Wed·Feb 10, 2016Wednesday·February 10, 2016

1. 01*

   GPD phenomenology and DVCS fitting - Entering the high-precision era

   K. Kumericki🇭🇷 · S. Liuti🇺🇸 · H. Moutarde🇫🇷

   We review the phenomenological framework for accessing Generalized Parton Distributions (GPDs) using measurements of Deeply Virtual Compton Scattering (DVCS) from a proton target. We describe various GPD models and fitting procedures, emphasizing specific challenges posed both by the internal structure and properties of the GPD functions and by their relation to observables. Bearing in mind forthcoming data of unprecedented accuracy, we give a set of recommendations to better define the pathway for a precise extraction of GPDs from experiment.

   hep-phEPJA(2016)·257 citations
2. 02*

   Collective neutrino flavor conversion: Recent developments

   Sovan Chakraborty🇩🇪 · Rasmus Sloth Hansen🇩🇪 · Ignacio Izaguirre🇩🇪 · Georg Raffelt🇩🇪

   Neutrino flavor evolution in core-collapse supernovae, neutron-star mergers, or the early universe is dominated by neutrino-neutrino refraction, often spawning "self-induced flavor conversion", i.e., shuffling of flavor among momentum modes. This effect is driven by collective run-away modes of the coupled "flavor oscillators" and can spontaneously break the initial symmetries such as axial symmetry, homogeneity, isotropy, and even stationarity. Moreover, the growth rates of unstable modes can be of the order of the neutrino-neutrino interaction energy instead of the much smaller vacuum oscillation frequency: self-induced flavor conversion does not always require neutrino masses. We illustrate these newly found phenomena in terms of simple toy models. What happens in realistic astrophysical settings is up to speculation at present.

   hep-phastro-ph.SRNPB(2016)·233 citations
3. 03*

   Gravitational perturbations of the Higgs field

   Franco D. Albareti🇪🇸 · Antonio L. Maroto🇪🇸 · Francisco Prada🇪🇸

   We study the possible effects of classical gravitational backgrounds on the Higgs field through the modifications induced in the one-loop effective potential and the vacuum expectation value of the energy-momentum tensor. We concentrate our study on the Higgs self-interaction contribution in a perturbed FRW metric. For weak and slowly varying gravitational fields, a complete set of mode solutions for the Klein-Gordon equation is obtained to leading order in the adiabatic approximation. Dimensional regularization has been used in the integral evaluation and a detailed study of the integration of nonrational functions in this formalism has been presented. As expected, the regularized effective potential contains the same divergences as in flat spacetime, which can be renormalized without the need of additional counterterms. We find that, in contrast with other regularization methods, even though metric perturbations affect the mode solutions, they do not contribute to the leading adiabatic order of the potential. We also obtain explicit expressions of the complete energy-momentum tensor for general nonminimal coupling in terms of the perturbed modes. The corresponding leading adiabatic contributions are also obtained.

   hep-phastro-ph.COgr-qcPRD(2017)·7 citations
4. 04*

   Closing the Wedge: Search Strategies for Extended Higgs Sectors with Heavy Flavor Final States

   Stefania Gori🇨🇦 · Ian-Woo Kim🇨🇭 · Nausheen R. Shah🇺🇸 · Kathryn M. Zurek🇺🇸

   We consider search strategies for an extended Higgs sector at the high-luminosity LHC14 utilizing multi-top final states. In the framework of a Two Higgs Doublet Model, the purely top final states ($t\bar{t},4t$) are important channels for heavy Higgs bosons with masses in the wedge above $2m_t$ and at low values of $\tan \beta$, while a $2b2t$ final state is most relevant at moderate values of $\tan \beta$. We find, in the $t\bar{t}H$ channel, with $H\to t\bar{t}$, that both single and 3 lepton final states can provide statistically significant constraints at low values of $\tan \beta$ for $m_A$ as high as $\sim 750$ GeV. When systematics on the $t\bar{t}$ background are taken into account, however, the 3 lepton final state is more powerful, though the precise constraint depends fairly sensitively on lepton fake rates. We also find that neither $2b2t$ nor $t\bar{t}$ final states provide constraints on additional heavy Higgs bosons with couplings to tops smaller than the top Yukawa due to expected systematic uncertainties in the $t\bar{t}$ background.

   hep-phhep-exPRD(2016)·67 citations
5. 05*

   Electron contribution to the muon anomalous magnetic moment at four loops

   Alexander Kurz🇩🇪 · Tao Liu🇨🇦 · Peter Marquard🇩🇪 · Alexander Smirnov🇷🇺 · Vladimir Smirnov🇷🇺 · Matthias Steinhauser🇩🇪

   We present results for the QED contributions to the anomalous magnetic moment of the muon containing closed electron loops. The main focus is on perturbative corrections at four-loop order where the external photon couples to the external muon. Furthermore, all four-loop contributions involving simultaneously a closed electron and tau loop are computed. In combination with our recent results on the light-by-light-type corrections (see Ref. \cite{Kurz:2015bia}) the complete four-loop electron-loop contribution to the anomalous magnetic moment of the muon has been obtained with an independent calculation. Our calculation is based on an asymptotic expansion in the ratio of the electron and the muon mass and shows the importance of higher order terms in this ratio. We perform a detailed comparison with results available in the literature and find good numerical agreement. As a by-product we present analytic results for the on-shell muon mass and wave function renormalization constants at three-loop order including massive closed electron and tau loops, which we also calculated using the method of asymptotic expansion.

   hep-phPRD(2016)·50 citations
6. 06*

   UV contribution and power dependence on ${\Lambda }_{\mathrm{QCD}}$ of Adler function

   Go Mishima🇯🇵 · Yukinari Sumino🇯🇵 · Hiromasa Takaura🇯🇵

   We formulate a way to separate UV and IR contributions to the Adler function and discuss how ${\Lambda }_{\mathrm{QCD}}^2/Q^2$ dependence is encoded in the UV contribution within perturbative QCD.

   hep-phPLB(2016)·6 citations
7. 07*

   Kaluza-Klein graviton phenomenology for warped compactifications, and the 750 GeV diphoton excess

   Steven B. Giddings🇺🇸 · Hao Zhang🇺🇸

   A generic prediction of scenarios with extra dimensions accessible in TeV-scale collisions is the existence of Kaluza-Klein excitations of the graviton. For a broad class of strongly-warped scenarios one expects to initially find an isolated resonance, whose phenomenology in the simplest cases is described by a simplified model with two parameters, its mass, and a constant $\Lambda$ with units of mass parameterizing its coupling to the Standard Model stress tensor. These parameters are in turn determined by the geometrical configuration of the warped compactification. We explore the possibility that the 750 GeV excess recently seen in 13 TeV data at ATLAS and CMS could be such a warped Kaluza-Klein graviton, and find a best-fit value $\Lambda \approx 60$ TeV. We find that while there is some tension between this interpretation and data from 8 TeV and from the dilepton channel at 13 TeV, it is not strongly excluded. However, in the simplest scenarios of this kind, such a signal should soon become apparent in both diphoton and dilepton channels.

   hep-phhep-exhep-thPRD(2016)·45 citations
8. 08*

   Drell-Yan as an avenue to test noncommutative Standard Model at the Large Hadron Collider

   J Selvaganapathy🇮🇳 · Prasanta Kumar Das🇮🇳 · Partha Konar🇮🇳

   We study the Drell-Yan process at the Large Hadron Collider in presence of the noncommutative extension of standard model. Using the Seiberg-Witten map, we calculate the production cross-section to the first order in the noncommutative parameter ${\Theta }_{\mu \nu }$. Although this idea is evolving for long, limited amount of phenomenological analysis was done so far and dominantly in the context of linear collider. Some outstanding feature from this non-minimal noncommutative standard model not only modify the couplings over SM production channel, also allow additional nonstandard vertices which can play a significant role. Hence in the Drell-Yan process, as studied in present analysis, one also needs to account for gluon fusion process at the tree level. Some of the characteristic signatures such as oscillatory azimuthal distributions are outcome of the momentum dependent effective couplings. We explore the noncommutative scale ${\Lambda }_{NC}\ge 0.4\mathrm{TeV}$ considering different machine energy ranging from $7\mathrm{TeV}$ to $13\mathrm{TeV}$.

   hep-phhep-exPRD(2016)·20 citations
9. 09*

   Why three generations?

   Masahiro Ibe🇯🇵 · Alexander Kusenko🇯🇵 · Tsutomu T. Yanagida🇯🇵

   We discuss an anthropic explanation of why there exist three generations of fermions. If one assumes that the right-handed neutrino sector is responsible for both the matter-antimatter asymmetry and the dark matter, then anthropic selection favors three or more families of fermions. For successful leptogenesis, at least two right-handed neutrinos are needed, while the third right-handed neutrino is invoked to play the role of dark matter. The number of the right-handed neutrinos is tied to the number of generations by the anomaly constraints of the $U(1{)}_{B-L}$ gauge symmetry. Combining anthropic arguments with observational constraints, we obtain predictions for the $X$-ray observations, as well as for neutrinoless double-beta decay.

   hep-phPLB(2016)·28 citations
10. 10*

    Angular distributions of $\bar{B}\to D^{(\ast )}\ell {\bar{\nu }}_{\ell }$ decays and search of New Physics

    Damir Becirevic🇫🇷 · Svjetlana Fajfer🇸🇮 · Ivan Nisandzic🇩🇪 · Andrey Tayduganov🇫🇷

    We derive the expressions for the full angular distributions of $\bar{B}\to D\ell {\bar{\nu }}_{\ell }$ and $\bar{B}\to D^{\ast }\ell {\bar{\nu }}_{\ell }$ decays and discuss the spectra on each angle separately. The coefficient functions, depending on helicity amplitudes, can then be combined in an ensemble of observables which can then be used to check for the presence of New Physics. We examine the sensitivity of each of these observables on the presence of non-Standard Model interaction terms at low energies. The expressions presented here are general and can be used for studying any other semileptonic pseudoscalar to pseudoscalar/vector meson decay. We also examine the problem of pollution of the $\bar{B}\to D^{\ast }(\to D\pi {)}_S\ell {\bar{\nu }}_{\ell }$ decay sample by the $\bar{B}\to D_0^{\ast }(\to D\pi )\ell {\bar{\nu }}_{\ell }$ events, and point out that a measurement of two particular quantities could clarify whether or not the $(D\pi {)}_{S-\mathrm{wave}}$ in the vicinity of $D^{\ast }$-peak is (approximately) described by the Breit-Wigner formula.

    hep-phhep-exhep-latNPB(2019)·111 citations
11. 11*

    ${\gamma }_{\mathbf{v}}\mathbf{N}{\mathbf{N}}^{\ast }$ Electrocouplings in Dyson-Schwinger Equations

    Jorge Segovia🇩🇪

    A symmetry preserving framework for the study of continuum Quantum Chromodynamics (QCD) is obtained from a truncated solution of the QCD equations of motion or QCD's Dyson-Schwinger equations (DSEs). A nonperturbative solution of the DSEs enables the study of, e.g., hadrons as composites of dressed-quarks and dressed-gluons, the phenomena of confinement and dynamical chiral symmetry breaking (DCSB), and therefrom an articulation of any connection between them. It is within this context that we present a unified study of Nucleon, Delta and Roper elastic and transition electromagnetic form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector$\otimes$vector contact-interaction. The comparison emphasises that experiment is sensitive to the momentum dependence of the running coupling and masses in QCD and highlights that the key to describing hadron properties is a veracious expression of dynamical chiral symmetry breaking in the bound-state problem.

    ↳ nucl-thhep-exhep-lathep-phFew Body Syst.(2016)·5 citations
12. 12*

    Mode-coupling effects in anisotropic flow in heavy-ion collisions

    Jing Qian (Ohio State and Harbin Institute of Technology)🇨🇳 · Ulrich W. Heinz (Ohio State)🇺🇸 · Jia Liu (Ohio State)🇺🇸

    Higher-order anisotropic flows in heavy-ion collisions are affected by nonlinear mode coupling effects. It has been suggested that the associated nonlinear hydrodynamic response coefficients probe the transport properties and are largely insensitive to the spectrum of initial density fluctuations of the medium created in these collisions. To test this suggestion, we explore nonlinear mode coupling effects in event-by-event viscous fluid dynamics, using two different models for the fluctuating initial density profiles, and compare the nonlinear coupling coefficients between the initial eccentricity vectors before hydrodynamic expansion and the final flow vectors after the expansion. For several mode coupling coefficients we find significant sensitivity to the initial fluctuation spectrum. They all exhibit strong sensitivity to the specific shear viscosity at freeze-out, but only weak dependence on the shear viscosity during hydrodynamic evolution.

    ↳ nucl-thhep-phnucl-exPRC(2016)·87 citations
13. 13*

    Oscillating propagators in heavy-dense QCD

    Oscar Akerlund🇨🇭 · Philippe de Forcrand🇨🇭 · Tobias Rindlisbacher🇨🇭

    Using Monte Carlo simulations and extended mean field theory calculations we show that the $3$-dimensional $Z_3$ spin model with complex external fields has non-monotonic spatial correlators in some regions of its parameter space. This model serves as a proxy for heavy-dense QCD in $(3+1)$ dimensions. Non-monotonic spatial correlators are intrinsically related to a complex mass spectrum and a liquid-like (or crystalline) behavior. A liquid phase could have implications for heavy-ion experiments, where it could leave detectable signals in the spatial correlations of baryons.

    ↳ hep-latcond-mat.stat-mechhep-phJHEP(2016)·24 citations
14. 14*

    Heterotic free fermionic and symmetric toroidal orbifold models

    P. Athanasopoulos🇬🇧 · A.E. Faraggi🇬🇧 · S. Groot Nibbelink🇩🇪 · V.M. Mehta🇩🇪

    Free fermionic models and symmetric heterotic toroidal orbifolds both constitute exact backgrounds that can be used effectively for phenomenological explorations within string theory. Even though it is widely believed that for Z2xZ2 orbifolds the two descriptions should be equivalent, a detailed dictionary between both formulations is still lacking. This paper aims to fill this gap: We give a detailed account of how the input data of both descriptions can be related to each other. In particular, we show that the generalized GSO phases of the free fermionic model correspond to generalized torsion phases used in orbifold model building. We illustrate our translation methods by providing free fermionic realizations for all Z2xZ2 orbifold geometries in six dimensions.

    ↳ hep-thhep-phJHEP(2016)·55 citations
15. 15*

    Gravitational wave production from the decay of the Standard Model Higgs field after inflation

    Daniel G. Figueroa🇨🇭 · Juan García-Bellido🇪🇸 · Francisco Torrentí🇪🇸

    During or towards the end of inflation, the Standard Model (SM) Higgs forms a condensate with a large amplitude. Following inflation, the condensate oscillates, decaying non-perturbatively into the rest of the SM species. The resulting out-of-equilibrium dynamics converts a fraction of the energy available into gravitational waves (GW). We study this process using classical lattice simulations in an expanding box, following the energetically dominant electroweak gauge bosons $W^{\pm }$ and $Z$. We characterize the GW spectrum as a function of the running couplings, Higgs initial amplitude, and post-inflationary expansion rate. As long as the SM is decoupled from the inflationary sector, the generation of this background is universally expected, independently of the nature of inflation. Our study demonstrates the efficiency of GW emission by gauge fields undergoing parametric resonance. The initial energy of the Higgs condensate represents however, only a tiny fraction of the inflationary energy. Consequently, the resulting background is very suppressed, with an amplitude $h^2{\Omega }_{\mathrm{GW}}^{(o)}\lesssim 10^{-29}$ today. The amplitude can be boosted to $h^2{\Omega }_{\mathrm{GW}}^{(o)}\lesssim 10^{-16}$, if following inflation the universe undergoes a kination-domination stage; however the background is shifted in this case to high frequencies $f_p\lesssim 10^{11}\mathrm{Hz}$. In all cases the signal is out of the range of current or planned GW detectors. This background will therefore remain, most likely, as a curiosity of the SM.

    ↳ astro-ph.COhep-phhep-thPRD(2016)·53 citations
16. 16*

    On possible tachyonic state of neutrino dark matter

    Maxim A. Makukov🇰🇿 · Eduard G. Mychelkin🇰🇿 · Vladimir L. Saveliev🇰🇿

    We revive the historically first dark matter model based on neutrinos, but with an additional assumption that neutrinos might exist in tachyonic almost sterile states. To this end, we propose a group-theoretical algorithm for the description of tachyons. The key point is that we employ a distinct tachyon Lorentz group with new (superluminal) parametrization which does not lead to violation of causality and unitarity. Our dark matter model represents effectively scalar tachyonic neutrino-antineutrino conglomerate. Distributed all over the universe, such fluid behaves as stable isothermal/stiff medium which produces somewhat denser regions (`halos') around galaxies and clusters. To avoid the central singularity inherent to the isothermal profile, we apply a special smoothing algorithm which yields density distributions and rotation curves consistent with observational data.

    ↳ physics.gen-phgr-qchep-phInt.J.Mod.Phys.Conf.Ser.(2016)·4 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.