Mon·Jul 11, 2016Monday·July 11, 2016

1. 01*

   Integrating out heavy particles with functional methods: a simplified framework

   Javier Fuentes-Martin🇪🇸 · Jorge Portoles🇪🇸 · Pedro Ruiz-Femenia🇩🇪

   We present a systematic procedure to obtain the one-loop low-energy effective Lagrangian resulting from integrating out the heavy fields of a given ultraviolet theory. We show that the matching coefficients are determined entirely by the hard region of the functional determinant involving the heavy fields. This represents an important simplification with respect the conventional matching approach, where the full and effective theory contributions have to be computed separately and a cancellation of the infrared divergent parts has to take place. We illustrate the method with a descriptive toy model and with an extension of the Standard Model with a heavy real scalar triplet. A comparison with other schemes that have been put forward recently is also provided.

   hep-phhep-thJHEP(2016)·140 citations
2. 02*

   Capabilities of long-baseline experiments in the presence of a sterile neutrino

   Debajyoti Dutta🇮🇳 · Raj Gandhi🇮🇳 · Boris Kayser🇺🇸 · Mehedi Masud🇮🇳 · Suprabh Prakash🇮🇳

   Assuming that there is a sterile neutrino, we ask what then is the ability of long-baseline experiments to i) establish that neutrino oscillation violates CP, ii) determine the three-neutrino mass ordering, and iii) determine which CP-violating phase or phases are the cause of any CP violation that may be observed. We find that the ability to establish CP violation and to determine the mass ordering could be very substantial. However, the effects of the sterile neutrino could be quite large, and it might prove very difficult to determine which phase is responsible for an observed CP violation. We explain why a sterile neutrino changes the long-baseline sensitivities to CP violation and to the mass ordering in the ways that it does. We note that long-baseline experiments can probe the presence of sterile neutrinos in a way that is different from, and complementary to, the probes of short-baseline experiments. We explore the question of how large sterile-active mixing angles need to be before long-baseline experiments can detect their effects, or how small they need to be before the interpretation of these experiments can safely disregard the possible existence of sterile neutrinos.

   hep-phhep-exJHEP(2016)·59 citations
3. 03*

   Small-$x$ resummation from HELL

   Marco Bonvini🇬🇧 · Simone Marzani🇺🇸 · Tiziano Peraro🇬🇧

   Small-$x$ logarithmic enhancements arising from high-energy gluon emissions affect both the evolution of collinearly-factorized parton densities and partonic coefficient functions. With the higher collider energy reached by the LHC, the prospect of a future high-energy collider, and the recent deep-inelastic scattering (DIS) results at small-$x$ from HERA, providing phenomenological tools for performing small-$x$ resummation has become of great relevance. In this paper we discuss a framework to perform small-$x$ resummation for both parton evolution and partonic coefficient functions and we describe its implementation in a computer code named High-Energy Large Logarithms (HELL). We present resummed and matched results for the DGLAP splitting functions and, as a proof of principle, for the massless structure functions in DIS.

   hep-phEPJC(2016)·76 citations
4. 04*

   Degenerate Higgs bosons: hiding a second Higgs at 125 GeV

   Ning Chen🇨🇳 · Zuowei Liu🇨🇳

   More than one Higgs boson may be present near the currently discovered Higgs mass, which can not be properly resolved due to the limitations in the intrinsic energy resolution at the Large Hadron Collider. We investigated the scenarios where two $CP$-even Higgs bosons are degenerate in mass. To correctly predict the Higgs signatures, quantum interference effects between the two Higgs bosons must be taken into account, which, however, has been often neglected in the literature. We carried out a global analysis including the interference effects for a variety of Higgs searching channels at the Large Hadron Collider, which suggests that the existence of two degenerate Higgs bosons near 125 GeV is highly likely. Prospects of distinguishing the degenerate Higgs case from the single Higgs case are discussed.

   hep-phhep-ex3 citations
5. 05*

   The Dilaton-like Higgs boson with scalar singlet dark matter

   Robyn Campbell🇨🇦 · Stephen Godfrey🇨🇦 · Alejandro de la Puente🇨🇦

   We study a model with a Higgs-like dilaton and a Standard Model gauge-singlet scalar dark matter candidate. We begin by updating the status of identifying the observed 125 GeV Higgs-like boson with the pseudo Nambu-Goldstone boson that arises from the spontaneous breaking of scale invariance using recent Higgs boson signal strength measurements by the ATLAS and CMS collaborations. We then constrain the extended model with recent constraints on the Higgs invisible width, the observed dark matter relic abundance and the latest dark matter direct detection limits. We found that the magnitude of the dilaton-$\gamma \gamma$ and dilaton-glue-glue coupling is constrained to be close to the standard model values. The mass of the dark matter candidate is contrained to be greater than half the dilaton mass by relic abundance limits and Higgs invisible width limits. Dark matter direct detection limits allow only small mass regions which will be further constrained by upcoming DEAP measurements.

   hep-phPRD(2016)·1 citation
6. 06*

   Nonthermal Fixed Points in Quantum Field Theory Beyond the Weak-Coupling Limit

   Jürgen Berges🇩🇪 · Benjamin Wallisch🇬🇧

   Quantum systems in extreme conditions can exhibit universal behavior far from equilibrium associated to nonthermal fixed points with a wide range of topical applications from early-universe inflaton dynamics and heavy-ion collisions to strong quenches in ultracold quantum gases. So far, most studies have relied on a mapping of the quantum dynamics onto a classical-statistical theory that can be simulated on a computer. However, the mapping is based on a weak-coupling limit, while phenomenological applications often require moderate interaction strengths. We report on the observation of nonthermal fixed points directly in quantum field theory beyond the weak-coupling limit. For the example of a relativistic scalar O(N)-symmetric quantum field theory, we numerically solve the nonequilibrium dynamics employing a 1/N expansion to next-to-leading order, which does not rely on a small coupling parameter. Starting from two different sets of overoccupied and of strong-field initial conditions, we find that nonthermal fixed points are not restricted to parameter ranges suitable for classical-statistical simulations, but extend also to couplings of order one. While the infrared behavior is found to be insensitive to the differences in the initial conditions, we demonstrate that transport phenomena to higher momenta depend on the presence or absence of a symmetry-breaking field expectation value.

   hep-phhep-thnucl-thPRD(2017)·43 citations
7. 07*

   $B$ and $B_s$ Meson Spectroscopy

   Stephen Godfrey (Carleton)🇨🇦 · Kenneth Moats (Carleton)🇨🇦 · Eric S. Swanson (Pittsburgh)🇺🇸

   Properties of bottom and bottom-strange mesons are computed in two relativized quark models. Model masses and wavefunctions are used to predict radiative transition rates and the ${}^3{P}_0$ quark pair creation model is used to compute strong decay widths. A comparison to recently observed bottom and bottom-strange states is made. We find that there are numerous excited $B$ and $B_s$ mesons that have relatively narrow widths and significant branching ratios to simple final states such as $B\pi$, $B^{\ast }\pi$, $BK$, and $B^{\ast }K$ that could be observed in the near future.

   hep-phhep-exPRD(2016)·121 citations
8. 08*

   Signals of Two Universal Extra Dimensions at the LHC

   G. Burdman🇧🇷 · O. J. P. Eboli🇧🇷 · D. Spehler🇫🇷

   Extensions of the standard model with universal extra dimensions are interesting both as phenomenological templates as well as model-building fertile ground. For instance, they are one the prototypes for theories exhibiting compressed spectra, leading to difficult searches at the LHC since the decay products of new states are soft and immersed in a large standard model background. Here we study the phenomenology at the LHC of theories with two universal extra dimensions. We obtain the current bound by using the production of second level excitations of electroweak gauge bosons decaying to a pair of leptons and study the reach of the LHC Run~II in this channel. We also introduce a new channel originating in higher dimensional operators and resulting in the single production of a second level quark excitation. Its subsequent decay into a hard jet and lepton pair resonance would allow the identification of a more model-specific process, unlike the more generic vector resonance signal. We show that the sensitivity of this channel to the compactification scale is very similar to the one obtained using the vector resonance.

   hep-phhep-exPRD(2016)·11 citations
9. 09*

   Exclusive meson production at HERMES

   Sergey Manaenkov (on behalf of the HERMES collaboration)🇷🇺

   The data were accumulated with the HERMES forward spectrometer using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. Exclusive electroproduction of $\omega$ mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of $Q^2>1.0$ GeV${}^2$, 3.0 GeV $<W<$ 6.3 GeV, and $-t^{\prime }<0.2$ GeV${}^2$, while for ${\rho }^0$-meson production on a transversely polarized hydrogen target $-t^{\prime }<0.4$ GeV${}^2$ is used. Spin-density matrix elements for $\omega$ production are presented in projections of $Q^2$ or $-t^{\prime }$, while the ratios of the helicity amplitudes for the reaction ${\gamma }^{\ast }+p\to {\rho }^0+p$ are obtained in the entire kinematic region. The usage of the transversely polarized target allows for the first time the extraction of the ratios of certain nucleon-helicity-flip amplitudes to the natural-parity exchange amplitude $T_{0\frac{1}{2}0\frac{1}{2}}$ without the nucleon-helicity flip describing the longitudinal ${\rho }^0$-meson production by the longitudinal virtual photon. Violation of $s$-channel helicity conservation is observed for both mesons. A dominant contribution from unnatural-parity exchange (UPE) is established for special combinations of the $\omega$ spin-density matrix elements. For ${\rho }^0$-meson production, the UPE amplitude without the nucleon-helicity flip, $U_{1\frac{1}{2}1\frac{1}{2}}$, is shown to be the largest UPE amplitude. Good agreement is found between the HERMES data on $\omega$ production on the proton and results of the perturbative QCD-inspired Goloskokov-Kroll model that includes pion-pole contribution.

   hep-phPoS(2016)·1 citation
10. 10*

    Momentum broadening in unstable quark-gluon plasma

    M.E. Carrington🇨🇦 · St. Mrówczyński🇵🇱 · B. Schenke🇺🇸

    Quark-gluon plasma produced at the early stage of ultrarelativistic heavy ion collisions is unstable, if weakly coupled, due to the anisotropy of its momentum distribution. Chromomagnetic fields are spontaneously generated and can reach magnitudes much exceeding typical values of the fields in equilibrated plasma. We consider a high energy test parton traversing an unstable plasma that is populated with strong fields. We study the momentum broadening parameter $\hat{q}$ which determines the radiative energy loss of the test parton. We develop a formalism which gives $\hat{q}$ as the solution of an initial value problem, and we focus on extremely oblate plasmas which are physically relevant for relativistic heavy ion collisions. The parameter $\hat{q}$ is found to be strongly dependent on time. For short times it is of the order of the equilibrium value, but at later times $\hat{q}$ grows exponentially due to the interaction of the test parton with unstable modes and becomes much bigger than the value in equilibrium. The momentum broadening is also strongly directionally dependent and is largest when the test parton velocity is transverse to the beam axis. Consequences of our findings for the phenomenology of jet quenching in relativistic heavy ion collisions are briefly discussed.

    hep-phhep-thnucl-thPRC(2017)·31 citations
11. 11*

    Sterile Neutrino portal to Dark Matter II: Exact Dark symmetry

    Miguel Escudero🇪🇸 · Nuria Rius🇪🇸 · Verónica Sanz🇬🇧

    We analyze a simple extension of the Standard Model (SM) with a dark sector composed of a scalar and a fermion, both singlets under the SM gauge group but charged under a dark sector symmetry group. Sterile neutrinos, which are singlets under both groups, mediate the interactions between the dark sector and the SM particles, and generate masses for the active neutrinos via the seesaw mechanism. We explore the parameter space region where the observed Dark Matter relic abundance is determined by the annihilation into sterile neutrinos, both for fermion and scalar Dark Matter particles. The scalar Dark Matter case provides an interesting alternative to the usual Higgs portal scenario. We also study the constraints from direct Dark Matter searches and the prospects for indirect detection via sterile neutrino decays to leptons, which may be able to rule out Dark Matter masses below and around 100 GeV.

    hep-phastro-ph.COEPJC(2017)·111 citations
12. 12*

    Bosonic Decays of Charged Higgs Bosons in a 2HDM Type-I

    Abdesslam Arhrib🇲🇦 · Rachid Benbrik🇲🇦 · Stefano Moretti🇬🇧

    In this study, we focus on the bosonic decays of light charged Higgs bosons in the 2-Higgs Doublet Model (2HDM) Type-I. We quantify the Branching Ratios (BRs) of the $H^{\pm }\to W^{\pm }h$ and $H^{\pm }\to W^{\pm }A$ channels and show that they could be substantial over several areas of the parameter space of the 2HDM Type-I that are still allowed by Large Hadron Collider (LHC) and other experimental data as well as theoretical constraints. We suggest that $H^{\pm }\to W^{\pm }h$ and/or $H^{\pm }\to W^{\pm }A$ could be used as a feasible discovery channel alternative to $H^{\pm }\to \tau \nu$.

    hep-phhep-exEPJC(2017)·66 citations
13. 13*

    Interpretation of Axial Resonances in J/psi-phi at LHCb

    L. Maiani🇮🇹 · A.D. Polosa🇮🇹 · V. Riquer🇮🇹

    We suggest that the J/psi phi structures observed by LHCb can be fitted in two tetraquak multiplets, the S-wave ground state and the first radial excitation, with composition [cs][cbar sbar]. When compared to the previously identified [cq][cbar qbar] multiplet, the observed masses agree with what expected for a multiplet with q -->s. We propose the X(4274), fitted by LHCb with a single 1^++ resonance, to correspond rather to two, almost degenerate, unresolved lines with J^PC = 0^++, 2^++. Masses of missing particles in the 1S and 2S multiplets are predicted.

    hep-phPRD(2016)·64 citations
14. 14*

    Janus-Facedness of the Pion: Analytic Instantaneous Bethe-Salpeter Models

    Wolfgang Lucha🇦🇹

    Inversion enables the construction of interaction potentials underlying - under fortunate circumstances even analytic - instantaneous Bethe-Salpeter descriptions of all lightest pseudoscalar mesons as quark-antiquark bound states of Goldstone-boson nature.

    hep-phnucl-thEPJ Web Conf.(2016)·5 citations
15. 15*

    Assessing Compatibility of Direct Detection Data: Halo-Independent Global Likelihood Analyses

    Graciela B. Gelmini🇺🇸 · Ji-Haeng Huh🇨🇭 · Samuel J. Witte🇺🇸

    We present two different halo-independent methods to assess the compatibility of several direct dark matter detection data sets for a given dark matter model using a global likelihood consisting of at least one extended likelihood and an arbitrary number of Gaussian or Poisson likelihoods. In the first method we find the global best fit halo function (we prove that it is a unique piecewise constant function with a number of down steps smaller than or equal to a maximum number that we compute) and construct a two-sided pointwise confidence band at any desired confidence level, which can then be compared with those derived from the extended likelihood alone to assess the joint compatibility of the data. In the second method we define a "constrained parameter goodness-of-fit" test statistic, whose $p$-value we then use to define a "plausibility region" (e.g. where $p\ge 10\%$). For any halo function not entirely contained within the plausibility region, the level of compatibility of the data is very low (e.g. $p<10\%$). We illustrate these methods by applying them to CDMS-II-Si and SuperCDMS data, assuming dark matter particles with elastic spin-independent isospin-conserving interactions or exothermic spin-independent isospin-violating interactions.

    hep-phastro-ph.COJCAP(2016)·32 citations
16. 16*

    Modelling Inflation with a Power-law Approach to the Inflationary Plateau

    Konstantinos Dimopoulos🇬🇧 · Charlotte Owen🇬🇧

    A new family of inflationary models is introduced and analysed. The behaviour of the parameters characterising the models suggest preferred values, which generate the most interesting testable predictions. Results are further improved if late reheating and/or a subsequent period of thermal inflation is taken into account. Specific model realisations consider a sub-Planckian inflaton variation or a potential without fine-tuning of mass scales, based on the Planck and grand unified theory scales. A toy model realisation in the context of global and local supersymmetry is examined and results fitting the Planck observations are determined.

    hep-phastro-ph.HEhep-thPRD(2016)·22 citations
17. 17*

    Entanglement of Vacuum States With the de Sitter Horizon: Consequences on Holographic Dark Energy

    Rafael Pavão🇪🇸 · Ricardo Faleiro🇵🇹 · Alex H. Blin🇵🇹 · Brigitte Hiller🇵🇹

    The aim of this article is to study the effect of an Event Horizon on the entanglement of the Quantum Vacuum and how entanglement, together with the Holographic Principle, may explain the current value of the Cosmological Constant, in light of recent theories. Entanglement is tested for vacuum states very near and very far from the Horizon of a de Sitter Universe, using the Peres-Horodecki (PPT) criterion. A scalar vacuum field ($\hat{\varphi }$) is averaged inside two boxes of volume $V$ in different spatial positions such that it acquires the structure of a bipartite Quantum Harmonic Oscillator, for which the PPT criterion is a necessary but not sufficient condition of separability. Entanglement is found between states obtained from boxes shaped as spherical shells with thickness of the order of one Planck distance ($l_p$), when one of the states is near the Horizon, and the other state is anywhere in the Universe. Entanglement disappears when the distance of the state near the horizon and the Horizon increases to around $5l_p$. If we consider the Horizon not as a surface but as a spherical shell of thickness $l_p$, then this means that there is entanglement between the states in the Horizon and the rest of the Universe. When both states are at distances larger than $\sim 5l_p$ from the Horizon, no entanglement is found.

    ↳ gr-qchep-phquant-ph2 citations
18. 18*

    Cosmological constraints on dark matter annihilation and decay: Cross-correlation analysis of the extragalactic $\gamma$-ray background and cosmic shear

    Masato Shirasaki🇯🇵 · Oscar Macias🇺🇸 · Shunsaku Horiuchi🇺🇸 · Satoshi Shirai🇩🇪 · Naoki Yoshida🇯🇵

    We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of $\sim 660$ squared degrees in total. We improve upon our previous analyses by using an updated extragalactic $\gamma$-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological $N$-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of $\sim 100$ in the mass range of O(1) TeV when including contributions from secondary $\gamma$ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of $⟨\sigma v⟩\sim 10^{-23}{\mathrm{cm}}^3/\mathrm{s}$ are excluded for TeV-scale DM depending on channel. Lifetimes of $\sim 10^{25}$ sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.

    ↳ astro-ph.COhep-phPRD(2016)·39 citations
19. 19*

    Production of light nuclei in the thermal and coalescence models

    Stanislaw Mrowczynski🇵🇱

    The thermal model properly describes the production yields of light nuclei in relativistic heavy-ion collisions even so the loosely bound sizable nuclei cannot exist in the dense and hot hadron gas at a chemical freeze-out. Within the coalescence model, light nuclei are formed at the latest stage of nuclear collisions - a kinetic freeze-out - due to final state interactions. After discussing the models, we derive simple analytic formulas and, using model parameters directly inferred from experimental data, we show that the thermal and coalescence model predictions are quantitatively close to each other. A possibility to falsify one of the two models is suggested.

    ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2017)·74 citations
20. 20*

    Wilson lines, Grassmannians and Gauge Invariant Off-shell Amplitudes in N=4 SYM

    L.V. Bork🇷🇺 · A.I. Onishchenko🇷🇺

    In this paper we consider tree-level gauge invariant off-shell amplitudes (Wilson line form factors) in $\mathcal{N}=4$ SYM. For the off-shell amplitudes with one leg off-shell we present a conjecture for their Grassmannian integral representation in spinor helicity, twistor and momentum twistor parameterizations. The presented conjecture is successfully checked against BCFW results for MHV${}_n$, NMHV${}_4$ and NMHV${}_5$ off-shell amplitudes. We have also verified that our Grassmannian integral representation correctly reproduces soft (on-shell) limit for the off-shell gluon momentum. It is shown that the (deformed) off-shell amplitude expressions could be also obtained using quantum inverse scattering method for auxiliary $gl(4|4)$ super spin chain.

    ↳ hep-thhep-phJHEP(2017)·27 citations
21. 21*

    Post-Newtonian parameter $\gamma$ for multiscalar-tensor gravity with a general potential

    Manuel Hohmann🇪🇪 · Laur Jarv🇪🇪 · Piret Kuusk🇪🇪 · Erik Randla🇪🇪 · Ott Vilson🇪🇪

    We compute the parametrized post-Newtonian parameter $\gamma$ in the case of a static point source for multiscalar-tensor gravity with completely general nonderivative couplings and potential in the Jordan frame. Similarly to the single massive field case $\gamma$ depends exponentially on the distance from the source and is determined by the length of a vector of non-minimal coupling in the space of scalar fields and its orientation relative to the mass eigenvectors. Using data from the Cassini tracking experiment, we estimate bounds on a general theory with two scalar fields. Our formalism can be utilized for a wide range of models, which we illustrate by applying it to nonminimally coupled Higgs SU(2) doublet, general hybrid metric-Palatini gravity, linear (${\square }^{-1}$) and quadratic (${\square }^{-2}$) nonlocal gravity.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2016)·38 citations
22. 22*

    Doubly assisted Sauter-Schwinger effect

    Greger Torgrimsson🇩🇪 · Johannes Oertel🇩🇪 · Ralf Schützhold🇩🇪

    We study electron-positron pair creation by a strong and slowly varying electric field, assisted by a weaker and more rapidly changing field (e.g., in the keV regime) plus an additional high-energy (say MeV) photon. It turns out that this combination can yield a pair creation probability which is exponentially larger than in the case where one (or more) of the three ingredients is missing. Apart from a deeper understanding of these non-perturbative phenomena, this double enhancement may pave the way for an experimental verification of this fundamental prediction.

    ↳ hep-thhep-phquant-phPRD(2016)·36 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.