Mon·Oct 19, 2015Monday·October 19, 2015

1. 01*

   Probe of new light Higgs bosons from bottomonium chi_{b0} decay

   Stephen Godfrey🇨🇦 · Heather E. Logan (Carleton U.)🇨🇦

   We calculate the branching ratios of chi_{b0} --> tau+ tau- via an s-channel Higgs boson and estimate the sensitivity to this process from Upsilon --> gamma chi_{b0} --> gamma tau+ tau-. We show that future running at the Upsilon(3S) at a very high luminosity super B factory can put significant constraints on the Type-II two-Higgs-doublet model when the discovered 125 GeV Higgs boson is the heavier of the two CP-even scalars.

   hep-phhep-exPRD(2016)·11 citations
2. 02*

   Magnetic response of baryon properties in a skyrmion model

   Bing-Ran He🇯🇵

   An axially symmetric ansatz is proposed to investigate the properties of baryon in a uniform magnetic field. The baryon number is shown to be conserved, while the baryon shape is stretched along the magnetic field. It is found that with increasing magnetic field strength, the static mass of the baryon first decreases and then increases, while the size of the baryon first increases and then decreases. Finally, in the core part of the magnetar, the equation of state strongly depends on the magnetic field, which modifies the mass limit of the magnetar.

   hep-phhep-latnucl-thPRD(2015)·16 citations
3. 03*

   Analysis of the $h,H,A\to \tau \mu$ decays induced from SUSY loops within the Mass Insertion Approximation

   E. Arganda🇪🇸 · M.J. Herrero🇪🇸 · R. Morales🇦🇷 · A. Szynkman🇦🇷

   In this paper we study the lepton favor violating decay channels of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model into a lepton and an anti-lepton of different flavor. We work in the context of the most general flavor mixing scenario in the slepton sector, in contrast to the minimal flavor violation assumption more frequently used. Our analytic computation is a one-loop diagrammatic one, but in contrast to the full one-loop computation which is usually referred to the physical slepton mass basis, we use here instead the Mass Insertion Approximation (MIA) which uses the electroweak interaction slepton basis and treats perturbatively the mass insertions changing slepton flavor. By performing an expansion in powers of the external momenta in the relevant form factors, we will be able to separate explicitly in the analytic results the leading non-decoupling (constant at asymptotically large sparticle masses) and the next to leading decoupling contributions (decreasing with the sparticle masses). Our final aim is to provide a set of simple analytic formulas for the form factors and the associated effective vertices, that we think may be very useful for future phenomenological studies of the lepton flavor violating Higgs boson decays, and for their comparison with data. The accuracy of the numerical results obtained with the MIA are also analyzed and discussed here in comparison with the full one-loop results. Our most optimistic numerical estimates for the three neutral Higgs boson decays channels into $\tau$ and $\mu$ leptons, searching for their maximum rates that are allowed by present constraints from $\tau \to \mu \gamma$ data and beyond Standard Model Higgs boson searches at the LHC, are also included.

   hep-phhep-exJHEP(2016)·65 citations
4. 04*

   Completing constrained flavor violation: lepton masses, neutrinos and leptogenesis

   James M. Cline🇨🇦 · Alfonso Diaz-Furlong🇨🇦 · Jing Ren🇨🇦

   Constrained flavor violation is a recent proposal for predicting the down-quark Yukawa matrix in terms of those for up quarks and charged leptons. We study the viability of CFV with respect to its predictions for the lepton mass ratios, showing that this remains a challenge, and suggest some possible means for improving this shortcoming. We then extend CFV to include neutrinos, and show that it leads to interesting predictions for hierachical heavy neutrinos, and leptogenesis dominated by decays of the second heaviest one ("N2 leptogenesis"), as well as the possibility of low-scale leptoquark-mediated exotic decays.

   hep-phastro-ph.COPRD(2016)·7 citations
5. 05*

   Beyond Minimal Lepton Flavored Dark Matter

   Mu-Chun Chen🇺🇸 · Jinrui Huang🇺🇸 · Volodymyr Takhistov🇺🇸

   We consider a class of flavored dark matter (DM) theories where dark matter interacts with the Standard Model lepton fields at the renormalizable level. We allow for a general coupling matrix between the dark matter and leptons whose structure is beyond the one permitted by the minimal flavor violation (MFV) assumption. It is assumed that this is the only new source of flavor violation in addition to the Standard Model (SM) Yukawa interactions. The setup can be described by augmenting the SM flavor symmetry by an additional $\mathrm{SU}(3{)}_{\chi }$, under which the dark matter $\chi$ transforms. This framework is especially phenomenologically rich, due to possible novel flavor-changing interactions which are not present within the more restrictive MFV framework. As a representative case study of this setting, which we call "beyond MFV" (BMFV), we consider Dirac fermion dark matter which transforms as a singlet under the SM gauge group and a triplet under $\mathrm{SU}(3{)}_{\chi }$. The DM fermion couples to the SM lepton sector through a scalar mediator $\varphi$. Unlike the case of quark-flavored DM, we show that there is no ${\mathbb{Z}}_3$ symmetry within either the MFV or BMFV settings which automatically stabilizes the lepton-flavored DM. We discuss constraints on this setup from flavor-changing processes, DM relic abundance as well as direct and indirect detections. We find that relatively large flavor-changing couplings are possible, while the dark matter mass is still within the phenomenologically interesting region below the TeV scale. Collider signatures which can be potentially searched for at the lepton and hadron colliders are discussed. Finally, we discuss the implications for decaying dark matter, which can appear if an additional stabilizing symmetry is not imposed.

   hep-phhep-exJHEP(2016)·46 citations
6. 06*

   On the rapidity dependence of the average transverse momentum in hadronic collisions

   F. O. Durães🇧🇷 · A. V. Giannini🇧🇷 · V. P. Goncalves🇧🇷 · F. S. Navarra🇧🇷

   The energy and rapidity dependence of the average transverse momentum $⟨p_T⟩$ in $pp$ and $pA$ collisions at RHIC and LHC energies are estimated using the Colour Glass Condensate (CGC) formalism. We update previous predictions for the $p_T$ - spectra using the hybrid formalism of the CGC approach and two phenomenological models for the dipole - target scattering amplitude. We demonstrate that these models are able to describe the RHIC and LHC data for the hadron production in $pp$, $dAu$ and $pPb$ collisions at $p_T\le 20$ GeV. Moreover, we present our predictions for $⟨p_T⟩$ and demonstrate that the ratio $⟨p_T(y)⟩/⟨p_T(y=0)⟩$ decreases with the rapidity and has a behaviour similar to that predicted by hydrodynamical calculations.

   hep-phhep-exnucl-exnucl-thPRC(2016)·18 citations
7. 07*

   Reconstruction of the standard model with classical conformal invariance in noncommutative geometry

   Masaki J.S. Yang🇯🇵

   In this paper, we derive the standard model with classical conformal invariance from the Yang--Mills--Higgs model in noncommutative geometry (NCG). In the ordinary context of the NCG, the {\it distance matrix} $M_{nm}$ which corresponds to the vacuum expectation value of Higgs fields is taken to be finite. However, since $M_{nm}$ is arbitrary in this formulation, we can take all $M_{nm}$ to be zero. In the original composite scheme, the Higgs field itself vanishes with the condition $M_{nm}=0$. Then, we adopt the elemental scheme, in which the gauge and the Higgs bosons are regarded as elemental fields. By these assumptions, all scalars do not have vevs at tree level. The symmetry breaking mechanism will be implemented by the Coleman--Weinberg mechanism. As a result, we show a possibility to solve the hierarchy problem in the context of NCG. Unfortunately, the Coleman--Weinberg mechanism does not work in the SM Higgs sector, because the Coleman--Weinberg effective potential becomes unbounded from below for $m_t>m_Z$. However, viable models can be possible by proper extensions.

   hep-phhep-thPTEP(2016)·3 citations
8. 08*

   Looking for quark saturation in proton and nuclei

   Wei Zhu🇨🇳 · Rong Wang🇨🇳 · Jianhong Ruan🇨🇳

   The quark saturation behavior at low $Q^2$ is shown in a numeric solution of the DGLAP equation with parton recombination corrections, which resembles the widely discussed JIMWLK saturation of gluons. Our calculation suggests that the partonic saturation can be interpreted as a dynamical balance between the splitting and the fusion processes of partons, without any other condensation mechanisms added. The nuclear shadowing saturation at small $x$ resulted from the proposed quark saturation is also discussed.

   hep-phIJMPE(2017)·1 citation
9. 09*

   Improved bounds on the heavy neutrino productions at the LHC

   Arindam Das🇺🇸 · Nobuchika Okada🇺🇸

   The Majorana neutrino in type-I seesaw and the pseudo-Dirac neutrinos in the inverse seesaw can have sizable mixings with the light neutrinos in the standard model (SM), through which the heavy neutrinos can be produced at the Large Hadron Collider (LHC). In producing the heavy neutrinos we study a variety of initial states such as quark-quark, quark-gluon and gluon-gluon as well as photon mediated processes. For the Majorana heavy neutrino production we consider same-sign di-lepton plus di-jet as the signal events. Using the recent ATLAS and CMS data at $\sqrt{s}=$ 8 TeV with 20.3 fb${}^{-1}$ and 19.7 fb${}^{-1}$ luminosities, respectively, we obtain direct upper bounds on the light-heavy neutrino mixing angles. For the pseudo-Dirac heavy neutrino production we consider the final sate with tri-lepton plus missing energy as the signal events. Using the recent anomalous multi-lepton search by CMS at $\sqrt{s}=$ 8 TeV with 19.5 fb${}^{-1}$ luminosity we obtain upper bounds on the mixing angles. Taking the varieties of initial states into account, the previously obtained upper bounds on the mixing angles have been improved. We scale our results at the 8 TeV LHC to obtain a prospective search reach at the 14 TeV LHC with high luminosities.

   hep-phhep-exPRD(2016)·129 citations
10. 10*

    A minimal seesaw model with mu-tau symmetry

    Darius Jurciukonis🇱🇹 · Thomas Gajdosik🇱🇹 · Andrius Juodagalvis🇱🇹

    We analyse a flavour model for a lepton sector which is based on type I seesaw mechanism, a Z_2 symmetry for lepton flavours, a mu-tau interchange symmetry and a CP symmetry. This model fits well the data of neutrino mass squared differences and oscillation angles. The model predicts an overall neutrino mass scale for normal and inverted neutrino mass hierarchy and the effective mass m_beta, which is used in the neutrinoless double beta decay.

    hep-phPoS(2015)·0 citations
11. 11*

    Parametric resonance after hilltop inflation caused by an inhomogeneous inflaton field

    Stefan Antusch🇨🇭 · Francesco Cefala🇨🇭 · David Nolde🇨🇭 · Stefano Orani🇨🇭

    We study preheating after hilltop inflation where the inflaton couples to another scalar field, e.g. a right-handed sneutrino, which provides a mechanism for generating the correct initial conditions for inflation and also a decay channel for the inflaton that allows for reheating and non-thermal leptogenesis. In the presence of such a coupling, we find that after the phases of tachyonic preheating and tachyonic oscillations, during which the inflaton field becomes inhomogeneous, there can be a subsequent preheating phase where the fluctuations of the other field get resonantly enhanced, from initial vacuum fluctuations up to amplitudes of the same order (and even larger) as the ones of the inflaton field. This resonant enhancement differs from the usual parametric resonance as the inflaton field is inhomogeneous at the time the enhancement takes place. We study this effect using lattice simulations as well as semi-analytically with a generalized Floquet analysis for inhomogeneous background fields.

    hep-phastro-ph.COhep-thJCAP(2016)·29 citations
12. 12*

    Colour Reconnection - Models and Tests

    Jesper R. Christiansen🇸🇪

    Recent progress on colour reconnection within the Pythia framework is presented. A new model is introduced, based on the SU(3) structure of QCD and a minimization of the potential string energy. The inclusion of the epsilon structure of SU(3) gives a new baryon production mechanism and makes it possible simultaneously to describe hyperon production at both $e^{+}{e}^{-}$ and pp colliders. Finally, predictions for $e^{+}{e}^{-}$ colliders, both past and potential future ones, are presented.

    hep-phPoS(2015)·4 citations
13. 13*

    Naughty or Nice? The Role of the `N' in the Natural NMSSM for the LHC

    Jong Soo Kim🇪🇸 · Daniel Schmeier🇩🇪 · Jamie Tattersall🇩🇪

    In this work, we present mass limits on gluinos and stops in a natural Next-to-Minimal Supersymmetric Standard Model (NMSSM) with a singlino as the lightest supersymmetric particle. Motivated by naturalness, we consider spectra with light higgsinos, sub-TeV third generation sparticles and gluinos well below the multi-TeV regime while the electroweak gauginos, the sleptons and the first and second generation squarks are decoupled. We check that our natural supersymmetry spectra satisfy all electroweak precision observables and flavour measurements as well as theoretical constraints. By reinterpreting the results from the 8 TeV ATLAS supersymmetry searches we present the 95% CL exclusion limits on the model. The results show that the presence of a singlino LSP can lengthen decay chains and soften the final state particle energies. Whilst this does reduce the strength of the bounds in some areas of parameter space, the LHC still displays good sensitivity to the model.

    hep-phPRD(2016)·16 citations
14. 14*

    Leptogluons in dilepton production at LHC

    Tomasz Jeliński🇵🇱 · Dmitry Zhuridov🇵🇱

    In the composite models with colored substructure of the fermions the color singlet leptons are accompanied by a composite color octet partners, which are known as leptogluons. We consider the effect of leptogluons in the dilepton production at the LHC and show that in the reachable parameter range this effect is typically dominated by t-channel leptogluon exchange (indirect channel). We show that this channel alone can give a sizable contribution to the dimuon production at the LHC for TeV scale values of the invariant mass of the muon-antimuon pairs.

    hep-phActa Phys.Polon.B(2015)·10 citations
15. 15*

    FRG Approach to Nuclear Matter at Extreme Conditions

    Péter Pósfay🇭🇺 · Gergely Gábor Barnaföldi🇭🇺 · Antal Jakovác🇭🇺

    Functional renormalization group (FRG) is an exact method for taking into account the effect of quantum fluctuations in the effective action of the system. The FRG method applied to effective theories of nuclear matter yields equation of state which incorporates quantum fluctuations of the fields. Using the local potential approximation (LPA) the equation of state for Walecka-type models of nuclear matter under extreme conditions could be determined. These models can be tested by solving the corresponding Tolman--Oppenheimer--Volkov (TOV) equations and investigating the properties (mass and radius) of the corresponding compact star models. Here, we present the first steps on this way, we obtained a Maxwell construction within the FRG-based framework using a Walecka-type Lagrangian.

    hep-phastro-ph.HEnucl-thPoS(2015)·3 citations
16. 16*

    The O(N)-model within the Phi-derivable expansion to order lambda^2: on the existence, UV and IR sensitivity of the solutions to self-consistent equations

    Gergely Markó🇭🇺 · Urko Reinosa🇫🇷 · Zsolt Szép🇭🇺

    We discuss various aspects of the O(N)-model in the vacuum and at finite temperature within the Phi-derivable expansion scheme to order lambda^2. In continuation to an earlier work, we look for a physical parametrization in the N=4 case that allows to accommodate the lightest mesons. Using zero-momentum curvature masses to approximate the physical masses, we find that, in the parameter range where a relatively large sigma mass is obtained, the scale of the Landau pole is lower compared to that obtained in the two-loop truncation. This jeopardizes the insensitivity of the observables to the ultraviolet regulator and could hinder the predictivity of the model. Both in the N=1 and N=4 cases, we also find that, when approaching the chiral limit, the (iterative) solution to the Phi-derivable equations is lost in an interval around the would-be transition temperature. In particular, it is not possible to conclude at this order of truncation on the order of the transition in the chiral limit. Because the same issue could be present in other approaches, we investigate it thoroughly by considering a localized version of the Phi-derivable equations, whose solution displays the same qualitative features, but allows for a more analytical understanding of the problem. In particular, our analysis reveals the existence of unphysical branches of solutions which can coalesce with the physical one at some temperatures, with the effect of opening up a gap in the admissible values for the condensate. Depending on its rate of growth with the temperature, this gap can eventually engulf the physical solution.

    hep-phPRD(2015)·23 citations
17. 17*

    Heavy hybrids in pNRQCD

    Jaume Tarrús Castellà🇩🇪

    We report on the calculation of the Quarkonium Hybrid masses for the $cg\bar{c}$, $bg\bar{c}$ and $bg\bar{b}$ systems~\cite{hbrpaper}. A QCD analog of the Born-Oppenheimer approximation including the $\Lambda$--doubling terms has been used. The gluonic static energies are obtained combining the short range description from potential non--relativistic QCD (pNRQCD) and lattice QCD calculations. The effect $\Lambda$--doubling terms is to mix the contributions of the static energies to the hybrid states leading to the break of the degeneracy between spin symmetry multiplets with opposite parity. The spin symmetry multiplets with mixed contributions from different static energies have a lower mass with respect to the parity opposite that remains without mixed contributions. We compare with direct lattice calculations and discuss several experimental candidates.

    hep-phhep-exhep-latAIP Conf.Proc.(2016)·1 citation
18. 18*

    Two-loop-induced neutrino masses: A model-independent perspective

    D. Aristizabal Sierra🇧🇪

    We discuss Majorana neutrino mass generation mechanisms at the two-loop order. After briefly reviewing the systematic classification of one-loop realizations, we then focus on a general two-loop classification scheme which provides a model-independent catalog for neutrino mass models at the two-loop order

    hep-phPoS(2015)·2 citations
19. 19*

    On effective Chern-Simons Term induced by a Local CPT-Violating Coupling using ${\gamma }_5$ in Dimensional Regularization

    Ruggero Ferrari🇮🇹 · Mario Raciti🇮🇹

    We resume a long-standing, yet not forgotten, debate on whether a Chern-Simons birefringence can be generated by a local term $b_{\mu }\bar{\psi }{\gamma }^{\mu }{\gamma }_5\psi$ in the Lagrangian (where $b_{\mu }$ are constants). In the present paper we implement a new way of managing ${\gamma }_5$ in dimensional regularization. Gauge invariance in the underlying theory (QED) is enforced by this choice of defining divergent amplitudes. We investigate the singular behavior of the vector meson two-point-function around the $m^2=0$ and $p^2=0$ point. We find that the coefficient of the effective Chern-Simons can be finite or zero. It depends on how one takes the limits: they cannot be interchanged due to the associate change of symmetry. For $m^2=0$ we evaluate also the self-mass of the photon at the second orderin $b_{\mu }$. We find zero.

    ↳ hep-thastro-ph.COhep-phnucl-th2 citations
20. 20*

    Putting Things Back Where They Belong: Tracing Cosmic-Ray Injection with H2

    Eric Carlson🇺🇸 · Tim Linden🇺🇸 · Stefano Profumo🇺🇸

    At present, all physical models of diffuse Galactic gamma-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H2-rich regions host significant star formation and numerous supernova remnants, the morphology of observed H2 gas should also provide a physically motivated, high-resolution tracer for cosmic-ray injection. We assess the impact of utilizing H2 as a tracer for cosmic-ray injection on models of diffuse Galactic gamma-ray emission. We employ state-of-the-art 3D particle diffusion and gas density models, along with a physical model for the star-formation rate based on global Schmidt laws. Allowing a fraction, f_H2, of cosmic-ray sources to trace the observed H2 density, we find that a theoretically well-motivated value f_H2 ~ 0.20 -- 0.25 (i) provides a significantly better global fit to the diffuse Galactic gamma-ray sky and (ii) highly suppresses the intensity of the residual gamma-ray emission from the Galactic center region. Specifically, in models utilizing our best global fit values of f_H2 ~ 0.20 -- 0.25, the spectrum of the galactic center gamma-ray excess is drastically affected, and the morphology of the excess becomes inconsistent with predictions for dark matter annihilation.

    ↳ astro-ph.HEastro-ph.GAhep-phPRL(2016)·45 citations
21. 21*

    Theory of Quantum Gravity Beyond Einstein and Space-time Dynamics with Quantum Inflation

    Yue-Liang Wu🇨🇳

    In this talk, I present a theory of quantum gravity beyond Einstein. The theory is established based on spinnic and scaling gauge symmetries by treating the gravitational force on the same footing as the electroweak and strong forces. A bi-frame space-time is initiated to describe the laws of nature. One frame space-time is a globally flat coordinate Minkowski space-time that acts as an inertial reference frame for the motions of fields, the other is a locally flat non-coordinate Gravifield space-time that functions as an interaction representation frame for the degrees of freedom of fields. The Gravifield is sided on both the globally flat coordinate space-time and locally flat non-coordinate space-time and characterizes the gravitational force. Instead of the principle of general coordinate invariance in Einstein theory of general relativity, some underlying principles with the postulates of coordinate independence and gauge invariance are motivated to establish the theory of quantum gravity. When transmuting the Gravifield basis into the coordinate basis in Minkowski space-time, it enables us to obtain equations of motion for all quantum fields and derive basic conservation laws for all symmetries. When the spinnic and scaling gauge symmetries are broken down to a background structure that possesses the global Lorentz and scaling symmetries, we arrive at a Lorentz invariant and conformally flat background Gravifield space-time that is characterized by a cosmic vector with a non-zero cosmological mass scale. We also obtain the massless graviton and massive spinnon. We show a mechanism for quantum inflation caused by the quantum loop contributions. The Einstein theory of general relativity is expected to be an effective low energy theory. Two types of gravity equation are resulted.

    ↳ hep-thgr-qchep-phInt.J.Mod.Phys.A(2015)·12 citations
22. 22*

    Tachyon field non-minimally coupled to massive neutrino matter

    Safia Ahmad🇮🇳 · Nurgissa Myrzakulov🇰🇿 · R. Myrzakulov🇰🇿

    In this paper, we consider rolling tachyon, with steep run-away type of potentials non-minimally coupled to massive neutrino matter. The coupling dynamically builds up at late times as neutrino matter turns non-relativistic. In case of scaling and string inspired potentials, we have shown that non-minimal coupling leads to minimum in the field potential. Given a suitable choice of model parameters, it is shown to give rise to late-time acceleration with the desired equation of state.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2016)·7 citations
23. 23*

    Dynamical Emergence of the Universe into the False Vacuum

    Johann Rafelski🇺🇸 · Jeremiah Birrell🇺🇸

    We study how the hot Universe evolves and acquires the prevailing vacuum state, demonstrating that in specific conditions which are believed to apply, the Universe becomes frozen into the state with the smallest value of Higgs vacuum field $v=⟨h⟩$, even if this is not the state of lowest energy. This supports the false vacuum dark energy $\Lambda$-model. Under several likely hypotheses we determine the temperature in the evolution of the Universe at which two vacuua $v_1,v_2$ can swap between being true and false. We evaluate the dynamical surface pressure on domain walls between low and high mass vaccua due to the presence of matter and show that the low mass state remains the preferred vacuum of the Universe.

    ↳ astro-ph.COgr-qchep-phJCAP(2015)·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.