Mon·Jul 27, 2015Monday·July 27, 2015

1. 01*

   Photon production from a non-equilibrium quark-gluon plasma

   Lusaka Bhattacharya🇺🇸 · Radoslaw Ryblewski🇵🇱 · Michael Strickland🇺🇸

   We calculate leading-order medium photon yields from a quark-gluon plasma using (3+1)-dimensional anisotropic hydrodynamics. Non-equilibrium corrections to the photon rate are taken into account using a self-consistent modification of the particle distribution functions and the corresponding anisotropic hard-loop fermionic self-energies. We present predictions for the high-energy photon spectrum and photon elliptic flow as a function of transverse momentum, shear viscosity, and initial momentum-space anisotropy. Our findings indicate that high-energy photon production is sensitive to the assumed level of initial momentum-space anisotropy of the quark-gluon plasma. As a result, it may be possible to experimentally constrain the early-time momentum-space anisotropy of the quark-gluon plasma generated in relativistic heavy-ion collisions using high-energy photon yields.

   hep-phnucl-thPRD(2016)·41 citations
2. 02*

   The resonant ${\pi }^{+}\gamma \to {\pi }^{+}{\pi }^0$ amplitude from Quantum Chromodynamics

   Raul A. Briceno🇺🇸 · Jozef J. Dudek🇺🇸 · Robert G. Edwards🇺🇸 · Christian J. Shultz🇺🇸 · Christopher E. Thomas🇬🇧 · David J. Wilson🇺🇸

   We present the first ab initio calculation of a radiative transition of a hadronic resonance within quantum chromodynamics (QCD). We compute the amplitude for $\pi \pi \to \pi {\gamma }^{\star }$, as a function of the energy of the $\pi \pi$ pair and the virtuality of the photon, in the kinematic regime where $\pi \pi$ couples strongly to the unstable $\rho$ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to $m_{\pi }\approx 400$~MeV. We obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the $\rho$ pole and identify from its residue the $\rho \to \pi {\gamma }^{\star }$ form factor.

   hep-phhep-latnucl-thPRL(2015)·105 citations
3. 03*

   A Dark Matter Relic From Muon Anomalies

   Geneviève Bélanger🇫🇷 · Cédric Delaunay🇫🇷 · Susanne Westhoff🇺🇸

   We show that the recently reported anomalies in $b\to s{\mu }^{+}{\mu }^{-}$ transitions, as well as the long-standing $g_{\mu }-2$ discrepancy, can be addressed simultaneously by a new massive abelian gauge boson with loop-induced coupling to muons. Such a scenario typically leads to a stable dark matter candidate with a thermal relic density close to the observed value. Dark matter in our model couples dominantly to leptons, hence signals in direct detection experiments lie well below the current sensitivity. The LHC, in combination with indirect detection searches, can test this scenario through distinctive signatures with muon pairs and missing energy.

   hep-phhep-exPRD(2015)·150 citations
4. 04*

   Theory and Phenomenology of the Elementary Goldstone Higgs

   Helene Gertov🇩🇰 · Aurora Meroni🇩🇰 · Emiliano Molinaro🇩🇰 · Francesco Sannino🇩🇰

   We show, via a careful analytical and numerical analysis, that a pseudo Goldstone nature of the Higgs is naturally embodied by an elementary realization that also serves as ultraviolet completion. Renormalizability married to perturbation theory allows to precisely determine the quantum corrections of the theory while permitting to explore the underlying parameter space. By characterising the available parameter space of the extended Higgs sector we discover that the preferred electroweak alignment angle is centred around $\theta \simeq 0.02$, corresponding to the Higgs chiral symmetry breaking scale $f\simeq 14$TeV. The latter is almost 60 times higher than the Standard Model electroweak scale. However, due to the perturbative nature of the theory, the spectrum of the enlarged Higgs sector remains in the few TeV energy range. We also analyse precision constraints and the relevant phenomenological aspects of the theory.

   hep-phPRD(2015)·28 citations
5. 05*

   Towards more precise determinations of the CKM phase $\beta$

   Zoltan Ligeti🇺🇸 · Dean J. Robinson🇺🇸

   We derive a new flavor symmetry relation for the determination of the weak phase $\beta ={\varphi }_1$ from time-dependent CP asymmetries and $B\to J/\psi P$ decay rates. In this relation, the contributions to $\sin 2\beta$ proportional to $V_{ub}$ are parametrically suppressed compared to the contributions in the $B\to J/\psi K^0$ time-dependent CP asymmetry alone. This relation uses only $SU(3)$ flavor symmetry, and does not require further diagrammatic assumptions. The current data either fluctuate at the $2\sigma$ level from expectations, or may hint at effects of unexpected magnitude from contributions proportional to $V_{ub}$ or from isospin breaking.

   hep-phhep-exPRL(2015)·31 citations
6. 06*

   The Color Discriminant Variable and Scalar Diquarks at the LHC

   R. Sekhar Chivukula🇺🇸 · Pawin Ittisamai🇺🇸 · Kirtimaan Mohan🇺🇸 · Elizabeth H. Simmons🇺🇸

   The LHC is actively searching for narrow dijet resonances corresponding to physics beyond the Standard Model. Among the many resonances that have been postulated (e.g., colored vectors, scalars, and fermions) one that would have a particularly large production rate at the LHC would be a scalar diquark produced in the s-channel via fusion of two valence quarks. In previous work, we introduced a color discriminant variable that distinguishes among various dijet resonances, drawing on measurements of the dijet resonance mass, total decay width and production cross-section. Here, we show that this model-independent method applies well to color-triplet and color-sextet scalar diquarks, distinguishing them clearly from other candidate resonances. We also introduce a more transparent theoretical formulation of the color discriminant variable that highlights its relationship to the branching ratios of the resonance into incoming and outgoing partons and to the properties of those partons. While the original description of the color discriminant variable remains convenient for phenomenological use upon discovery of a new resonance, the new formulation makes it easier to predict the value of the variable for a given class of resonance.

   hep-phPRD(2015)·19 citations
7. 07*

   Field Theory for Zero Sound and Ion Acoustic Wave in Astrophysical Matter

   Gregory Gabadadze🇺🇸 · Rachel A Rosen🇺🇸

   We set up a field theory model to describe the longitudinal low energy modes in high density matter present in white dwarf stars. At the relevant scales, ions -- the nuclei of oxygen, carbon and helium -- are treated as heavy point-like spin-0 charged particles in an effective field theory approach, while the electron dynamics is described by the Dirac Lagrangian at the one-loop level. We show that there always exists a longitudinal gapless mode in the system irrespective whether the ions are in a plasma, crystal, or quantum liquid state. For certain values of the parameters, the gapless mode can be interpreted as a zero sound mode and, for other values, as an ion acoustic wave; we show that the zero sound and ion acoustic wave are complementary to each other. We discuss possible physical consequences of these modes for properties of white dwarfs.

   hep-phhep-thPRD(2016)·0 citations
8. 08*

   Applying Exclusion Likelihoods from LHC Searches to Extended Higgs Sectors

   Philip Bechtle🇩🇪 · Sven Heinemeyer🇪🇸 · Oscar Stal🇸🇪 · Tim Stefaniak🇺🇸 · Georg Weiglein🇩🇪

   LHC searches for non-standard Higgs bosons decaying into tau lepton pairs constitute a sensitive experimental probe for physics beyond the Standard Model (BSM), such as Supersymmetry (SUSY). Recently, the limits obtained from these searches have been presented by the CMS collaboration in a nearly model-independent fashion - as a narrow resonance model - based on the full 8 TeV dataset. In addition to publishing a 95% C.L. exclusion limit, the full likelihood information for the narrow resonance model has been released. This provides valuable information that can be incorporated into global BSM fits. We present a simple algorithm that maps an arbitrary model with multiple neutral Higgs bosons onto the narrow resonance model and derives the corresponding value for the exclusion likelihood from the CMS search. This procedure has been implemented into the public computer code HiggsBounds (version 4.2.0 and higher). We validate our implementation by cross-checking against the official CMS exclusion contours in three Higgs benchmark scenarios in the Minimal Supersymmetric Standard Model (MSSM), and find very good agreement. Going beyond validation, we discuss the combined constraints of the tau tau search and the rate measurements of the SM-like Higgs at 125 GeV in a recently proposed MSSM benchmark scenario, where the lightest Higgs boson obtains SM-like couplings independently of the decoupling of the heavier Higgs states. Technical details for how to access the likelihood information within HiggsBounds are given in the appendix. The program is available at http://higgsbounds.hepforge.org.

   hep-phhep-exEPJC(2015)·333 citations
9. 09*

   A Minimal Non-Supersymmetric $SO(10)$ Model: Gauge Coupling Unification, Proton Decay and Fermion masses

   K. S. Babu🇺🇸 · S. Khan🇺🇸

   We present a minimal renormalizable non-supersymmetric SO(10) grand unified model with a symmetry breaking sector consisting of Higgs fields in the 54_H + 126_H + 10_H representations. This model admits a single intermediate scale associated with Pati-Salam symmetry along with a discrete parity. Spontaneous symmetry breaking, the unification of gauge couplings and proton lifetime estimates are studied in detail in this framework. Including threshold corrections self-consistently, obtained from a full analysis of the Higgs potential, we show that the model is compatible with the current experimental bound on proton lifetime. The model generally predicts an upper bound of few times 10^{35} yrs for proton lifetime, which is not too far from the present Super-Kamiokande limit of \tau_p \gtrsim 1.29 \times 10^{34} yrs. With the help of a Pecci-Quinn symmetry and the resulting axion, the model provides a suitable dark matter candidate while also solving the strong CP problem. The intermediate scale, M_I \approx (10^{13}-10^{14}) GeV which is also the B-L scale, is of the right order for the right-handed neutrino mass which enables a successful description of light neutrino masses and oscillations. The Yukawa sector of the model consists of only two matrices in family space and leads to a predictive scenario for quark and lepton masses and mixings. The branching ratios for proton decay are calculable with the leading modes being p \rightarrow e^+ \pi^0 and p \rightarrow \overline{\nu} \pi^+. Even though the model predicts no new physics within the reach of LHC, the next generation proton decay detectors and axion search experiments have the capability to pass verdict on this minimal scenario.

   hep-phPRD(2015)·94 citations
10. 10*

    Same-sign Higgsino Production at the CERN LHC: How Not to Hunt for Natural Supersymmetry

    Patrick Stengel🇺🇸 · Xerxes Tata🇺🇸

    We examine the prospects for detecting light charged higgsinos that are expected to be a necessary feature of natural SUSY models via $pp\to {\tilde{W}}^{\pm }{\tilde{W}}_1^{\pm }jj+X$ processes arising dominantly from $W^{\pm }{W}^{\pm }$ fusion at LHC13. The signal will be a pair of same-sign leptons ($e$ or $\mu$) in events with two relatively forward, hemispherically-separated jets with a large rapidity gap. We find that even though the higgsinos have a full-strength $SU(2)$ gauge couplings to $W$-bosons, the LHC13 cross section for the production of same sign higgsino pairs is smaller than 0.02 fb over most of the interesting range of natural SUSY parameters, even before leptonic branching fractions of the chargino are included. This cross section is strongly suppressed because the two neutral Majorana higgsinos can be combined into a single Dirac neutralino if the bino and the winos are much heavier than the higgsinos, as is the case in natural SUSY models: in this limit, higgsino couplings to $W$-bosons exhibit an emergent (approximate) $U(1{)}_{\mathrm{ino}}$ global symmetry that suppresses same sign higgsino production by vector boson fusion. We conclude that this channel is not a viable way to search for natural SUSY even at the high luminosity upgrade of the Large Hadron Collider.

    hep-phPRD(2015)·3 citations
11. 11*

    Lepton flavor violation in the BLMSSM

    Shu-Min Zhao🇨🇳 · Tai-Fu Feng🇨🇳 · Hai-Bin Zhang🇨🇳 · Xi-Jie Zhan🇨🇳 · Yin-Jie Zhang🇨🇳 · Ben Yan🇨🇳

    In a supersymmetric extension of the standard model with local gauged baryon and lepton numbers (BLMSSM), there are new sources for lepton flavor violation, because the right-handed neutrinos and new gauginos are introduced. In BLMSSM, we study the charged lepton flavor violating processes $l_j\to l_i+\gamma$ and $l_j\to 3l_i$ in detail. The numerical results show that in some parameter space the branching ratios for charged lepton flavor violating processes can be large enough to be detected in the near future.

    hep-phPRD(2015)·19 citations
12. 12*

    The behavior of the heavy-quarks structure functions at small-$x$

    G. R. Boroun🇮🇷 · B. Rezaei🇮🇷

    The behavior of the charm and bottom structure functions ($F_k^i(x,Q^2)$, i=c,b; k=2,L) at small-$x$ is considered with respect to the hard-Pomeron and saturation models. Having checked that this behavior predicate the heavy flavor reduced cross sections concerning the unshadowed and shadowed corrections. We will show that the effective exponents for the unshadowed and saturation corrections are independent of $x$ and $Q^2$, and also the effective coefficients are dependent to $\ln Q^2$ compared to Donnachie-Landshoff (DL) and color dipole (CD) models.

    hep-phIJMPE(2015)·8 citations
13. 13*

    Complex-mass renormalization in hadronic EFT: applicability at two-loop order

    D. Djukanovic🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · H. Krebs🇩🇪 · U.-G. Meißner🇩🇪

    We discuss the application of the complex-mass scheme to multi-loop diagrams in hadronic effective field theory by considering as an example a two-loop self-energy diagram. We show that the renormalized two-loop diagram satisfies the power counting.

    hep-phEPJA(2015)·14 citations
14. 14*

    Large invisible decay of a Higgs boson to neutrinos

    Osamu Seto🇯🇵

    We show that the standard model (SM)-like Higgs boson may decay into neutrinos with a sizable decay branching ratio in one well-known two Higgs doublet model, so-called neutrinophilic Higgs model. This could happen if the mass of the lighter extra neutral Higgs boson is smaller than one half of the SM-like Higgs boson mass. The definite prediction of this scenario is that the rate of the SM-like Higgs boson decay into diphoton normalized by the SM value is about 0.9. In the case that a neutrino is Majorana particle, a displaced vertex of right-handed neutrino decay would be additionally observed. This example indicates that a large invisible Higgs boson decay could be irrelevant to dark matter.

    hep-phhep-exPRD(2015)·14 citations
15. 15*

    Lepton number asymmetry via inflaton decay in a modified radiative seesaw model

    Shoichi Kashiwase🇯🇵 · Daijiro Suematsu🇯🇵

    We propose a non-thermal scenario for the generation of baryon number asymmetry in a radiative neutrino mass model which is modified to realize inflation at the early Universe. In this scenario, inflaton plays a crucial role in both generation of neutrino masses and lepton number asymmetry. Lepton number asymmetry is firstly generated in the dark matter sector through direct decay of inflaton. It is transferred to the lepton sector via the dark matter annihilation and then converted to the baryon number asymmetry due to the sphaleron interaction. All of the neutrino masses, the baryon number asymmetry and the dark matter are intimately connected to each other through the inflaton.

    hep-phastro-ph.COPLB(2015)·16 citations
16. 16*

    The $\rho (\omega )B^{\ast }(B)$ interaction and states of $J=0,1,2$

    P. Fernandez Soler🇪🇸 · Zhi-Feng Sun🇪🇸 · J. Nieves🇪🇸 · E. Oset🇪🇸

    In this work, we study systems composed of a $\rho /\omega$ and $B^{\ast }$ meson pair. We find three bound states in isospin, spin-parity channels $(1/2,0^{+})$, $(1/2,1^{+})$ and $(1/2,2^{+})$. The state with $J=2$ can be a good candidate for the $B_2^{\ast }(5747)$. We also study the $\rho B$ system, and a bound state with mass $5728$ MeV and width around $20$ MeV is obtained, which can be identified with the $B_1(5721)$ resonance. In the case of $I=3/2$, one obtains repulsion and thus, no exotic (molecular) mesons in this sector are generated in the approach.

    hep-phEPJC(2016)·14 citations
17. 17*

    Totally asymptotically free trinification

    Giulio Maria Pelaggi🇮🇹 · Alessandro Strumia🇮🇹 · Saverio Vignali🇮🇹

    Motivated by new ideas about the Higgs mass naturalness problem, we present realistic TeV-scale extensions of the Standard Model, into the gauge group SU(3)_L x SU(3)_R x SU(3)_c, such that all gauge, Yukawa and quartic couplings can be extrapolated up to infinite energy. Three generations of chiral fermions and Higgses are needed, as well as some extra fermion.

    hep-phJHEP(2015)·49 citations
18. 18*

    On the fate of the Standard Model at finite temperature

    Luigi Delle Rose🇮🇹 · Carlo Marzo🇮🇹 · Alfredo Urbano🇮🇹

    In this paper we revisit and update the computation of thermal corrections to the stability of the electroweak vacuum in the Standard Model. At zero temperature, we make use of the full two-loop effective potential, improved by three-loop beta functions with two-loop matching conditions. At finite temperature, we include one-loop thermal corrections together with resummation of daisy diagrams. We solve numerically---both at zero and finite temperature---the bounce equation, thus providing an accurate description of the thermal tunneling. Assuming a maximum temperature in the early Universe of the order of $10^{18}$ GeV, we find that at finite temperature the instability bound excludes values of the top mass $M_t\gtrsim 173.6$ GeV, with $M_h\simeq 125$ GeV and including uncertainties on the strong coupling. We discuss the validity and temperature-dependence of this bound in the early Universe, with a special focus on the reheating phase after inflation.

    hep-phJHEP(2016)·55 citations
19. 19*

    Identification of a bottom quark-antiquark pair in a single jet with high transverse momentum and its application

    Chunhui Chen🇺🇸

    In this paper we introduce a new approach to identify a bottom quark-antiquark pair inside a single jet with high transverse momentum by using the jet substructure in the center-of-mass frame of the jet. We demonstrate that the method can be used to discriminate the boosted heavy particles decaying to a $b\bar{b}$ final state from QCD jets. Applications to searches for the standard model Higgs boson ($H$) decaying to $b\bar{b}$ when produced in association with a weak vector boson are also discussed.

    hep-phhep-exPRD(2015)·7 citations
20. 20*

    MSSM soft terms from supergravity with gauged R-symmetry in de Sitter vacuum

    Ignatios Antoniadis🇫🇷 · Rob Knoops🇨🇭

    We work out the phenomenology of a model of supersymmetry breaking in the presence of a tiny (tunable) positive cosmological constant, proposed by the authors in arXiv:1403.1534. It utilises a single chiral multiplet with a gauged shift symmetry, that can be identified with the string dilaton (or an appropriate compactification modulus). The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenology that allows to differentiate it from other models of supersymmetry breaking and mediation mechanisms.

    hep-phhep-thNPB(2016)·19 citations
21. 21*

    Prospects for Discovering the Higgs-like Pseudo-Nambu-Goldstone Boson of the Classical Scale Symmetry

    Arsham Farzinnia🇰🇷

    We examine the impact of the expected reach of the LHC and the XENON1T experiments on the parameter space of the minimal classically scale invariant extension of the standard model (SM), where all the mass scales are induced dynamically by means of the Coleman-Weinberg mechanism. In this framework, the SM content is enlarged by the addition of one complex gauge singlet scalar with a scale invariant and $CP$-symmetric potential. The massive pseudoscalar component, protected by the $CP$-symmetry, forms a viable dark matter candidate, and three flavors of the right-handed Majorana neutrinos are included to account for the nonzero masses of the SM neutrinos via the see-saw mechanism. The projected constraints on the parameter space arise by applying the ATLAS heavy Higgs discovery prospects, with an integrated luminosity of 300 and 3000~fb${}^{-1}$ at $\sqrt{s}=14$~TeV, to the pseudo-Nambu-Goldstone boson of the (approximate) scale symmetry, as well as by utilizing the expected reach of the XENON1T direct detection experiment for the discovery of the pseudoscalar dark matter candidate. A null-signal discovery by these future experiments implies that vast regions of the model's parameter space can be thoroughly explored; the combined projections are expected to confine a mixing between the SM and the singlet sector to very small values, while probing the viability of the TeV~scale pseudoscalar's thermal relic abundance as the dominant dark matter component in the Universe. Furthermore, the vacuum stability and triviality requirements of the framework up to the Planck scale are studied and the viable region of the parameter space is identified. The results are summarized in extensive exclusion plots, incorporating additionally the prior theoretical and experimental bounds for comparison.

    hep-phhep-exPRD(2015)·15 citations
22. 22*

    Production of Charged Hadrons in Muon Deep Inelastic Scattering

    Mohammed Sultan Al-Buriahi🇪🇬 · Mohammed Tarek Hussein🇪🇬 · Mohammed Tawfik Ghoneim🇪🇬

    The production of charged hadrons, in muon Deep inelastic scattering (DIS), at light and heavy target is presented. The particles produced by the interaction with Xenon (Xe) is compared with that produced by the interaction with Deuteron (D), to obtain information on cascading process, forward-backward productions, and the rapidity distribution in different bins of the invariant mass of the interacting system W.

    hep-phnucl-exJ.Appl.Math.Phys.(2015)·1 citation
23. 23*

    Transient oscillations in a macroscopic effective theory of the Boltzmann equation

    Dennis Bazow🇺🇸 · Mauricio Martinez🇺🇸 · Ulrich W. Heinz🇺🇸

    A new transient effective theory of the relativistic Boltzmann equation is derived for locally momentum-anisotropic systems. In the expansion of the distribution function around a local "quasi-equilibrium" state a non-hydrodynamic dynamical degree of freedom is introduced at leading order that breaks local momentum isotropy. By replacing the deviation of the distribution function from this quasi-equilibrium state in terms of moments of the leading-order distribution and applying a systematic power counting scheme that orders the non-hydrodynamic modes by their microscopic time scales, a closed set of equations for the dynamical degrees of freedom is obtained. Truncating this set at the level of the slowest non-hydroynamic mode we find that it exhibits transient oscillatory behavior -- a phenomenon previously found only in strongly coupled theories, where it appears to be generic. In weakly coupled systems described by the Boltzmann equation, these transient oscillations depend on the breaking of local momentum isotropy being treated non-perturbatively at leading order in the expansion of the distribution function.

    ↳ nucl-thhep-phPRD(2016)·19 citations
24. 24*

    Low emittance pion beams generation from bright photons and relativistic protons

    L. Serafini🇮🇹 · C. Curatolo🇮🇹 · V. Petrillo🇮🇹

    Present availability of high brilliance photon beams as those produced by X-ray Free Electron Lasers in combination with intense TeV proton beams typical of the Large Hadron Collider makes it possible to conceive the generation of pion beams via photo-production in a highly relativistic Lorentz boosted frame: the main advantage is the low emittance attainable and a TeV-class energy for the generated pions, that may be an interesting option for the production of low emittance muon and neutrino beams. We will describe the kinematics of the two classes of dominant events, i.e. the pion photo-production and the electron/positron pair production, neglecting other small cross-section possible events like Compton and muon pair production. Based on the phase space distributions of the pion and muon beams we will analyze the pion beam brightness achievable in three examples, based on advanced high efficiency high repetition rate FELs coupled to LHC or Future Circular Collider (FCC) proton beams, together with the study of a possible small scale demonstrator based on a Compton Source coupled to a Super Proton Synchrotron (SPS) proton beam.

    ↳ physics.acc-phhep-ph7 citations
25. 25*

    Diagonal and off-diagonal quark number susceptibilities at high temperatures

    H.-T. Ding🇨🇳 · Swagato Mukherjee🇺🇸 · H. Ohno🇺🇸 · P. Petreczky🇺🇸 · H.-P. Schadler🇦🇹

    We present continuum extrapolated lattice QCD results for up to fourth-order diagonal and off-diagonal quark number susceptibilities in the high temperature region of 300-700 MeV. Lattice QCD calculations are performed using 2+1 flavors of highly improved staggered quarks with nearly physical quark masses and at four different lattice spacings. Comparisons of our results with recent weak coupling perturbative calculations yield reasonably good agreements for the entire temperature range.

    ↳ hep-lathep-phnucl-thPRD(2015)·126 citations
26. 26*

    Beyond six parameters: extending $\Lambda$CDM

    Eleonora Di Valentino🇫🇷 · Alessandro Melchiorri🇮🇹 · Joseph Silk🇫🇷

    Cosmological constraints are usually derived under the assumption of a $6$ parameters $\Lambda$-CDM theoretical framework or simple one-parameter extensions. In this paper we present, for the first time, cosmological constraints in a significantly extended scenario, varying up to $12$ cosmological parameters simultaneously, including the sum of neutrino masses, the neutrino effective number, the dark energy equation of state, the gravitational waves background and the running of the spectral index of primordial perturbations. Using the latest Planck 2015 data release (with polarization) we found no significant indication for extensions to the standard $\Lambda$-CDM scenario, with the notable exception of the angular power spectrum lensing amplitude, $A_{\mathrm{lens}}$ that is larger than the expected value at more than two standard deviations even when combining the Planck data with BAO and supernovae type Ia external datasets. In our extended cosmological framework, we find that a combined Planck+BAO analysis constrains the value of the r.m.s. density fluctuation parameter to ${\sigma }_8=0.781_{-0.063}^{+0.065}$ at $95\%$ c.l., helping to relieve the possible tensions with the CFHTlenS cosmic shear survey. We also find a lower value for the reionization optical depth $\tau =0.058_{-0.043}^{+0.040}$ at $95$ \% c.l. respect to the one derived under the assumption of $\Lambda$-CDM. The scalar spectral index $n_S$ is now compatible with a Harrison-Zeldovich spectrum to within $2.5$ standard deviations. Combining the Planck dataset with the HST prior on the Hubble constant provides a value for the equation of state $w<-1$ at more than two standard deviations while the neutrino effective number is fully compatible with the expectations of the standard three neutrino framework.

    ↳ astro-ph.COgr-qchep-phPRD(2015)·120 citations
27. 27*

    A Model Independent Approach to (p)Reheating

    Ogan Özsoy🇺🇸 · Gizem Sengor🇺🇸 · Kuver Sinha🇺🇸 · Scott Watson🇺🇸

    In this note we propose a model independent framework for inflationary (p)reheating. Our approach is analogous to the Effective Field Theory of Inflation, however here the inflaton oscillations provide an additional source of (discrete) symmetry breaking. Using the Goldstone field that non-linearly realizes time diffeormorphism invariance we construct a model independent action for both the inflaton and reheating sectors. Utilizing the hierarchy of scales present during the reheating process we are able to recover known results in the literature in a simpler fashion, including the presence of oscillations in the primordial power spectrum. We also construct a class of models where the shift symmetry of the inflaton is preserved during reheating, which helps alleviate past criticisms of (p)reheating in models of Natural Inflation. Extensions of our framework suggest the possibility of analytically investigating non-linear effects (such as rescattering and back-reaction) during thermalization without resorting to lattice methods. By construction, the EFT relates the strength of many of these interactions to other operators in the theory, including those responsible for the efficiency of (p)reheating. We conclude with a discussion of the limitations and challenges for our approach.

    ↳ hep-thastro-ph.COhep-ph18 citations
28. 28*

    Sterile neutrino dark matter: A tale of weak interactions in the strong coupling epoch

    Tejaswi Venumadhav🇺🇸 · Francis-Yan Cyr-Racine🇺🇸 · Kevork N. Abazajian🇺🇸 · Christopher M. Hirata🇺🇸

    We perform a detailed study of the weak interactions of standard model neutrinos with the primordial plasma and their effect on the resonant production of sterile neutrino dark matter. Motivated by issues in cosmological structure formation on small scales, and reported X-ray signals that could be due to sterile neutrino decay, we consider $7$ keV-scale sterile neutrinos. Oscillation-driven production of such sterile neutrinos occurs at temperatures $T\gtrsim 100$ MeV, where we study two significant effects of weakly charged species in the primordial plasma: (1) the redistribution of an input lepton asymmetry; (2) the opacity for active neutrinos. We calculate the redistribution analytically above and below the quark-hadron transition, and match with lattice QCD calculations through the transition. We estimate opacities due to tree level processes involving leptons and quarks above the quark-hadron transition, and the most important mesons below the transition. We report final sterile neutrino dark matter phase space densities that are significantly influenced by these effects, and yet relatively robust to remaining uncertainties in the nature of the quark-hadron transition. We also provide transfer functions for cosmological density fluctuations with cutoffs at $k\simeq 10h{\mathrm{Mpc}}^{-1}$, that are relevant to galactic structure formation.

    ↳ astro-ph.COhep-phPRD(2016)·143 citations
29. 29*

    Large scale structure from viscous dark matter

    Diego Blas🇨🇭 · Stefan Floerchinger🇨🇭 · Mathias Garny🇨🇭 · Nikolaos Tetradis🇬🇷 · Urs Achim Wiedemann🇨🇭

    Cosmological perturbations of sufficiently long wavelength admit a fluid dynamic description. We consider modes with wavevectors below a scale $k_m$ for which the dynamics is only mildly non-linear. The leading effect of modes above that scale can be accounted for by effective non-equilibrium viscosity and pressure terms. For mildly non-linear scales, these mainly arise from momentum transport within the ideal and cold but inhomogeneous fluid, while momentum transport due to more microscopic degrees of freedom is suppressed. As a consequence, concrete expressions with no free parameters, except the matching scale $k_m$, can be derived from matching evolution equations to standard cosmological perturbation theory. Two-loop calculations of the matter power spectrum in the viscous theory lead to excellent agreement with $N$-body simulations up to scales $k=0.2h/$Mpc. The convergence properties in the ultraviolet are better than for standard perturbation theory and the results are robust with respect to variations of the matching scale.

    ↳ astro-ph.COhep-phJCAP(2015)·78 citations
30. 30*

    Constraining heavy quark energy loss using $B$ and $D$ meson measurements in heavy ion collision at RHIC and LHC energies

    Kapil Saraswat🇮🇳 · Prashant Shukla🇮🇳 · Venktesh Singh🇮🇳

    In this work, we calculate energy loss of heavy quark (charm and bottom) due to elastic collisions and gluon radiation in hot/dense medium. The collisional energy loss has been obtained using QCD calculations. The radiative energy loss is calculated using reaction operator formalism and generalized dead cone approach. We rederive the energy loss expression using same assumptions as generalized dead cone approach but obtain slightly different results. We also improve the model employed to calculate path length and the system evolution. The nuclear modification factors $R_{AA}$ including shadowing and energy loss are evaluated for $B$ and $D$ mesons and are compared with the measurements in PbPb collision at $\sqrt{s_{NN}}$ = 2.76 TeV and with the D meson and Heavy flavour (HF) electrons measurements in AuAu collision at $\sqrt{s_{NN}}$ = 200 GeV. The radiative energy loss calculated by reaction operator formalism added with collisional energy loss describes the RHIC HF electron suppression in high $p_T$ range. It also describes the LHC measurement of $B$ meson suppression but overestimates the suppression of $D$ meson. The radiative energy loss from generalized dead cone approach describes the charm suppression at both RHIC as well as LHC energies and requires energy loss due to collisions to be added in order to describe the bottom suppression at LHC.

    ↳ nucl-thhep-phnucl-exNPA(2015)·23 citations
31. 31*

    Study of the diffuse gamma-ray emission from the Galactic plane with ARGO-YBJ

    B. Bartoli🇮🇹 · P. Bernardini🇮🇹 · X.J. Bi🇨🇳 · P. Branchini🇮🇹 · A. Budano🇮🇹 · P. Camarri🇮🇹 · Z. Cao🇨🇳 · R. Cardarelli🇮🇹 · S. Catalanotti🇮🇹 · S.Z. Chen🇨🇳 · T.L. Chen🇨🇳 · P. Creti🇮🇹 and 69 other authors

    The events recorded by ARGO-YBJ in more than five years of data collection have been analyzed to determine the diffuse gamma-ray emission in the Galactic plane at Galactic longitudes 25{\deg} < l < 100{\deg} and Galactic latitudes . The energy range covered by this analysis, from ~350 GeV to ~2 TeV, allows the connection of the region explored by Fermi with the multi-TeV measurements carried out by Milagro. Our analysis has been focused on two selected regions of the Galactic plane, i.e., 40{\deg} < l < 100{\deg} and 65{\deg} < l < 85{\deg} (the Cygnus region), where Milagro observed an excess with respect to the predictions of current models. Great care has been taken in order to mask the most intense gamma-ray sources, including the TeV counterpart of the Cygnus cocoon recently identified by ARGO-YBJ, and to remove residual contributions. The ARGO-YBJ results do not show any excess at sub-TeV energies corresponding to the excess found by Milagro, and are consistent with the predictions of the Fermi model for the diffuse Galactic emission. From the measured energy distribution we derive spectral indices and the differential flux at 1 TeV of the diffuse gamma-ray emission in the sky regions investigated.

    ↳ astro-ph.IMastro-ph.HEhep-phApJ·130 citations
32. 32*

    Minkowski 3-forms, Flux String Vacua, Axion Stability and Naturalness

    Sjoerd Bielleman🇪🇸 · Luis E. Ibanez🇪🇸 · Irene Valenzuela🇪🇸

    We discuss the role of Minkowski 3-forms in flux string vacua. In these vacua all internal closed string fluxes are in one to one correspondence with quantized Minkowski 4-forms. By performing a dimensional reduction of the $D=10$ Type II supergravity actions we find that the 4-forms act as auxiliary fields of the Kahler and complex structure moduli in the effective action. We show that all the RR and NS axion dependence of the flux scalar potential appears through the said 4-forms. Gauge invariance of these forms then severely restricts the structure of the axion scalar potentials. Combined with duality symmetries it suggests that all perturbative corrections to the leading axion scalar potential $V_0$ should appear as an expansion in powers of $V_0$ itself. These facts could have an important effect e.g. on the inflaton models based on F-term axion monodromy. We also suggest that the involved multi-branched structure of string vacua provides for a new way to maintain interacting scalar masses stable against perturbative corrections.

    ↳ hep-thhep-phJHEP(2015)·105 citations
33. 33*

    Split symmetries

    Wilfried Buchmuller🇩🇪 · Markus Dierigl🇩🇪 · Fabian Ruehle🇩🇪 · Julian Schweizer🇩🇪

    We consider six-dimensional supergravity with gauge group $SO(10)\times U(1{)}_A$, compactified on the orbifold $T^2/{\mathbb{Z}}_2$. Three quark-lepton generations arise as zero modes of a bulk $16$-plet due to magnetic flux of the anomalous $U(1{)}_A$. Boundary conditions at the four fixed points break $SO(10)$ to subgroups whose intersection is the Standard Model gauge group. The gauge and Higgs sector consist of "split" $SO(10)$ multiplets. As consequence of the $U(1{)}_A$ flux, squarks and sleptons are much heavier than gauge bosons, Higgs bosons, gauginos and higgsinos. We thus obtain a picture similar to "split supersymmetry." The flavor structure of the quark and lepton mass matrices is determined by the symmetry breaking at the orbifold fixed points.

    ↳ hep-thhep-phPLB(2015)·31 citations
34. 34*

    On the algebraic structure of rotationally invariant two-dimensional Hamiltonians on the noncommutative phase space

    H. Falomir🇦🇷 · P.A.G. Pisani🇦🇷 · F. Vega🇦🇷 · D. Cárcamo🇨🇱 · F. Méndez🇨🇱 · M. Loewe🇿🇦

    We study two-dimensional Hamiltonians in phase space with noncommutativity both in coordinates and momenta. We consider the generator of rotations on the noncommutative plane and the Lie algebra generated by Hermitian rotationally invariant quadratic forms of noncommutative dynamical variables. We show that two quantum phases are possible, characterized by the Lie algebras $sl(2,\mathbb{R})$ or $su(2)$ according to the relation between the noncommutativity parameters, with the rotation generator related with the Casimir operator. From this algebraic perspective, we analyze the spectrum of some simple models with nonrelativistic rotationally invariant Hamiltonians in this noncommutative phase space, as the isotropic harmonic oscillator, the Landau problem and the cylindrical well potential. PACS: 03.65.-w; 03.65.Fd MSC: 81R05; 20C35; 22E70

    ↳ math-phhep-phhep-thmath.MP+1J.Phys.A(2016)·12 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.