence of the Large Order Asymptotic Behavior and the Ambiguity of the Pole Mass

    Andre H. Hoang🇦🇹 · Christopher Lepenik🇦🇹 · Moritz Preisser🇦🇹

    We provide a systematic renormalization group formalism for the mass effects in the relation of the pole mass $m_Q^{\mathrm{pole}}$ and short-distance masses such as the $\overline{\mathrm{MS}}$ mass ${\overline{m}}_Q$ of a heavy quark $Q$, coming from virtual loop insertions of massive quarks lighter than $Q$. The formalism reflects the constraints from heavy quark symmetry and entails a combined matching and evolution procedure that allows to disentangle and successively integrate out the corrections coming from the lighter massive quarks and the momentum regions between them and to precisely control the large order asymptotic behavior. With the formalism we systematically sum logarithms of ratios of the lighter quark masses and $m_Q$, relate the QCD corrections for different external heavy quarks to each other, predict the $\mathcal{O}({\alpha }_s^4)$ virtual quark mass corrections in the pole-$\overline{\mathrm{MS}}$ mass relation, calculate the pole mass differences for the top, bottom and charm quarks with a precision of around $20$ MeV and analyze the decoupling of the lighter massive quark flavors at large orders. The summation of logarithms is most relevant for the top quark pole mass $m_t^{\mathrm{pole}}$, where the hierarchy to the bottom and charm quarks is large. We determine the ambiguity of the pole mass for top, bottom and charm quarks in different scenarios with massive or massless bottom and charm quarks in a way consistent with heavy quark symmetry, and we find that it is $250$ MeV. The ambiguity is larger than current projections for the precision of top quark mass measurements in the high-luminosity phase of the LHC.

    hep-phJHEP(2017)·80 citations
22. 22*

    CP-violation for Electroweak Baryogenesis from Dynamical CKM Matrix

    Sebastian Bruggisser🇩🇪 · Thomas Konstandin🇩🇪 · Geraldine Servant🇩🇪

    We show that the CKM matrix can be the source of CP violation for electroweak baryogenesis if Yukawa couplings vary at the same time as the Higgs acquires its vacuum expectation value. This offers new avenues for explaining the baryon asymmetry of the universe. These ideas apply if the mechanism explaining the flavour structure of the Standard Model is connected to electroweak symmetry breaking. We compute the resulting baryon asymmetry for various low-scale flavour models and different configurations of the Yukawa coupling variation across the bubble wall, and show that it can naturally be of the right order.

    hep-phJCAP(2017)·47 citations
23. 23*

    SU(5) Unification without Proton Decay

    Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸

    We construct a four-dimensional SU(5) grand unified theory in which the proton is stable. The Standard Model leptons reside in the 5 and 10 irreps of SU(5), whereas the quarks live in the 40 and 50 irreps. The SU(5) gauge symmetry is broken by the vacuum expectation values of the scalar 24 and 75 irreps. All non-Standard Model fields are heavy. Stability of the proton requires three relations between the parameters of the model to hold. However, abandoning the requirement of absolute proton stability, the model fulfills current experimental constraints without fine-tuning.

    hep-phhep-thPRL(2017)·20 citations
24. 24*

    The Not-So-Well Tempered Neutralino

    Stefano Profumo🇺🇸 · Tim Stefaniak🇺🇸 · Laurel Stephenson Haskins🇺🇸

    Light electroweakinos, the neutral and charged fermionic supersymmetric partners of the Standard Model $\mathrm{SU}(2)\times \mathrm{U}(1)$ gauge bosons and of the two $\mathrm{SU}(2)$ Higgs doublets, are an important target for searches for new physics with the Large Hadron Collider (LHC). However, if the lightest neutralino is the dark matter, constraints from direct dark matter detection experiments rule out large swaths of the parameter space accessible to the LHC, including in large part the so-called "well-tempered" neutralinos. We focus on the Minimal Supersymmetric Standard Model (MSSM) and explore in detail which regions of parameter space are not excluded by null results from direct dark matter detection, assuming exclusive thermal production of neutralinos in the early universe, and illustrate the complementarity with current and future LHC searches for electroweak gauginos. We consider both bino-Higgsino and bino-wino "not-so-well-tempered" neutralinos, i.e. we include models where the lightest neutralino constitutes only part of the cosmological dark matter, with the consequent suppression of the constraints from direct and indirect dark matter searches.

    hep-phPRD(2017)·42 citations
25. 25*

    A note on a covariant version of Verlinde's emergent gravity

    De-Chang Dai🇨🇳 · Dejan Stojkovic🇺🇸

    Following recent Verlinde's heuristic construction or emergent gravity, Hossenfelder wrote down the Lagrangian capturing some aspects of this theory. We point out that there is an error in calculations whose consequence is that a cosmological de Sitter space solution is not recovered from this Lagrangian. We correct this error in order to obtain the desired solution. We also show that small perturbations around de Sitter space grow, which implies that this state is not stable. However, the presence of matter and radiation might in principle provide stability.

    ↳ gr-qchep-phhep-thPRD(2017)·22 citations
26. 26*

    Attractor Models in Scalar-Tensor Theories of Inflation

    Sukannya Bhattacharya🇮🇳 · Kumar Das🇮🇳 · Koushik Dutta🇮🇳

    In this work we study the cosmological attractor models of inflation in connection with certain scalar-tensor theories of gravity, e.g $f(R)$ gravity and Brans-Dicke theory. For some particular choices of the functional degrees of freedom in these theories, one obtains Starobinsky like predictions in the ($n_s$-$r$) observable plane. We have demonstrated that these choices in the Lagrangian density of certain $f(R)$ and Brans-Dicke theories fulfil the condition of the cosmological attractors. That explains why known predictions of $f(R)$ and Brans-Dicke theories in certain cases appear to be the predictions of the much discussed attractor theories. In addition, we did an analysis showing how the predictions of an attractor model is preserved with respect to the variation in the functional freedom of the theory.

    ↳ gr-qcastro-ph.COhep-phhep-thInt.J.Mod.Phys.D(2018)·11 citations
27. 27*

    EFT of Inflation: Reflections on CMB and Forecasts on LSS Surveys

    Abhishek Naskar🇮🇳 · Sayantan Choudhury🇮🇳 · Argha Banerjee🇺🇸 · Supratik Pal🇮🇳

    We investigate the possibility of constraining parameters of Effective Field Theory (EFT) of inflation with upcoming Large Scale Structure (LSS) surveys in order to have a better understanding of inflationary dynamics. With the development of the construction algorithm of EFT, we arrive at a properly truncated action for the entire scenario. Using this, we compute the two-point correlation function for quantum fluctuations from Goldstone modes and related inflationary observables in terms of coefficients of relevant EFT operators. We then perform Fisher matrix forecast analysis to estimate the possible error bars on the parameters of EFT as well as on the inflationary parameters using two upcoming LSS surveys, namely, LSST and EUCLID.

    ↳ astro-ph.COgr-qchep-phhep-th26 citations
28. 28*

    A Semiclassical, Entropic Proof of a Weak Gravity Conjecture

    Zachary Fisher🇺🇸 · Christopher J. Mogni🇺🇸

    We present a semiclassical proof of the weak gravity conjecture in $D=4$ spacetime dimensions for scalar matter gauged under a $U(1{)}^N$ gauge group. We compute the non-perturbative macroscopic entropy of a scalar field in an extremal black hole background at the level of linearized backreaction on the metric. The scalar field is assumed to violate or saturate the weak gravity conjecture. The scalar contributes a logarithmic correction to the entropy in the black hole geometry that outgrows the classical contribution. We demonstrate that the entropy of the gauged scalar violates the generalized second law in the limit of large black hole charge. Our result suggests that entropy inequalities may directly discriminate between effective field theories that live in the landscape versus the swampland.

    ↳ hep-thhep-ph29 citations
29. 29*

    Formation of exotic baryon clusters in ultra-relativistic heavy-ion collisions

    A.S.Botvina (Frankfurt U., FIAS, ITP & Moscow, INR)🇩🇪 · J.Steinheimer (Frankfurt U., FIAS)🇩🇪 · M.Bleicher (Frankfurt U., FIAS, ITP & Juelich FZJ, NIC, JSC)🇩🇪

    Recent experiments at RHIC and LHC have demonstrated that there are excellent opportunities to produce light baryonic clusters of exotic matter (strange and anti-matter) in ultra-relativistic ion collisions. Within the hybrid-transport model UrQMD we show that the coalescence mechanism can naturally explain the production of these clusters in the ALICE experiment at LHC. As a consequence of this mechanism we predict the rapidity domains where the yields of such clusters are much larger than the observed one at midrapidity. This new phenomenon can lead to unique methods for producing exotic nuclei.

    ↳ nucl-thhep-phnucl-exPRC(2017)·18 citations
30. 30*

    Edge states and thermodynamics of rotating relativistic fermions under magnetic field

    M. N. Chernodub🇫🇷 · Shinya Gongyo🇯🇵

    We discuss free Dirac fermions rotating uniformly inside a cylindrical cavity in the presence of background magnetic field parallel to the cylinder axis. We show that in addition to the known bulk states the system contains massive edge states with the masses inversely proportional to the radius of the cylinder. The edge states appear at quantized threshold values of the fermion mass. In the limit of infinite fermion mass the masses of the edge states remain finite but, generally, nonzero as contrasted to the bulk states whose masses become infinite. The presence of magnetic field affects the spectrum of both bulk and edge modes, and the masses of the edge states may vanish at certain values of magnetic field. The moment of inertia of Dirac fermions is non-monotonically increasing, oscillating function of magnetic field. The oscillations are well pronounced in a low-temperature domain and they disappear at high temperatures.

    ↳ hep-thcond-mat.othercond-mat.quant-gashep-phPRD(2017)·40 citations
31. 31*

    Operator bases, $S$-matrices, and their partition functions

    Brian Henning🇺🇸 · Xiaochuan Lu🇺🇸 · Tom Melia🇺🇸 · Hitoshi Murayama🇺🇸

    Relativistic quantum systems that admit scattering experiments are quantitatively described by effective field theories, where $S$-matrix kinematics and symmetry considerations are encoded in the operator spectrum of the EFT. In this paper we use the $S$-matrix to derive the structure of the EFT operator basis, providing complementary descriptions in (i) position space utilizing the conformal algebra and cohomology and (ii) momentum space via an algebraic formulation in terms of a ring of momenta with kinematics implemented as an ideal. These frameworks systematically handle redundancies associated with equations of motion (on-shell) and integration by parts (momentum conservation). We introduce a partition function, termed the Hilbert series, to enumerate the operator basis--correspondingly, the $S$-matrix--and derive a matrix integral expression to compute the Hilbert series. The expression is general, easily applied in any spacetime dimension, with arbitrary field content and (linearly realized) symmetries. In addition to counting, we discuss construction of the basis. Simple algorithms follow from the algebraic formulation in momentum space. We explicitly compute the basis for operators involving up to $n=5$ scalar fields. This construction universally applies to fields with spin, since the operator basis for scalars encodes the momentum dependence of $n$-point amplitudes. We discuss in detail the operator basis for non-linearly realized symmetries. In the presence of massless particles, there is freedom to impose additional structure on the $S$-matrix in the form of soft limits. The most naïve implementation for massless scalars leads to the operator basis for pions, which we confirm using the standard CCWZ formulation for non-linear realizations.

    ↳ hep-thhep-phJHEP(2017)·195 citations
32. 32*

    Was the Universe Actually Radiation Dominated Prior to Nucleosynthesis?

    John T. Giblin · Jr. · Gordon Kane · Eva Nesbit · Scott Watson · Yue Zhao

    Maybe not. String theory approaches to both beyond the Standard Model and Inflationary model building generically predict the existence of scalars (moduli) that are light compared to the scale of quantum gravity. These moduli become displaced from their low energy minima in the early universe and lead to a prolonged matter-dominated epoch prior to BBN. In this paper, we examine whether non-perturbative effects such as parametric resonance or tachyonic instabilities can shorten, or even eliminate, the moduli condensate and matter-dominated epoch. Such effects depend crucially on the strength of the couplings, and we find that unless the moduli become strongly coupled the matter-dominated epoch is unavoidable. In particular, we find that in string and M-theory compactifications where the lightest moduli are near the TeV-scale that a matter-dominated epoch will persist until the time of Big Bang Nucleosynthesis.

    ↳ hep-thastro-ph.COhep-phPRD(2017)·36 citations
33. 33*

    Nature of chiral phase transition in two-flavor QCD

    K.-I. Ishikawa🇯🇵 · Y. Iwasaki🇯🇵 · Yu Nakayama🇯🇵 · T. Yoshie🇯🇵

    We investigate the nature of the chiral phase transition in the massless two-flavor QCD using the renormalization group improved gauge action and the Wilson quark action on $32^3\times 16$, $24^3\times 12$, and $16^3\times 8$ lattices. We calculate the spacial and temporal propagators of the iso-triplet mesons in the pseudo-scalar ($PS$), scalar ($S$), vector ($V$) and axial-vector ($AV$) channels on the lattice of three sizes. We first verify that the RG scaling is excellently satisfied for all cases. This is consistent with the claim that the chiral phase transition is second order. Then we compare the spacial and temporal effective masses between the axial partners, i.e. $PS$ vs $S$ and $V$ vs $AV$, on each of the three size lattices. We find the effective masses of all of six cases for the axial partners agree remarkably. This is consistent with the claim that at least $Z_4$ subgroup of the $U_A(1)$ symmetry in addition to the $S{U}_A(2)$ symmetry is recovered at the chiral phase transition point.

    ↳ hep-lathep-phhep-th11 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.