Thu·Feb 4, 2016Thursday·February 4, 2016

1. 01*

   Theoretical Developments in QCD Jet Energy Loss

   Yacine Mehtar-Tani🇺🇸

   We review the recent developments in the theory of jet-quenching. First, we analyze the coherent vacuum cascade and incoherent medium-induced cascade separately. We then discuss the interplay between the two kinds of cascade and the resulting partial decoherence of the inner jet structure. Finally, we report on recent calculations of higher-order corrections. In particular, the dominant radiative corrections to jet observables that yield the renormalization of the jet-quenching parameter are addressed.

   hep-phnucl-thNPA(2016)·5 citations
2. 02*

   Nonlinear lepton-photon interactions in external background fields

   Ibrahim Akal🇩🇪 · Gudrid Moortgat-Pick🇩🇪

   Nonlinear phenomena of lepton-photon interactions in external backgrounds with a generalised periodic plane-wave geometry are studied. We discuss nonlinear Compton scattering in head-on lepton-photon collisions extended properly to beyond the soft-photon regime. In addition, our results are applied to stimulated lepton-antilepton pair production in photon collisions with unrestricted energies. Derivations are considered semi-classically based on unperturbed fermionic Volkov representations encoding the full interaction with the background field. Closed expressions for total probabilities considering S-matrix elements have been derived. The general formula is applied to Compton scattering by an electron propagating in an external laser-like background. We obtain additive contributions in the extended unconstrained result which turns out to be stringently required in the highly nonlinear regime. A detailed comparison of contributing harmonics is discussed for various field parameters.

   hep-ph3 citations
3. 03*

   Broadband and Resonant Approaches to Axion Dark Matter Detection

   Yonatan Kahn🇺🇸 · Benjamin R. Safdi🇺🇸 · Jesse Thaler🇺🇸

   When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. We propose a new experiment to detect this axion effective current. In the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. We consider both resonant and broadband readout circuits and show that a broadband approach has advantages at small axion masses. We estimate the reach of this design, taking into account the irreducible sources of noise, and demonstrate potential sensitivity to axion-like dark matter with masses in the range of 10^{-14}-10^{-6} eV. In particular, both the broadband and resonant strategies can probe the QCD axion with a GUT-scale decay constant.

   hep-phastro-ph.COhep-exphysics.ins-detPRL(2016)·451 citations
4. 04*

   A Composite Model for the 750 GeV Diphoton Excess

   Keisuke Harigaya🇺🇸 · Yasunori Nomura🇺🇸

   We study a simple model in which the recently reported 750 GeV diphoton excess arises from a composite pseudo Nambu-Goldstone boson---hidden pion---produced by gluon fusion and decaying into two photons. The model only introduces an extra hidden gauge group at the TeV scale with a vectorlike quark in the bifundamental representation of the hidden and standard model gauge groups. We calculate the masses of all the hidden pions and analyze their experimental signatures and constraints. We find that two colored hidden pions must be near the current experimental limits, and hence are probed in the near future. We study physics of would-be stable particles---the composite states that do not decay purely by the hidden and standard model gauge dynamics---in detail, including constraints from cosmology. We discuss possible theoretical structures above the TeV scale, e.g. conformal dynamics and supersymmetry, and their phenomenological implications. We also discuss an extension of the minimal model in which there is an extra hidden quark that is singlet under the standard model and has a mass smaller than the hidden dynamical scale. This provides two standard model singlet hidden pions that can both be viewed as diphoton/diboson resonances produced by gluon fusion. We discuss several scenarios in which these (and other) resonances can be used to explain various excesses seen in the LHC data.

   hep-phhep-exJHEP(2016)·51 citations
5. 05*

   Inclusive jet spectrum for small-radius jets

   Mrinal Dasgupta🇬🇧 · Frédéric A. Dreyer🇨🇭 · Gavin P. Salam🇨🇭 · Gregory Soyez🇫🇷

   Following on our earlier work on leading-logarithmic (LLR) resummations for the properties of jets with a small radius, R, we here examine the phenomenological considerations for the inclusive jet spectrum. We discuss how to match the NLO predictions with small-R resummation. As part of the study we propose a new, physically-inspired prescription for fixed-order predictions and their uncertainties. We investigate the R-dependent part of the next-to-next-to-leading order (NNLO) corrections, which is found to be substantial, and comment on the implications for scale choices in inclusive jet calculations. We also examine hadronisation corrections, identifying potential limitations of earlier analytical work with regards to their $p_t$-dependence. Finally we assemble these different elements in order to compare matched (N)NLO+LLR predictions to data from ALICE and ATLAS, finding improved consistency for the R-dependence of the results relative to NLO predictions.

   hep-phhep-exJHEP(2016)·136 citations
6. 06*

   Searching for $\tau \to \mu \gamma$ lepton-flavor-violating decay at super charm-tau factory

   Zhou Hao🇨🇳 · Zhang Ren-You🇨🇳 · Han Liang🇨🇳 · Ma Wen-Gan🇨🇳 · Guo Lei🇨🇳 · Chen Chong🇨🇳

   We investigate the possibility of searching the lepton-flavor-violating (LFV) $\tau \to \mu \gamma$ rare decay at the Super Charm-Tau Factory (CTF). By comparing the kinematic distributions of the LFV signal and the standard model (SM) background, we develop an optimized event selection criteria which can significantly reduce the background events. It is concluded that new $2\sigma$ upper limit of about $1.9\times 10^{-9}$ on $Br(\tau \to \mu \gamma )$ can be obtained at the CTF, which is beyond the capability of Super-B factory in searching $\tau$ lepton rare decay. Within the framework of the scalar leptoquark model, a joint constraint on ${\lambda }_1{\lambda }_2$ and $M_{LQ}$ can be derived from the upper bound on $Br(\tau \to \mu \gamma )$. With $1000f{b}^{-1}$ data expected at the CTF, we get ${\lambda }_1{\lambda }_2<7.2\times 10^{-2}(M_{LQ}=800\mathrm{GeV})$ and $M_{LQ}>900\mathrm{GeV}({\lambda }_1{\lambda }_2=9\times 10^{-2})$ at $95\%$ confidence level (C.L.).

   hep-phEPJC(2016)·6 citations
7. 07*

   Di-Higgs Decay of Stoponium at Future Photon-Photon Collider

   Hayato Ito🇯🇵 · Takeo Moroi🇯🇵 · Yoshitaro Takaesu🇯🇵

   We study the detectability of the stoponium in the di-Higgs decay mode at the photon-photon collider option of the International $e^{+}{e}^{-}$ Linear Collider (ILC), whose center-of-mass energy is planned to reach $\sim 1$ TeV. We find that $5\sigma$ detection of the di-Higgs decay mode is possible with the integrated electron-beam luminosity of $1{\mathrm{ab}}^{-1}$ if the signal cross section, $\sigma (\gamma \gamma \to {\sigma }_{{\tilde{t}}_1}\to hh)$, of $\mathcal{O}(0.1)$ fb is realized for the stoponium mass smaller than $\sim$ 800 GeV at 1 TeV ILC. Such a value of the cross section can be realized in the minimal supersymmetric standard model (MSSM) with relatively large trilinear stop-stop-Higgs coupling constant. Implication of the stoponium cross section measurement for the MSSM stop sector is also discussed.

   hep-phPRD(2016)·3 citations
8. 08*

   Search for $XYZ$ states in ${\Lambda }_b$ decays at the LHCb

   Y.K. Hsiao🇨🇳 · C.Q. Geng🇨🇳

   We consider $X(3872)$ and $Y(4140)$ as the vector tetraquark states of $X_c^0\equiv c\bar{c}u\bar{u}(d\bar{d})$ and $c\bar{c}s\bar{s}$, respectively. By connecting ${\Lambda }_b\to X_c^0\Lambda$ to $B^{-}\to X_c^0{K}^{-}$, we predict that the branching ratios of ${\Lambda }_b\to \Lambda (X(3872{)}^0\to )J/\psi {\pi }^{+}{\pi }^{-}$ and ${\Lambda }_b\to \Lambda (Y(4140)\to )J/\psi \varphi$ are $(5.2\pm 1.8)\times 10^{-6}$ and $(4.7\pm 2.6)\times 10^{-6}$, which are accessible to the experiments at the LHCb, respectively. The measurements of these ${\Lambda }_b$ modes would be the first experimental evidences for the $XYZ$ states in baryonic decays.

   hep-phhep-exPLB(2016)·8 citations
9. 09*

   Probing Compositeness with the CMS $eejj$ & $eej$ Data

   Tanumoy Mandal🇸🇪 · Subhadip Mitra🇮🇳 · Satyajit Seth🇩🇪

   Quark-lepton compositeness is a well-known beyond the Standard Model (SM) scenario with heavy exotic particles like leptoquarks (LQs) and leptogluons (LGs) etc. These particles can couple to leptons and jets simultaneously. In this letter, we use the recent CMS scalar LQ search data in the $eejj$ and $eej$ channels to probe this scenario. We recast the data in terms of a color octet partner of the SM electron (or a first generation spin-1/2 LG) that couples to an electron and a gluon via a dimension five operator suppressed by the quark-lepton compositeness scale ($\Lambda$). By combining different production processes of the color octet electron ($e_8$) at the LHC, we use the CMS 8TeV data to obtain a simultaneous bound on $\Lambda$ and the mass of the $e_8$ ($M_{e_8}$). We also study the reach of the 13 TeV LHC to discover the $e_8$ and interpret the required luminosity in terms of $M_{e_8}$ and $\Lambda$.

   hep-phhep-exPLB(2016)·25 citations
10. 10*

    Equation of state of imbalanced cold matter from chiral perturbation theory

    Stefano Carignano🇮🇹 · Andrea Mammarella🇮🇹 · Massimo Mannarelli🇮🇹

    We study the thermodynamic properties of matter at vanishing temperature for non-extreme values of the isospin chemical potential and of the strange quark chemical potential. From the leading order pressure obtained by maximizing the static chiral Lagrangian density we derive a simple expression for the equation of state in the pion condensed phase and in the kaon condensed phase. We find an analytical expression for the maximum of the ratio between the energy density and the Stefan-Boltzmann energy density as well as for the isospin chemical potential at the peak both in good agreement with lattice simulations of quantum chromodynamics. We speculate on the location of the crossover from the Bose-Einstein condensate state to the Bardeen-Cooper-Schrieffer state by a simple analysis of the thermodynamic properties of the system. For ${\mu }_I\gtrsim 2m_{\pi }$ the leading order chiral perturbation theory breaks down; as an example it underestimates the energy density of the system and leads to a wrong asymptotic behavior.

    hep-phastro-ph.HEcond-mat.quant-gashep-latPRD(2016)·35 citations
11. 11*

    Extending the velocity-dependent one-scale model for domain walls

    C. J. A. P. Martins🇵🇹 · I. Yu. Rybak🇵🇹 · A. Avgoustidis🇬🇧 · E. P. S. Shellard🇬🇧

    We report on an extensive study of the evolution of domain wall networks in Friedmann-Lema\^ıtre-Robertson-Walker universes by means of the largest currently available field-theory simulations. These simulations were done in $4096^3$ boxes and for a range of different fixed expansion rates, as well as for the transition between the radiation and matter eras. A detailed comparison with the velocity-dependent one-scale (VOS) model shows that this cannot accurately reproduce the results of the entire range of simulated regimes if one assumes that the phenomenological energy loss and momentum parameters are constants. We therefore discuss how a more accurate modeling of these parameters can be done, specifically by introducing an additional mechanism of energy loss (scalar radiation, which is particularly relevant for regimes with relatively little damping) and a modified momentum parameter which is a function of velocity (in analogy to what was previously done for cosmic strings). We finally show that this extended model, appropriately calibrated, provides an accurate fit to our simulations.

    hep-phastro-ph.COgr-qchep-thPRD(2016)·81 citations
12. 12*

    Nambu-Jona-Lasinio Theory and Dynamical Breaking of Supersymmetry

    Nobuhito Maru🇯🇵

    A recently proposed new mechanism of D-term triggered dynamical supersymmetry breaking is reviewed. Supersymmetry is dynamically broken by nonvanishing D-term vacuum expectation value, which is realized as a nontrivial solution of the gap equation in the self-consistent approximation as in the case of Nambu-Jona-Lasinio model and BCS superconductivity.

    hep-phhep-thPTEP(2016)·0 citations
13. 13*

    On $J^{PC}=0^{--}$ exotic glueball

    Loredana Bellantuono🇮🇹

    The mass spectrum of the gluonium with $J^{PC}=0^{--}$ is examined in three bottom-up AdS/QCD models. The results are used to identify several production and decay modes useful for searching this state. Moreover, the properties of such glueball in a hot and dense quark medium are discussed.

    hep-phFew Body Syst.(2016)·0 citations
14. 14*

    Strong electroweak phase transition from Supersymmetric Custodial Triplets

    Mateo Garcia-Pepin🇪🇸 · Mariano Quiros🇪🇸

    The Supersymmetric Custodial Triplet Model, a supersymmetric generalization of the Georgi-Machacek model, has proven to be an interesting modification of the MSSM. It extends the MSSM Higgs sector by three extra SU(2)L triplets in such a way that approximate custodial invariance is preserved and rho-parameter deviations are kept under control. By means of a sizeable triplet contribution to electroweak breaking the model is able to generate a barrier at tree level between the false vacuum and the electroweak one. This will result in a strong first order phase transition for an important region of the parameter space. We also look at the gravitational waves that could be generated as a result of the phase transition and show how future interferometers could be used as a probe of the model.

    hep-phastro-ph.COJHEP(2016)·26 citations
15. 15*

    On Exclusive $h\to V{\ell }^{+}{\ell }^{-}$ Decays

    Pietro Colangelo🇮🇹 · Fulvia De Fazio🇮🇹 · Pietro Santorelli🇮🇹

    We study a set of exclusive decay modes of the Standard Model Higgs boson into a vector meson and a dilepton pair: $h\to V{\ell }^{+}{\ell }^{-}$, with $V={\rm Y},J/\psi ,\varphi$, and $\ell =\mu ,\tau$, determining the decay rates, the dilepton mass spectra and the $V$ longitudinal helicity fraction distributions. In the same framework, we analyze the exclusive modes into neutrino pairs $h\to V\nu \bar{\nu }$. We also discuss the implications of the recent CMS and ATLAS results for the lepton flavor-changing process $h\to {\tau }^{+}{\mu }^{-}$ on the $h\to V{\tau }^{+}{\mu }^{-}$ decay modes.

    hep-phPLB(2016)·8 citations
16. 16*

    A Flippon Related Singlet at the LHC II

    Tianjun Li🇨🇳 · James A. Maxin🇺🇸 · Van E. Mayes🇺🇸 · Dimitri V. Nanopoulos🇺🇸

    We consider the 750 GeV diphoton resonance at the 13 TeV LHC in the $\mathcal{F}$-$SU(5)$ model with a Standard Model (SM) singlet field which couples to TeV-scale vector-like particles, dubbed $flippons$. This singlet field assumes the role of the 750 GeV resonance, with production via gluon fusion and subsequent decay to a diphoton via the vector-like particle loops. We present a numerical analysis showing that the observed 8 TeV and 13 TeV diphoton production cross-sections can be generated in the model space with realistic electric charges and Yukawa couplings for light vector-like masses. We further discuss the experimental viability of light vector-like masses in a General No-Scale $\mathcal{F}$-$SU(5)$ model, offering a few benchmark scenarios in this consistent GUT that can satisfy all experimental constraints imposed by the LHC and other essential experiments.

    hep-phJHEP(2016)·25 citations
17. 17*

    Assessing the role of nuclear effects in the interpretation of the MiniBooNE low-energy anomaly

    M. Ericson🇨🇭 · M. V. Garzelli🇩🇪 · C. Giunti🇮🇹 · M. Martini🇫🇷

    We study the impact of the effect of multinucleon interactions in the reconstruction of the neutrino energy on the fit of the MiniBooNE data in terms of neutrino oscillations. We obtain some improvement of the fit of the MiniBooNE low-energy excess in the framework of two-neutrino oscillations and a shift of the allowed region in the ${\sin }^{2}2\vartheta$--$\Delta m^2$ plane towards smaller values of ${\sin }^{2}2\vartheta$ and larger values of $\Delta m^2$. However this effect is not enough to solve the problem of the appearance-disappearance tension in the global fit of short-baseline neutrino oscillation data.

    hep-phhep-exnucl-thPRD(2016)·24 citations
18. 18*

    Chiral current generation in QED by longitudinal photons

    J. L. Acosta Avalo🇨🇺 · H. Perez Rojas🇨🇺

    We report the generation of a pseudovector electric current having imbalanced chirality in an electron-positron strongly magnetized gas in QED. It propagates along the external applied magnetic field B as a chiral magnetic effect in QED. It is triggered by a perturbative electric field parallel to B, associated to a pseudovector longitudinal mode propagating along B. An electromagnetic chemical potential was introduced, but our results remain valid even for vanishing chemical potential. A nonzero fermion mass was assumed, which is usually considered vanishing in the literature. In the quantum field theory formalism at finite temperature and density, an anomaly relation for the axial current was found for a medium of massive fermions. It bears some analogy to the Adler-Bell-Jackiw anomaly. From the expression for the chiral current in terms of the photon self-energy tensor in a medium, it is obtained that electrons and positrons scattered by longitudinal photons (inside the light cone) contribute to the chiral current, as well as the pair creation due to longitudinal photons (out of light cone). In the static limit, an electric pseudovector current is obtained in the lowest Landau level

    hep-phNPB(2016)·5 citations
19. 19*

    Comment on "Breakdown of the expansion of finite-size corrections to the hydrogen Lamb shift in moments of charge distribution"

    J. Arrington🇺🇸

    In a recent paper, Hagelstein and Pascalutsa examine the error associated with an expansion of proton structure corrections to the Lamb shift in terms of moments of the charge distribution. They propose a small modification to a conventional parameterization of the proton's charge form factor and show that this can resolve the proton radius puzzle. However, while the size of the "bump" they add to the form factor is small, it is large compared to the total proton structure effects in the initial parameterization, yielding a final form factor that is unphysical. Reducing their modification to the point where the resulting form factor is physical does not allow for a resolution of the radius puzzle.

    hep-phnucl-thphysics.atom-phPRA(2016)·3 citations
20. 20*

    A direct approach to quantum tunneling

    Anders Andreassen🇺🇸 · David Farhi🇺🇸 · William Frost🇺🇸 · Matthew D. Schwartz🇺🇸

    The decay rates of quasistable states in quantum field theories are usually calculated using instanton methods. Standard derivations of these methods rely in a crucial way upon deformations and analytic continuations of the physical potential, and on the saddle point approximation. While the resulting procedure can be checked against other semi-classical approaches in some one-dimensional cases, it is challenging to trace the role of the relevant physical scales, and any intuitive handle on the precision of the approximations involved are at best obscure. In this paper, we use a physical definition of the tunneling probability to derive a formula for the decay rate in both quantum mechanics and quantum field theory directly from the Minkowski path integral, without reference to unphysical deformations of the potential. There are numerous benefits to this approach, from non-perturbative applications to precision calculations and aesthetic simplicity.

    ↳ hep-thhep-phPRL(2016)·70 citations
21. 21*

    Ruling out the light WIMP explanation of the galactic 511 keV line

    Ryan J. Wilkinson🇬🇧 · Aaron C. Vincent🇬🇧 · Celine Boehm🇬🇧 · Christopher McCabe🇳🇱

    Over the past few decades, an anomalous 511 keV gamma-ray line has been observed from the centre of the Milky Way. Dark matter (DM) in the form of light weakly interacting massive particles (WIMPs) annihilating into electron-positron pairs has been one of the leading hypotheses of the observed emission. Given the small required cross section, a further coupling to lighter particles is required to produce the correct relic density. Here, we derive constraints from the Planck satellite on light WIMPs that were in equilibrium with either the neutrino or electron sector in the early universe. For the neutrino sector, we obtain a lower bound on the WIMP mass of 4 MeV for a real scalar and 10 MeV for a Dirac fermion DM particle, at 95% CL. For the electron sector, we find even stronger bounds of 7 and 11 MeV, respectively. Using these results, we show that, in the absence of additional ingredients such as dark radiation, the light thermally produced WIMP explanation of the 511 keV excess is strongly disfavoured by the latest cosmological data. This suggests an unknown astrophysical or more exotic DM source of the signal.

    ↳ astro-ph.COhep-phPRD(2016)·79 citations
22. 22*

    Efficient formulas for efficiency correction of cumulants

    Masakiyo Kitazawa🇯🇵

    We derive formulas which connect cumulants of particle numbers observed with efficiency losses with the original ones based on the binomial model. These formulas can describe the case with multiple efficiencies in a compact form. Compared with the presently suggested ones based on factorial moments, these formulas would drastically reduce the numerical cost for efficiency corrections when the order of the cumulant and the number of different efficiencies are large. The efficiency correction with realistic $p_T$-dependent efficiency would be carried out with the aid of these formulas.

    ↳ nucl-thhep-phnucl-exPRC(2016)·38 citations
23. 23*

    Holographic Equilibration of Nonrelativistic Plasmas

    Umut Gürsoy🇳🇱 · Aron Jansen🇳🇱 · Watse Sybesma🇳🇱 · Stefan Vandoren🇳🇱

    We study far-from-equilibrium physics of strongly interacting plasmas at criticality and zero charge density for a wide range of dynamical scaling exponents z in d dimensions using holographic methods. In particular, we consider homogeneous isotropization of asymptotically Lifshitz black branes with full backreaction. We find stable evolution and equilibration times that exhibit small dependence of z and are of the order of the inverse temperature. Performing a quasinormal mode analysis we find a corresponding narrow range of relaxation times, fully characterized by the fraction z/(d-1). For z>=d-1, equilibration is overdamped, whereas for z<d-1 we find oscillatory behavior.

    ↳ hep-thgr-qchep-phPRL(2016)·29 citations
24. 24*

    ${\Lambda }_b\to \Lambda {\ell }^{+}{\ell }^{-}$ form factors, differential branching fraction, and angular observables from lattice QCD with relativistic $b$ quarks

    William Detmold🇺🇸 · Stefan Meinel🇺🇸

    Using $(2+1)$-flavor lattice QCD, we compute the 10 form factors describing the ${\Lambda }_b\to \Lambda$ matrix elements of the $b\to s$ vector, axial vector, and tensor currents. The calculation is based on gauge field ensembles generated by the RBC and UKQCD Collaborations with a domain-wall action for the $u$, $d$, and $s$ quarks and the Iwasaki gauge action. The $b$ quark is implemented using an anisotropic clover action, tuned nonperturbatively to the physical point, and the currents are renormalized with a mostly nonperturbative method. We perform simultaneous chiral, continuum, and kinematic extrapolations of the form factors through modified $z$ expansions. Using our form factor results, we obtain precise predictions for the ${\Lambda }_b\to \Lambda (\to p^{+}{\pi }^{-}){\mu }^{+}{\mu }^{-}$ differential branching fraction and angular observables in the Standard Model.

    ↳ hep-lathep-exhep-phPRD(2016)·182 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.