Mon·Mar 14, 2016Monday·March 14, 2016

1. 01*

   Probing New Physics Scales from Higgs and Electroweak Observables at $e^{+}{e}^{-}$ Higgs Factory

   Shao-Feng Ge🇩🇪 · Hong-Jian He🇨🇳 · Rui-Qing Xiao🇺🇸

   New physics beyond the standard model (SM) can be model-independently formulated via dimension-6 effective operators, whose coefficients (cutoffs) characterize the scales of new physics. We study the probe of new physics scales from the electroweak precision observables (EWPO) and the Higgs observables (HO) at the future $e^{+}{e}^{-}$ Higgs factory (such as CEPC). To optimize constraints of new physics from all available observables, we establish a scheme-independent approach. With this formulation, we treat the SM electroweak parameters and the coefficients of dimension-6 operators on equal footing, which can be fitted simultaneously by the same ${\chi }^2$ function. As deviations from the SM are generally small, we can expand the new physics parameters up to linear order and perform an analytical ${\chi }^2$ fit to derive the potential reach of the new physics scales. We find that the HO from both Higgs produnction and decay rates can probe the new physics scales up to 10TeV (and to 44TeV for the case of gluon-involved operator ${\mathcal{O}}_g$), and the new physics scales of Yukawa-type operators can be probed by the precision Higgs coupling measurements up to (13-25)TeV. Further including the EWPO can push the limit up to 35TeV. From this prospect, we demonstrate that the EWPO measured in the early phase of a Higgs factory can be as important as the Higgs observables. These indirect probes of new physics scales at the Higgs factory can mainly cover the energy range to be directly explored by the next generation hadron colliders of pp(50-100TeV), such as the SPPC and FCC-hh.

   hep-phhep-exJHEP(2016)·70 citations
2. 02*

   Characterising the 750 GeV diphoton excess

   Jérémy Bernon🇫🇷 · Andreas Goudelis🇦🇹 · Sabine Kraml🇫🇷 · Kentarou Mawatari🇫🇷 · Dipan Sengupta🇫🇷

   We study kinematic distributions that may help characterise the recently observed excess in diphoton events at 750 GeV at the LHC Run 2. Several scenarios are considered, including spin-0 and spin-2 750 GeV resonances that decay directly into photon pairs as well as heavier parent resonances that undergo three-body or cascade decays. We find that combinations of the distributions of the diphoton system and the leading photon can distinguish the topology and mass spectra of the different scenarios, while patterns of QCD radiation can help differentiate the production mechanisms. Moreover, missing energy is a powerful discriminator for the heavy parent scenarios if they involve (effectively) invisible particles. While our study concentrates on the current excess at 750 GeV, the analysis is general and can also be useful for characterising other potential diphoton signals in the future.

   hep-phhep-exJHEP(2016)·28 citations
3. 03*

   Light Chiral Dark Sector

   Keisuke Harigaya🇺🇸 · Yasunori Nomura🇺🇸

   An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling of the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimental and cosmological constraints. In a corner of the parameter space, the discrepancy of the muon g-2 between experiments and the standard model prediction can also be ameliorated due to a loop contribution of the dark photon. Smoking-gun signatures of the model include a monophoton signal from the e+ e- collision into a photon and a "dark rho meson." Observation of two processes in e+ e- collision, the mode into the dark photon and that into the dark rho meson, would provide strong evidence for the model.

   hep-phastro-ph.COhep-exPRD(2016)·37 citations
4. 04*

   Top quark mass determination from the energy peaks of b-jets and B-hadrons at NLO QCD

   Kaustubh Agashe🇺🇸 · Doojin Kim🇺🇸 · Roberto Franceschini🇨🇭 · Markus Schulze🇨🇭

   We analyze the energy spectra of $single$ b-jets and B-hadrons resulting from the production and decay of top quarks within the SM at the LHC at the NLO QCD. For both hadrons and jets, we calculate the correlation of the peak of the spectrum with the top quark mass, considering the "energy-peak" as an observable to determine the top quark mass. Such a method is motivated by our previous work where we argued that this approach can have reduced sensitivity to the details of the production mechanism of the top quark, whether it is higher-order QCD effects or new physics contributions. As part of the NLO improvement over the original proposal, we assess the residual sensitivity of the extracted top quark mass to perturbative effects both in top quark production and decay. For a 1% jet energy scale uncertainty (and assuming negligible statistical error), the top quark mass can then be extracted using the energy-peak of b-jets with an error +- (1.2 (exp) + 0.6(th)) GeV. We note that recently the CMS collaboration reported a top quark mass measurement based on the original proposal (with b-jets) so that our result contributes to a precise evaluation of the associated theory uncertainty. In view of the dominant jet energy scale uncertainty in the measurement using b-jets, we also investigate the extraction of the top quark mass from the energy-peak of the corresponding B-hadrons which, in principle, can be measured without this uncertainty. The calculation of the B-hadron energy spectrum is carried out using fragmentation functions at NLO. The dependence on the fragmentation scale turns out to be the largest theoretical uncertainty in this extraction of top quark mass. Future improvement of the treatment of bottom quark hadronization can reduce this uncertainty, rendering methods based on the B-hadron energy-peak competitive for the top quark mass measurement.

   hep-phhep-exEPJC(2016)·37 citations
5. 05*

   Threshold Corrections to Dimension-six Proton Decay Operators in Non-minimal SUSY SU(5) GUTs

   Borut Bajc🇸🇮 · Junji Hisano🇯🇵 · Takumi Kuwahara🇯🇵 · Yuji Omura🇯🇵

   We calculate the high and low scale threshold corrections to the D=6 proton decay mode in supersymmetric SU(5) grand unified theories with higher-dimensional representation Higgs multiplets. In particular, we focus on a missing-partner model in which the grand unified group is spontaneously broken by the 75-dimensional Higgs multiplet and the doublet-triplet splitting problem is solved. We find that in the missing-partner model the D=6 proton decay rate gets suppressed by about 60%, mainly due to the threshold effect at the GUT scale, while the SUSY-scale threshold corrections are found to be less prominent when sfermions are heavy.

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

   Minimal conformal extensions of the Higgs sector

   Alexander J. Helmboldt🇩🇪 · Pascal Humbert🇩🇪 · Manfred Lindner🇩🇪 · Juri Smirnov🇩🇪

   In this work we find the minimal extension of the Standard Model's Higgs sector which can lead to a light Higgs boson via radiative symmetry breaking and is consistent with the phenomenological requirements for a low-energy realization of a conformal theory. The model which turns out to be stable under renormalization group translations is an extension of the Standard Model by two scalar fields, one of which acquires a finite vacuum expectation value and therefore mixes into the physical Higgs. We find that the minimal model predicts a sizable amount of mixing which makes it testable at a collider. In addition to the physical Higgs, the theory's scalar spectrum contains one light and one heavy boson. The heavy scalar's properties render it a potential dark matter candidate.

   hep-phhep-thJHEP(2017)·64 citations
7. 07*

   Pseudoscalar top-Higgs coupling: Exploration of $\mathrm{CP}$-odd observables to resolve the sign ambiguity

   Nicolas Mileo🇦🇷 · Ken Kiers🇺🇸 · Alejandro Szynkman🇦🇷 · Daniel Crane🇺🇸 · Ethan Gegner🇺🇸

   We present a collection of $\mathrm{CP}$-odd observables for the process $pp\to t\left(\to b{\ell }^{+}{\nu }_{\ell }\right)\bar{t}\left(\to \bar{b}{\ell }^{-}{\bar{\nu }}_{\ell }\right)H$ that are linearly dependent on the scalar (${\kappa }_t$) and pseudoscalar (${\tilde{\kappa }}_t$) top-Higgs coupling and hence sensitive to the corresponding relative sign. The proposed observables are based on triple product (TP) correlations that we extract from the expression for the differential cross section in terms of the spin vectors of the top and antitop quarks. In order to explore other possibilities, we progressively modify these TPs, first by combining them, and then by replacing the spin vectors by the lepton momenta or the $t$ and $\bar{t}$ momenta by their visible parts. We generate Monte Carlo data sets for several benchmark scenarios, including the Standard Model (${\kappa }_t=1$, ${\tilde{\kappa }}_t=0$) and two scenarios with mixed $\mathrm{CP}$ properties (${\kappa }_t=1$, ${\tilde{\kappa }}_t=\pm 1$). Assuming an integrated luminosity that is consistent with that envisioned for the High Luminosity Large Hadron Collider, using Monte Carlo-truth and taking into account only statistical uncertainties, we find that the most promising observable can disentangle the "$\mathrm{CP}$-mixed" scenarios with an effective separation of $\sim 19\sigma$. In the case of observables that do not require the reconstruction of the $t$ and $\bar{t}$ momenta, the power of discrimination is up to $\sim 13\sigma$ for the same number of events. We also show that the most promising observables can still disentangle the $\mathrm{CP}$-mixed scenarios when the number of events is reduced to values consistent with expectations for the Large Hadron Collider in the near term.

   hep-phhep-exJHEP(2016)·51 citations
8. 08*

   Pion-nucleon scattering in covariant baryon chiral perturbation theory with explicit Delta resonances

   De-Liang Yao🇩🇪 · D. Siemens🇩🇪 · V. Bernard🇫🇷 · E. Epelbaum🇩🇪 · A. M. Gasparyan🇩🇪 · J. Gegelia🇩🇪 · H. Krebs🇩🇪 · Ulf-G. Meißner🇩🇪

   We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the $S$- and $P$-partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the $D$ and $F$ waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.

   hep-phnucl-thJHEP(2016)·125 citations
9. 09*

   Low energy behaviour of standard model extensions

   Michele Boggia (Albert-Ludwigs-Universitaet, Freiburg)🇩🇪 · Raquel Gomez-Ambrosio (INFN, Turin and Turin U.)🇮🇹 · Giampiero Passarino (INFN, Turin and Turin U.)🇮🇹

   The integration of heavy scalar fields is discussed in a class of BSM models, containing more that one representation for scalars and with mixing. The interplay between integrating out heavy scalars and the Standard Model decoupling limit is examined. In general, the latter cannot be obtained in terms of only one large scale and can only be achieved by imposing further assumptions on the couplings. Systematic low-energy expansions are derived in the more general, non-decoupling scenario, including mixed tree-loop and mixed heavy-light generated operators. The number of local operators is larger than the one usually reported in the literature.

   hep-phJHEP(2016)·58 citations
10. 10*

    Properties of single cluster structure of $d^{\ast }(2380)$ in chiral SU(3) quark model

    Qi-Fang Lü🇨🇳 · Fei Huang🇨🇳 · Yu-Bing Dong🇨🇳 · Peng-Nian Shen🇨🇳 · Zong-Ye Zhang🇨🇳

    The structure of $d^{\ast }(2380)$ is re-studied with the single cluster structure in the chiral SU(3) quark model which has successfully been employed to explain the scattering and binding behaviors of baryonic systems. The mass and width are explicitly calculated with two types of trial wave functions. The result shows that the $(0s{)}^6[6{]}_{orb}$ configuration is easy to convert to the configuration with the same $[6{]}_{orb}$ symmetry but $2\hslash \omega$ excitation back and forth, however, it is seldom to turn into a two-cluster configuration with a (1s) relative motion in between. The resultant mass and width are about $2394$MeV and $25$MeV, respectively, and the stable size is about $0.75fm$, which are consistent with both the results in the two-cluster configuration calculation and the data measured by the COSY collaboration. It seems that the observed $d^{\ast }$ is a six-quark dominated exotic state with a spherical shape and breath mode in the coordinate space. Moreover, if $d^{\ast }$ does have $2\hslash \omega$ excitation, the $d^{\ast }\to np\pi \pi \pi$ decay mode might be a good place to distinguish the real structure of the observed phenomenon by COSY. The masses of various isospin-spin states of six-light-quark systems are also computed. It is shown that by considering the coupling with the configurations with $2\hslash \omega$ excitations, only the mirror state with $IS$=$30$ will be lower down to the place where whose mass is slightly higher than the value of the $\Delta \Delta$ threshold.

    hep-phnucl-thPhys. Rev. D 96, 014036 (2017)·1 citation
11. 11*

    Dark matter decays from non-minimal coupling to gravity

    Oscar Catà🇩🇪 · Alejandro Ibarra🇩🇪 · Sebastian Ingenhütt🇩🇪

    We consider the Standard Model extended with a dark matter particle in curved spacetime, motivated by the fact that the only current evidence for dark matter is through its gravitational interactions, and we investigate the impact on the dark matter stability of terms in the Lagrangian linear in the dark matter field and proportional to the Ricci scalar. We show that this "gravity portal" induces decay even if the dark matter particle only has gravitational interactions, and that the decay branching ratios into Standard Model particles only depend on one free parameter: the dark matter mass. We study in detail the case of a singlet scalar as dark matter candidate, which is assumed to be absolutely stable in flat spacetime due to a discrete $Z_2$ symmetry, but which may decay in curved spacetimes due to a $Z_2$-breaking non-minimal coupling to gravity. We calculate the dark matter decay widths and we set conservative limits on the non-minimal coupling parameter from experiments. The limits are very stringent and suggest that there must exist an additional mechanism protecting the singlet scalar from decaying via this gravity portal.

    hep-phastro-ph.COPRL(2016)·27 citations
12. 12*

    High-Energy Scatterings in Infinite-Derivative Field Theory and Ghost-Free Gravity

    Spyridon Talaganis🇬🇧 · Anupam Mazumdar🇬🇧

    In this paper, we will consider scattering diagrams in the context of infinite-derivative theories. First, we examine a finite-order higher-derivative scalar field theory and find that we cannot eliminate the external momentum divergences of scattering diagrams in the regime of large external momenta. Then, we employ an infinite-derivative scalar toy model and obtain that the external momentum dependence of scattering diagrams is convergent as the external momenta become very large. In order to eliminate the external momentum divergences, one has to dress the bare vertices of the scattering diagrams by considering renormalised propagator and vertex loop corrections to the bare vertices. Finally, we investigate scattering diagrams in the context of a scalar toy model which is inspired by a $ghost-free$ and $singularity-free$ infinite-derivative theory of gravity, where we conclude that infinite derivatives can eliminate the external momentum divergences of scattering diagrams and make the scattering diagrams convergent in the ultraviolet.

    ↳ hep-thgr-qchep-phClass.Quant.Grav.(2016)·49 citations
13. 13*

    Anomalous Maxwell equations for inhomogeneous chiral plasma

    E. V. Gorbar🇺🇦 · I. A. Shovkovy🇺🇸 · S. Vilchinskii🇺🇦 · I. Rudenok🇺🇦 · A. Boyarsky🇳🇱 · O. Ruchayskiy🇩🇰

    Using the chiral kinetic theory we derive the electric and chiral current densities in inhomogeneous relativistic plasma. We also derive equations for the electric and chiral charge chemical potentials that close the Maxwell equations in such a plasma. The analysis is done in the regimes with and without a drift of the plasma as a whole. In addition to the currents present in the homogeneous plasma (Hall current, chiral magnetic, chiral separation, and chiral electric separation effects, as well as Ohm's current) we derive several new terms associated with inhomogeneities of the plasma. Apart from various diffusion-like terms, we find also new dissipation-less terms that are independent of relaxation time. Their origin can be traced to the Berry curvature modifications of the kinetic theory.

    ↳ hep-thcond-mat.mes-hallhep-phPRD(2016)·66 citations
14. 14*

    Conformal Gauge-Yukawa Theories away From Four Dimensions

    Alessandro Codello🇩🇰 · Kasper Langaeble🇩🇰 · Daniel Litim🇬🇧 · Francesco Sannino🇩🇰

    We present the phase diagram and associated fixed points for a wide class of Gauge-Yukawa theories in $d=4+ϵ$ dimensions. The theories we investigate involve non-abelian gauge fields, fermions and scalars in the Veneziano-Witten limit. The analysis is performed in steps, we start with QCD${}_d$ and then we add Yukawa interactions and scalars which we study at next-to- and next-to-next-to-leading order. Interacting infrared fixed points naturally emerge in dimensions lower than four while ultraviolet ones appear above four. We also analyse the stability of the scalar potential for the discovered fixed points. We argue for a very rich phase diagram in three dimensions while in dimensions higher than four certain Gauge-Yukawa theories are ultraviolet complete because of the emergence of an asymptotically safe fixed point.

    ↳ hep-thgr-qchep-lathep-phJHEP(2016)·25 citations
15. 15*

    The Flipped SU(5) String Vacua Classification: A Variation Of The SO(10) Breaking Basis Vector

    Hasan Sonmez🇬🇧

    In this paper, an extension of the classification of flipped SU(5) heterotic-string vacua from [1] with a variation of the SO(10) breaking $\alpha$ basis vector is presented. A statistical sampling in the space of $2^{45}$ flipped SU(5) vacua is explored, where $10^{11}$ distinct GGSO projection configurations are scanned in comparison to the $10^{12}$ GGSO distinct coefficients scanned in the space of $2^{44}$ vacua in [1]. A JAVA code, akin to the one used for the classification in [1], was implemented to explore these. Results presented here indicate that no three generation exophobic vacua exist, which was also found to be the case in [1] as all odd generations were projected out. This paper will also study the details on the comparison between the two classifications achieved and then reflect on future directions in the quest for finding three generation exophobic flipped SU(5) heterotic-string models.

    ↳ hep-thhep-phPRD(2016)·22 citations
16. 16*

    Nonlinear Chiral Transport Phenomena

    Jiunn-Wei Chen🇹🇼 · Takeaki Ishii🇯🇵 · Shi Pu🇩🇪 · Naoki Yamamoto🇯🇵

    We study the nonlinear responses of relativistic chiral matter to the external fields, such as the electric field $\mathbf{E}$, gradients of temperature and chemical potential, $\nabla T$ and $\nabla \mu$. Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter, but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to $\nabla \mu \times \mathbf{E}$ due to the interplay between the effects of the Berry curvature and collisions. We also derive an analogue of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.

    ↳ hep-thcond-mat.mes-hallhep-phPRD(2016)·39 citations
17. 17*

    Wigner transformation, momentum space topology, and anomalous transport

    M.A.Zubkov🇷🇺

    Using derivative expansion applied to the Wigner transform of the two - point Green function we analyse the anomalous quantum Hall effect (AQHE), and the chiral magnetic effect (CME). The corresponding currents are proportional to the momentum space topological invariants. We reproduce the conventional expression for the Hall conductivity in $2+1$ D. In $3+1$ D our analysis allows to explain systematically the AQHE in topological insulators and Weyl semimetals. At the same time using this method it may be proved, that the equilibrium CME is absent in the wide class of solids, as well as in the properly regularized relativistic quantum field theory.

    ↳ cond-mat.mes-hallhep-phAnnals Phys.(2016)·49 citations
18. 18*

    Simultaneous chiral symmetry restoration and deconfinement - Consequences for the QCD phase diagram

    Thomas Klahn🇵🇱 · Tobias Fischer🇵🇱 · Matthias Hempel🇨🇭

    For studies of quark matter in astrophysical scenarios the thermodynamic bag model (tdBag) is commonly employed. Although successful, it does not account for dynamical chiral symmetry breaking (D$\chi$SB) and repulsions due to the vector interaction which is crucial to explain recent observations of massive, two solar mass neutron stars. In Klähn & Fischer (2015) we developed the novel vBag quark matter model which takes these effects into account. This article extends vBag to finite temperatures and isospin asymmetry. Another particular feature of vBag is the determination of the deconfinement bag constant $B_{\mathrm{dc}}$ from a given hadronic equation of state (EoS) in order to ensure that chiral and deconfinement transitions coincide. We discuss consequences of this novel approach for the phase transition construction, the phase diagram, and implications for protoneutron stars.

    ↳ nucl-thastro-ph.HEhep-phApJ(2017)·34 citations
19. 19*

    Path integral for multi-field inflation

    Jinn-Ouk Gong🇰🇷 · Min-Seok Seo🇰🇷 · Gary Shiu🇺🇸

    We develop the path integral formalism for studying cosmological perturbations in multi-field inflation, which is particularly well suited to study quantum theories with gauge symmetries such as diffeomorphism invariance. We formulate the gauge fixing conditions based on the Poisson brackets of the constraints, from which we derive two convenient gauges that are appropriate for multi-field inflation. We then adopt the in-in formalism to derive the most general expression for the power spectrum of the curvature perturbation including the corrections from the interactions of the curvature mode with other light degrees of freedom. We also discuss the contributions of the interactions to the bispectrum.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2016)·20 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.