Thu·Aug 25, 2016Thursday·August 25, 2016

1. 01*

   Matter neutrino oscillations, an approximation in a parametrization-free framework

   L. J. Flores🇲🇽 · O. G. Miranda🇲🇽

   Neutrino oscillations are one of the most studied and successful phenomena since the establishment of the solar neutrino problem in late 1960's. In this work we discuss the exact expressions for the probability P_{\alpha\beta} in a constant density medium, in terms of the standard vacuum parameters and the medium density. Besides of being compact, these expressions are independent of any particular parametrization, which could be helpful in the application of unitary tests of the mixing matrix. In addition, we introduce a new approximation on P_{\alpha\beta} and compare it with the most commonly used, discussing their main differences.

   hep-phJ.Phys.Conf.Ser.(2016)·1 citation
2. 02*

   Nambu-Goldstone Boson Hypothesis for Squarks and Sleptons in Pure Gravity Mediation

   Tsutomu T. Yanagida🇯🇵 · Wen Yin🇯🇵 · Norimi Yokozaki🇯🇵

   We point out that a hypothesis of squarks and sleptons being Nambu-Goldstone (NG) bosons is consistent with pure gravity mediation or minimal split supersymmetry (SUSY). As a concrete example, we consider a SUSY $E_7/SU(5)\times U(1{)}^3$ non-linear sigma model in the framework of pure gravity mediation. The model accommodates three families of the quark and lepton chiral multiplets as (pseudo) NG multiplets of the Kahler manifold, which may enable us to understand the origin and number of the families. We point out that squarks in the first and second generations are likely to be as light as a few TeV if the observed baryon asymmetry is explained by the thermal leptogenesis; therefore, these colored particles can be discovered at the LHC Run-2 or at the high luminosity LHC.

   hep-phhep-exJHEP(2016)·23 citations
3. 03*

   Probing the Electroweak Phase Transition with Higgs Factories and Gravitational Waves

   Peisi Huang🇺🇸 · Andrew J. Long🇺🇸 · Lian-Tao Wang🇺🇸

   After the discovery of the Higgs boson, understanding the nature of electroweak symmetry breaking and the associated electroweak phase transition has become the most pressing question in particle physics. Answering this question is a priority for experimental studies. Data from the LHC and future lepton collider-based Higgs factories may uncover new physics coupled to the Higgs boson, which can induce the electroweak phase transition to become first order. Such a phase transition generates a stochastic background of gravitational waves, which could potentially be detected by a space-based gravitational wave interferometer. In this paper, we survey a few classes of models in which the electroweak phase transition is strongly first order. We identify the observables that would provide evidence of these models at the LHC and next-generation lepton colliders, and we assess whether the corresponding gravitational wave signal could be detected by eLISA. We find that most of the models with first order electroweak phase transition can be covered by the precise measurements of Higgs couplings at the proposed Higgs factories. We also map out the model space that can be probed with gravitational wave detection by eLISA.

   hep-phastro-ph.COPRD(2016)·177 citations
4. 04*

   Kinetic Mixing at Strong Coupling

   Michele Del Zotto🇺🇸 · Jonathan J. Heckman🇺🇸 · Piyush Kumar🇺🇸 · Arada Malekian🇺🇸 · Brian Wecht🇺🇸

   A common feature of many string-motivated particle physics models is additional strongly coupled U(1)'s. In such sectors, electric and magnetic states have comparable mass, and integrating out modes also charged under U(1) hypercharge generically yields CP preserving electric kinetic mixing and CP violating magnetic kinetic mixing terms. Even though these extra sectors are strongly coupled, we show that in the limit where the extra sector has approximate N = 2 supersymmetry, we can use formal methods from Seiberg-Witten theory to compute these couplings. We also calculate various quantities of phenomenological interest such as the cross section for scattering between visible sector states and heavy extra sector states, as well as the effects of supersymmetry breaking induced from coupling to the MSSM.

   hep-phhep-thPRD(2017)·21 citations
5. 05*

   Studying the physics potential of long-baseline experiments in terms of new sensitivity parameters

   Mandip Singh🇮🇳

   We investigate physics opportunities to constraint leptonic CP-violation phase ${\delta }_{CP}$ through numerical analysis of working neutrino oscillation probability parameters, in the context of long base line experiments. Numerical analysis of two parameters, the " transition probability ${\delta }_{CP}$ phase sensitivity parameter ($A^M$) " and " CP-violation probability ${\delta }_{CP}$ phase sensitivity parameter ($A^{CP}$) ", as function of beam energy and/or base line has been preferably carried out. It is an elegant technique to broadly analyze different experiments to constraint ${\delta }_{CP}$ phase and also to investigate mass hierarchy in the leptonic sector. The positive and negative values of parameter $A^{CP}$ corresponding to either of hierarchy in the specific beam energy ranges, could be a very promising way to explore mass hierarchy and ${\delta }_{CP}$ phase. The keys to more robust bounds on ${\delta }_{CP}$ phase are improvements of the involved detection techniques to explore bit low energy and relatively long base line regions with better experimental accuracy.

   hep-phPTEP(2016)·0 citations
6. 06*

   Gauge-Independent Scales Related to the Standard Model Vacuum Instability

   Jose R. Espinosa🇪🇸 · Mathias Garny🇨🇭 · Thomas Konstandin🇩🇪 · Antonio Riotto🇨🇭

   The measured (central) values of the Higgs and top quark masses indicate that the Standard Model (SM) effective potential develops an instability at high field values. The scale of this instability, determined as the Higgs field value at which the potential drops below the electroweak minimum, is about $10^{11}$ GeV. However, such a scale is unphysical as it is not gauge-invariant and suffers from a gauge-fixing uncertainty of up to two orders of magnitude. Subjecting our system, the SM, to several probes of the instability (adding higher order operators to the potential; letting the vacuum decay through critical bubbles; heating up the system to very high temperature; inflating it) and asking in each case physical questions, we are able to provide several gauge-invariant scales related with the Higgs potential instability.

   hep-phastro-ph.COhep-thPRD(2017)·68 citations
7. 07*

   Low-energy relation for the trace of the energy-momentum tensor in QCD and the gluon condensate in a magnetic field

   N.O. Agasian🇷🇺

   A treatment is given of the nonperturbative QCD vacuum in a magnetic field. The low-energy equation for the trace of the energy-momentum tensor in a magnetic field is derived. It is shown that the derivatives with respect to a magnetic field of the quark and gluon contributions to the trace of the energy-momentum tensor are equal. The dependence of the gluon condensate on the magnetic field strength is derived both for strong and weak fields.

   hep-phhep-latJETP Lett.(2016)·4 citations
8. 08*

   Hadron Diffraction: Results and Problems

   V. A. Petrov🇷🇺

   This is a cursory review of diffractive studies ( mostly elastic scattering)at the LHC with physical interpretation of the experimental data and comments to related problems of theory.

   hep-phEPJ Web Conf.(2016)·2 citations
9. 09*

   Depolarization of high-energy neutral particles in crystals and the possibility to measure anomalous magnetic moments of short-lived hyperons

   V.G. Baryshevsky🇧🇾

   The degree of depolarization of neutral particles in crystals can reach tens of percents over the crystal length of several centimeters, which can be the basis for possible experimental application of the depolarization effect for measuring anomalous magnetic moments of short-lived neutral hyperons.

   hep-ph3 citations
10. 10*

    Effects of $\rho$-meson width on pion distributions in heavy-ion collisions

    Pasi Huovinen🇵🇱 · Pok Man Lo🇵🇱 · Michał Marczenko🇵🇱 · Kenji Morita🇯🇵 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱

    The influence of the finite width of $\rho$ meson on the pion momentum distribution is studied quantitatively in the framework of the S-matrix approach combined with a blast-wave model to describe particle emissions from an expanding fireball. We find that the proper treatment of resonances which accounts for their production dynamics encoded in data for partial wave scattering amplitudes can substantially modify spectra of daughter particles originating in their two body decays. In particular, it results in an enhancement of the low-$p_T$ pions from the decays of $\rho$ mesons which improves the quantitative description of the pion spectra in heavy ion collisions obtained by the ALICE collaboration at the LHC energy.

    hep-phnucl-thPLB(2017)·40 citations
11. 11*

    Revised variational approach to QCD in Coulomb gauge

    Davide R. Campagnari🇩🇪 · Ehsan Ebadati🇩🇪 · Hugo Reinhardt🇩🇪 · Peter Vastag🇩🇪

    The variational approach to QCD in Coulomb gauge is revisited. By assuming the non-Abelian Coulomb potential to be given by the sum of its infrared and ultraviolet parts, i.e.~by a linearly rising potential and an ordinary Coulomb potential, and by using a Slater determinant ansatz for the quark wave functional, which contains the coupling of the quarks and the gluons with two different Dirac structures, we obtain variational equations for the kernels of the fermionic vacuum wave functional, which are free of ultraviolet divergences. Thereby, a Gaussian type wave functional is assumed for the gluonic part of the vacuum. By using the results of the pure Yang--Mills sector for the gluon propagator as input, we solve the equations for the fermionic kernels numerically and calculate the quark condensate and the effective quark mass in leading order. Assuming a value of ${\sigma }_{\mathrm{C}}=2.5\sigma$ for the Coulomb string tension (where $\sigma$ is the usual Wilsonian string tension) the phenomenological value of the quark condensate $⟨\bar{\psi }\psi ⟩\simeq (-235\mathrm{MeV}{)}^3$ is reproduced with a value of $g\simeq 2.1$ for the strong coupling constant of the quark-gluon vertex.

    hep-phhep-thPRD(2016)·27 citations
12. 12*

    On Friedrichs Model with Two Continuum States

    Zhiguang Xiao🇨🇳 · Zhi-Yong Zhou🇨🇳

    The Friedrichs model with one discrete state coupled to more than one continuum is studied. The exact eigenstates for the full Hamiltonian can be solved explicitly. The discrete state is found to generate more than one virtual state pole or more than one pair of resonance poles in different Riemann sheets in different situations. The form factors could also generate new states on different sheets. All these states can appear in the generalized completeness relation.

    hep-phnucl-thquant-phJ.Math.Phys.(2017)·27 citations
13. 13*

    On properties of the exotic hadrons from QCD sum rules

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇷🇺

    We discuss the specific features of extracting properties of the exotic polyquark hadrons (tetraquarks, pentaquarks) compared to the usual hadrons by the QCD sum-rule approach. In the case of the ordinary hadrons, already the one-loop leading-order correlation functions provide the bulk of the hadron observables, e.g., of the form factor; inclusion of radiative corrections modifies already nonzero one-loop contributions. In the case of an exotic hadron, the situation is qualitatively different: discussing strong decays of an exotic tetraquark meson, which provide the main contribution to its width, we show that the disconnected leading-order diagrams are not related to the tetraquark properties. For a proper description of the tetraquark decay width, it is mandatory to calculate specific radiative corrections which generate the connected diagrams.

    hep-phEPJ Web Conf.(2016)·1 citation
14. 14*

    Charge radii of heavy flavored mesons in a potential model

    T Das · D K Choudhury · K K Pathak · N S Bordoloi

    We report the results for charge radii of heavy flavored mesons ($D^{+},D^0,D_s^{+},B^{+},B^0,B_s^0$) in an improved QCD potential model. To enhance the effectiveness of short range and long range effect of the potential $V(r)=-4\frac{{\alpha }_s}{3r}+br+c$ in the perturbative procedure a cut-off parameter $r^P$ is introduced as an integration limit. The obtained results are found to be comparable with other available data. The limitation of the approach is discussed in the manuscript.

    hep-ph10 citations
15. 15*

    Modelling electroweak physics for the forward region

    Marek Sirendi🇬🇧

    This note presents a study of matching and merging schemes and weak showering at the LHC as applied to the production of electroweak bosons in association with jets. These advanced theoretical tools are seen to provide a good description of event shapes in the central region when compared to measurements performed by the ATLAS and CMS collaborations at a centre-of-mass energy of 7 TeV. Matching and merging schemes also provide a superior description of forward $Z+$jets production. The study constitutes a test of matching and merging schemes in a novel region of phase space and can be considered as a validation of the universality of these techniques. Finally, it was determined that current measurements of electroweak physics at LHCb do not yet fully probe the effect of weak showers.

    hep-ph1 citation
16. 16*

    RG Flows and Bifurcations

    Sergei Gukov🇩🇪

    Interpreting RG flows as dynamical systems in the space of couplings we produce a variety of constraints, global (topological) as well as local. These constraints, in turn, rule out some of the proposed RG flows and also predict new phases and fixed points, surprisingly, even in familiar theories such as O(N) model, QED-3, or QCD-4.

    ↳ hep-thcond-mat.str-elhep-phmath.DSNPB(2017)·111 citations
17. 17*

    Study of W and Z Boson Production in Proton-Lead Collisions at the LHC with KP Nuclear Parton Distributions

    Peng Ru🇨🇳 · S. A. Kulagin🇷🇺 · R. Petti🇺🇸 · Ben-Wei Zhang🇨🇳

    We present a detailed study of the (pseudo)rapidity distributions of massive vector bosons produced in p+p and p+Pb collisions at the LHC within the next-to-leading order approximation in perturbative quantum chromodynamics. In particular, we discuss the impact of different cold nuclear matter effects on this process using the nuclear parton distributions calculated from the microscopic model developed by Kulagin and Petti (KP). This model was successfully applied to study nuclear effects in the deep-inelastic scattering and the Drell-Yan reactions off various (fixed) target nuclei. Results are compared with the recent CMS and ATLAS p+Pb data with \sqrt{s}=5.02 TeV per two colliding nucleons. We found an excellent agreement between the predictions of the KP model and the recent LHC data on W+- and Z0 production in p+Pb collisions, including the differential cross sections, the forward-backward asymmetries, and W charge asymmetry. We also discuss the sensitivity of the current and future LHC data to the underlying mechanisms responsible for the nuclear modifications of parton density functions.

    ↳ nucl-thhep-exhep-phPRD(2016)·36 citations
18. 18*

    On the strength of the $U_A(1)$ anomaly at the chiral phase transition in $N_f=2$ QCD

    Bastian B. Brandt🇩🇪 · Anthony Francis🇨🇦 · Harvey B. Meyer🇩🇪 · Owe Philipsen🇩🇪 · Daniel Robaina🇩🇪 · Hartmut Wittig🇩🇪

    We study the thermal transition of QCD with two degenerate light flavours by lattice simulations using $O(a)$-improved Wilson quarks. Temperature scans are performed at a fixed value of $N_t=(aT{)}^{-1}=16$, where $a$ is the lattice spacing and $T$ the temperature, at three fixed zero-temperature pion masses between 200 MeV and 540 MeV. In this range we find that the transition is consistent with a broad crossover. As a probe of the restoration of chiral symmetry, we study the static screening spectrum. We observe a degeneracy between the transverse isovector vector and axial-vector channels starting from the transition temperature. Particularly striking is the strong reduction of the splitting between isovector scalar and pseudoscalar screening masses around the chiral phase transition by at least a factor of three compared to its value at zero temperature. In fact, the splitting is consistent with zero within our uncertainties. This disfavours a chiral phase transition in the $O(4)$ universality class.

    ↳ hep-lathep-phnucl-thJHEP(2016)·114 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.