Fri·Jan 20, 2017Friday·January 20, 2017

1. 01*

   Investigating the influence of diffractive interactions on ultra - high energy extensive air showers

   L.B. Arbeletche🇧🇷 · V.P. Goncalves🇧🇷 · M.A. Muller🇧🇷

   The understanding of the basic properties of the ultra - high energy extensive air showers is strongly dependent on the description of the hadronic interactions in a energy range beyond that probed by the LHC. One of the uncertainties present in the modeling of the air showers is the treatment of diffractive interactions, which are dominated by non - perturbative physics and usually described by phenomenological models. These interactions are expect to affect the development of the air showers, since they provide a way of transporting substantial amounts of energy deep in the atmosphere, modifying the global characteristics of the shower profile. In this paper we investigate the impact of the diffractive interactions in the observables that can be measured in hadronic collisions at high energies and ultra - high energy cosmic ray interactions. We consider three distinct phenomenological models for the treatment of diffractive physics and estimate the influence of these interactions on the elasticity, number of secondaries, longitudinal air shower profiles and muon densities for proton - air and iron - air collisions at different primary energies. Our results demonstrate that the diffractive events has a non - negligible effect on the observables and that the distinct approaches for these interactions, present in the phenomenological models, are an important source of theoretical uncertainty for the description of the extensive air showers.

   hep-phastro-ph.HEhep-exInt.J.Mod.Phys.A(2018)·5 citations
2. 02*

   Two-parton scattering in the high-energy limit

   Simon Caron-Huot🇨🇦 · Einan Gardi🇬🇧 · Leonardo Vernazza🇬🇧

   Considering $2\to 2$ gauge-theory scattering with general colour in the high-energy limit, we compute the Regge-cut contribution to three loops through next-to-next-to-leading high-energy logarithms (NNLL) in the signature-odd sector. Our formalism is based on using the non-linear Balitsky-JIMWLK rapidity evolution equation to derive an effective Hamiltonian acting on states with a fixed number of Reggeized gluons. A new effect occurring first at NNLL is mixing between states with $k$ and $k+2$ Reggeized gluons due non-diagonal terms in this Hamiltonian. Our results are consistent with a recent determination of the infrared structure of scattering amplitudes at three loops, as well as a computation of $2\to 2$ gluon scattering in $\mathcal{N}=4$ super Yang-Mills theory. Combining the latter with our Regge-cut calculation we extract the three-loop Regge trajectory in this theory. Our results open the way to predict high-energy logarithms through NNLL at higher-loop orders.

   hep-phhep-thJHEP(2017)·85 citations
3. 03*

   Models of Supersymmetry for Dark Matter

   Carlos Munoz🇪🇸

   A brief review of supersymmetric models and their candidates for dark matter is carried out. The neutralino is a WIMP candidate in the MSSM where $R$-parity is conserved, but this model has the $\mu$ problem. There are natural solutions to this problem that necessarily introduce new structure beyond the MSSM, including new candidates for dark matter. In particular, in an extension of the NMSSM, the right-handed sneutrino can be used for this job. In $R$-parity violating models such as the $\mu \nu$SSM, the gravitino can be the dark matter, and could be detected by its decay products in gamma-ray experiments.

   hep-phastro-ph.COastro-ph.HEhep-thEPJ Web Conf.(2017)·22 citations
4. 04*

   A Comprehensive Framework for Studying $W^{\prime }$ and $Z^{\prime }$ Bosons at Hadron Colliders with Automated Jet Veto Resummation

   Benjamin Fuks🇫🇷 · Richard Ruiz🇬🇧

   The production of high-mass, color-singlet particles in hadron colliders is universally accompanied by initial state QCD radiation that is predominantly soft with respect to the hard process scale $Q$ and/or collinear with respect to the beam axis. At TeV-scale colliders, this is in contrast to top quark and multijet processes, which, by definition, are hard and central. Consequently, vetoing events with jets possessing transverse momenta above $p_T^{\mathrm{Veto}}$ in searches for new color-singlet states can efficiently reduce non-singlet backgrounds, thereby increasing experimental sensitivity. To quantify this generic observation, we investigate the production and leptonic decay of a Sequential Standard Model $W^{\prime }$ boson at the 13 TeV LHC. We systematically consider signal and background processes at next-to-leading-order (NLO) in QCD with parton shower (PS) matching; for color-singlet channels, we resum Sudakov logarithms of the form ${\alpha }_s^j(p_T^{\mathrm{Veto}}){\log }^k(Q/p_T^{\mathrm{Veto}})$ up to next-to-next-to-leading logarithmic accuracy (NNLL) with NLO matching. We obtain our results using the MadGraph5aMC@NLO and MadGraph5aMC@NLO-SCET frameworks, respectively. Associated FeynRules model files capable of handling NLO+PS- and NLO+NNLL-accurate computations are publicly available. We find that within their given uncertainties, both the NLO+PS and NLO+NNLL(veto) calculations give accurate and consistent predictions. Consequently, jet vetoes applied to color-singlet processes can be reliably modeled at the NLO+PS level. With respect to a $b$-jet veto of $p_T^{\mathrm{Veto}}=30$ GeV, flavor-agnostic vetoes of $p_T^{\mathrm{Veto}}=30-40$ GeV can further reduce single top and $t\overline{t}$ rates by a factor of 2-50 at a mild cost of the signal rate. Jet vetoes can increase signal-to-noise ratios by roughly 10\% for light $W^{\prime }$ boson masses of 30-50 GeV and 25\%-250\% for masses of 300-800 GeV.

   hep-phhep-exJHEP(2017)·47 citations
5. 05*

   Automated calculation of matrix elements and physics motivated observables

   Z. Was🇵🇱

   The central aspect of my personal scientific activity, has focused on calculations useful for interpretation of High Energy accelerator experimental results, especially in a domain of precision tests of the Standard Model. My activities started in early 80's, when computer support for algebraic manipulations was in its infancy. But already then it was important for my work. It brought a multitude of benefits, but at the price of some inconvenience for physics intuition. Calculations became more complex, work had to be distributed over teams of researchers and due to automatization, some aspects of the intermediate results became more difficult to identify. In my talk I will not be very exhaustive, I will present examples from my personal research only: (i) calculations of spin effects for the process e+ e- to tau+tau- gamma at Petra/PEP energies, calculations (with the help of the {\tt Grace} system of Minami-tateya group) and phenomenology of spin amplitudes for (ii) e+ e- to 4f and for (iii) e+ e- to nu_e bar nu_e gamma gamma processes, (iv) phenomenology of CP-sensitive observables for Higgs boson parity in H to tau+ tau- , tau+- to nu 2(3)pi cascade decays

   hep-phJ.Phys.Conf.Ser.(2017)·0 citations
6. 06*

   Full parameter scan of the Zee model: exploring Higgs lepton flavor violation

   Juan Herrero-García🇦🇺 · Tommy Ohlsson🇸🇪 · Stella Riad🇸🇪 · Jens Wirén🇸🇪

   We study the general Zee model, which includes an extra Higgs scalar doublet and a new singly-charged scalar singlet. Neutrino masses are generated at one-loop level, and in order to describe leptonic mixing, both the Standard Model and the extra Higgs scalar doublets need to couple to leptons (in a type-III two-Higgs doublet model), which necessarily generates large lepton flavor violating signals, also in Higgs decays. Imposing all relevant phenomenological constraints and performing a full numerical scan of the parameter space, we find that both normal and inverted neutrino mass orderings can be fitted, although the latter is disfavored with respect to the former. In fact, inverted ordering can only be accommodated if ${\theta }_{23}$ turns out to be in the first octant. A branching ratio for $h\to \tau \mu$ of up to $10^{-2}$ is allowed, but it could be as low as $10^{-6}$. In addition, if future expected sensitivities of $\tau \to \mu \gamma$ are achieved, normal ordering can be almost completely tested. Also, $\mu e$ conversion is expected to probe large parts of the parameter space, excluding completely inverted ordering if no signal is observed. Furthermore, non-standard neutrino interactions are found to be smaller than $10^{-6}$, which is well below future experimental sensitivity. Finally, the results of our scan indicate that the masses of the additional scalars have to be below $2.5$ TeV, and typically they are lower than that and therefore within the reach of the LHC and future colliders.

   hep-phJHEP(2017)·73 citations
7. 07*

   ALPs Effective Field Theory and Collider Signatures

   I. Brivio🇩🇰 · M.B. Gavela🇪🇸 · L. Merlo🇪🇸 · K. Mimasu🇬🇧 · J.M. No🇬🇧 · R. del Rey🇪🇸 · V.Sanz🇬🇧

   We study the leading effective interactions between the Standard Model fields and a generic singlet CP-odd (pseudo)Goldstone boson. Two possible frameworks for electroweak symmetry breaking are considered: linear and non-linear. For the latter case, the basis of leading effective operators is determined and compared with that for the linear expansion. Associated phenomenological signals at colliders are explored for both scenarios, deriving new bounds and analyzing future prospects, including LHC and High Luminosity LHC sensitivities. Mono-$Z$, mono-$W$, $W$-photon plus missing energy and on-shell top final states are most promising signals expected in both frameworks. In addition, non-standard Higgs decays and mono-Higgs signatures are especially prominent and expected to be dominant in non-linear realizations.

   hep-phEPJC(2017)·343 citations
8. 08*

   Probing sub-GeV dark sectors via high energy proton beams at LBNF/DUNE and MiniBooNE

   Claudia Frugiuele🇮🇱

   We study the sensitivity to sub-GeV dark sectors of high energy ($\ge 100$ GeV) proton fixed target experiments such as the Main Injector and the future Long-Baseline Neutrino Facility (LBNF). We focus on off-axis detectors since they have been shown to be the ideal location to reduce the neutrino background. We consider MiniBooNE as an off-axis detector for the NuMI facility and a hypotetical detector for LBNF located 200 m away from the target and 6.5 degrees off-axis. We find that with the existing data, MiniBoone can explore new regions of the parameter space for leptophobic dark forces in the 100 MeV- few GeV mass range. The dedicated MiniBooNE run in beam dump mode would further improve the reach for even lighter masses. Therefore, MiniBooNE has the potential to be one of the most sensitive probe of leptophobic dark forces for masses between 1 MeV-10 GeV.

   hep-phPRD(2017)·26 citations
9. 09*

   Hybrid Anomaly and Gravity Mediation for Electroweak Supersymmetry

   Bin Zhu🇨🇳 · Ran Ding🇨🇳 · Tianjun Li🇨🇳

   We propose a hybrid mediation and hybrid supersymmetry breaking. In particular the RG-invariant anomaly mediation is considered. Together with additional gravity mediation the slepton tachyon problem of anomaly mediation is solved automatically. The special properties are that all of color sparticles masses fall into several TeV region due to the large $m_0$ and $m_{32}$ which are well beyond the scope of current LHC Run II limits. Unlike the gauge mediation, the dark matter candidate is still the lightest neutralino and the correct dark matter relic density can be realized within the framework of mixed axion-wino dark matter. Due to the existence of multi-component of axion-wino dark matter, the direct detection cross section is suppressed to evade the tightest LUX, PandaX bound. Furthermore the fine-tuning is under control when the single scale supersymmetry breaking mechanism is adapted.

   hep-phInt.J.Mod.Phys.A(2018)·1 citation
10. 10*

    Forward two-photon exchange in elastic lepton-proton scattering and hyperfine-splitting correction

    Oleksandr Tomalak🇩🇪

    We relate the forward two-photon exchange (TPE) amplitudes to integrals of the inclusive lepton-proton scattering cross sections. These relations yield an alternative way for the evaluation of the TPE correction to hyperfine-splitting (HFS) in the hydrogen-like atoms with an equivalent to the standard approach (Iddings, Drell and Sullivan) result implying the Burkhardt-Cottingham sum rule. For evaluation of the individual effects (e.g., elastic contribution) our approach yields a distinct result. We compare both methods numerically on examples of the elastic contribution and the full TPE correction to HFS in electronic and muonic hydrogen.

    hep-phnucl-exnucl-thphysics.atom-phEPJC(2017)·31 citations
11. 11*

    PEN: a low energy test of lepton universality

    D. Pocanic🇺🇸 · L.P. Alonzi🇺🇸 · V.A. Baranov🇷🇺 · W. Bertl🇨🇭 · M. Bychkov🇺🇸 · Yu.M. Bystritsky🇷🇺 · E. Frlez🇺🇸 · C.J. Glaser🇺🇸 · V.A. Kalinnikov🇷🇺 · N.V. Khomutov🇷🇺 · A.S. Korenchenko🇷🇺 · S.M. Korenchenko🇷🇺 and 15 other authors

    Allowed charged $\pi$ meson decays are characterized by simple dynamics, few available decay channels, mainly into leptons, and extremely well controlled radiative and loop corrections. In that sense, pion decays represent a veritable triumph of the standard model (SM) of elementary particles and interactions. This relative theoretical simplicity makes charged pion decays a sensitive means for testing the underlying symmetries and the universality of weak fermion couplings, as well as for studying pion structure and chiral dynamics. Even after considerable recent improvements, experimental precision is lagging far behind that of the theoretical description for pion decays. We review the current state of experimental study of the pion electronic decay ${\pi }^{+}\to e^{+}{\nu }_e(\gamma )$, or ${\pi }_{e2(\gamma )}$, where the $(\gamma )$ indicates inclusion and explicit treatment of radiative decay events. We briefly review the limits on non-SM processes arising from the present level of experimental precision in ${\pi }_{e2(\gamma )}$ decays. Focusing on the PEN experiment at the Paul Scherrer Institute (PSI), Switzerland, we examine the prospects for further improvement in the near term.

    ↳ hep-exhep-phnucl-exPoS(2017)·2 citations
12. 12*

    Monopole and Polyakov loop

    Aiichi Iwazaki🇯🇵

    We propose a new order parameter of a $Z_N$ symmetry in SU(N) gauge theories in $4$ dimensional Minkowski space-time, assuming spatial periodic boundary conditions. It is given by $Tr(P\exp (i{\int }_c{A}_{\mu }d{x}^{\mu }))$ where the spatial path $c$ is taken, for example, along $x_1$ axis. The parameter vanishes when the $Z_N$ symmetry is preserved. We calculate the contribution of QCD monopoles to the order parameter and show that when the monopoles condense $⟨\Phi ⟩\ne 0$, it vanishes, while it does not vanish when they do not condense. These calculations are performed using a monopole field $\Phi$ canonically quantized in a model of dual superconductor.

    ↳ hep-thhep-phPRD(2017)·1 citation
13. 13*

    Inflation and Conformal Invariance: The Perspective from Radial Quantization

    Alex Kehagias🇬🇷 · Antonio Riotto🇨🇭

    According to the dS/CFT correspondence, correlators of fields generated during a primordial de Sitter phase are constrained by three-dimensional conformal invariance. Using the properties of radially quantized conformal field theories and the operator-state correspondence, we glean information on some points. The Higuchi bound on the masses of spin-s states in de Sitter is a direct consequence of reflection positivity in radially quantized CFT${}_3$ and the fact that scaling dimensions of operators are energies of states. The partial massless states appearing in de Sitter correspond from the boundary CFT${}_3$ perspective to boundary states with highest weight for the conformal group. We discuss inflationary consistency relations and the role of asymptotic symmetries which transform asymptotic vacua to new physically inequivalent vacua by generating long perturbation modes. We show that on the CFT${}_3$ side, asymptotic symmetries have a nice quantum mechanics interpretation. For instance, acting with the asymptotic dilation symmetry corresponds to evolving states forward (or backward) in "time" and the charge generating the asymptotic symmetry transformation is the Hamiltonian itself. Finally, we investigate the symmetries of anisotropic inflation and show that correlators of four-dimensional free scalar fields can be reproduced in the dual picture by considering an isotropic three-dimensional boundary enjoying dilation symmetry, but with a nonvanishing vacuum expectation value of the boundary stress-energy momentum tensor.

    ↳ hep-thastro-ph.COgr-qchep-phFortsch.Phys.(2017)·15 citations
14. 14*

    Quasinormal modes of charged magnetic black branes & chiral magnetic transport

    Martin Ammon🇩🇪 · Matthias Kaminski🇺🇸 · Roshan Koirala🇺🇸 · Julian Leiber🇩🇪 · Jackson Wu🇺🇸

    We compute quasinormal modes (QNMs) of the metric and gauge field perturbations about black branes electrically and magnetically charged in the Einstein-Maxwell-Chern-Simons theory. By the gauge/gravity correspondence, this theory is dual to a particular class of field theories with a chiral anomaly, in a thermal charged plasma state subjected to a constant external magnetic field, $B$. The QNMs are dual to the poles of the two-point functions of the energy-momentum and axial current operators, and they encode information about the dissipation and transport of charges in the plasma. Complementary to the gravity calculation, we work out the hydrodynamic description of the dual field theory in the presence of a chiral anomaly, and a constant external $B$. We find good agreement with the weak field hydrodynamics, which can extend beyond the weak $B$ regime into intermediate regimes. Furthermore, we provide results that can be tested against thermodynamics and hydrodynamics in the strong $B$ regime. We find QNMs exhibiting Landau level behavior, which become long-lived at large $B$ if the anomaly coefficient exceeds a critical magnitude. Chiral transport is analyzed beyond the hydrodynamic approximation for the five (formerly) hydrodynamic modes, including a chiral magnetic wave.

    ↳ hep-thhep-phnucl-thJHEP(2017)·54 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.