Mon·Nov 16, 2015Monday·November 16, 2015

1. 01*

   New Physics in $B$ decays

   Andreas Crivellin🇨🇭

   While the LHC did not observe direct evidence for physics beyond the standard model, indirect hints for new physics were uncovered in the flavour sector in the decays $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$, $B\to K{\mu }^{+}{\mu }^{-}/B\to K{e}^{+}{e}^{-}$, $B_s\to \varphi {\mu }^{+}{\mu }^{-}$, $B\to D^{(\ast )}\tau \nu$ and $h\to {\tau }^{\pm }{\mu }^{\mp }$. Each observable deviates from the SM predictions at the $2-3\sigma$ level only, but combining all $b\to s{\mu }^{+}{\mu }^{-}$ data via a global fit, one finds $4-5\sigma$ difference for NP compared to the SM and combining $B\to D^{\ast }\tau \nu$ with $B\to D\tau \nu$ one obtains $3.9\sigma$. While $B\to D^{(\ast )}\tau \nu$ and $h\to \tau \mu$ can be naturally explained by an extended Higgs sector, the $b\to s{\mu }^{+}{\mu }^{-}$ anomalies point at a $Z^{\prime }$ gauge boson. However, it is also possible to explain $B\to D^{(\ast )}\tau \nu$ and $b\to s{\mu }^{+}{\mu }^{-}$ simultaneously with leptoquarks while their effect in $h\to {\tau }^{\pm }{\mu }^{\mp }$ is far too small to account for current data. Combining a 2HDM with a gauged $L_{\mu }-L_{\tau }$ symmetry allows for explaining the $b\to s{\mu }^{+}{\mu }^{-}$ anomalies in combination with $h\to {\tau }^{\pm }{\mu }^{\mp }$, predicting interesting correlations with $\tau \to 3\mu$. In the light of these deviations from the SM we also discuss the possibilities of observing lepton flavour violating $B$ decays (e.g. $B\to K^{(\ast )}{\tau }^{\pm }{\mu }^{\mp }$ and $B_s\to {\tau }^{\pm }{\mu }^{\mp }$).

   hep-phhep-exEPJ Web Conf.(2016)·0 citations
2. 02*

   Progress in Electroweak Symmetry Breaking

   S. Dawson🇺🇸

   In this talk, I discuss theoretical advances in understanding the properties of the Higgs boson and the implications for models of electroweak symmetry breaking. I begin by reviewing some of the recent progress in Standard Model calculations for Higgs boson production and decay rates, followed by a lightning tour of the use of effective field theories in the search for new physics in the Higgs sector. I end with a discussion of the complementarity of precision Higgs coupling measurements and direct searches for heavy particles for the discovery of Beyond the Standard Model physics in the electroweak sector.

   hep-phPoS(2016)·0 citations
3. 03*

   Chiral Magnetic and Vortical Effects in High-Energy Nuclear Collisions --- A Status Report

   D. E. Kharzeev🇺🇸 · J. Liao🇺🇸 · S. A. Voloshin🇺🇸 · G. Wang🇺🇸

   The interplay of quantum anomalies with magnetic field and vorticity results in a variety of novel non-dissipative transport phenomena in systems with chiral fermions, including the quark-gluon plasma. Among them is the Chiral Magnetic Effect (CME) -- the generation of electric current along an external magnetic field induced by chirality imbalance. Because the chirality imbalance is related to the global topology of gauge fields, the CME current is topologically protected and hence non-dissipative even in the presence of strong interactions. As a result, the CME and related quantum phenomena affect the hydrodynamical and transport behavior of strongly coupled quark-gluon plasma, and can be studied in relativistic heavy ion collisions where strong magnetic fields are created by the colliding ions. Evidence for the CME and related phenomena has been reported by the STAR Collaboration at Relativistic Heavy Ion Collider at BNL, and by the ALICE Collaboration at the Large Hadron Collider at CERN. The goal of the present review is to provide an elementary introduction into the physics of anomalous chiral effects, to describe the current status of experimental studies in heavy ion physics, and to outline the future work, both in experiment and theory, needed to eliminate the existing uncertainties in the interpretation of the data.

   hep-phcond-mat.str-elhep-thnucl-ex+1PPNP(2016)·837 citations
4. 04*

   Diffusion of dark matter in a hot and dense nuclear environment

   Marina Cermeño🇪🇸 · M. Ángeles Pérez-García🇪🇸 · Joseph Silk🇫🇷

   We calculate the mean free path in a hot and dense nuclear environment for a fermionic dark matter particle candidate in the $\sim$GeV mass range interacting with nucleons via scalar and vector effective couplings. We focus on the effects of density and temperature in the nuclear medium in order to evaluate the importance of the final state blocking in the scattering process. We discuss qualitatively possible implications for opacities in stellar nuclear scenarios, where dark matter may be gravitationally accreted.

   hep-phastro-ph.HEastro-ph.SRnucl-thPRD(2016)·11 citations
5. 05*

   Enhanced Higgs Mass in Compact Supersymmetry

   Kohsaku Tobioka🇮🇱 · Ryuichiro Kitano🇯🇵 · Hitoshi Murayama🇺🇸

   The current LHC results make weak scale supersymmetry difficult due to relatively heavy mass of the discovered Higgs boson and the null results of new particle searches. Geometrical supersymmetry breaking from extra dimensions, Scherk-Schwarz mechanism, is possible to accommodate such situations. A concrete example, the Compact Supersymmetry model, has a compressed spectrum ameliorating the LHC bounds and large mixing in the top and scalar top quark sector with $|A_t|\sim 2m_{\tilde{t}}$ which radiatively raises the Higgs mass. While the zero mode contribution of the model has been considered, in this paper we calculate the Kaluza-Klein tower effect to the Higgs mass. Although such contributions are naively expected to be as small as a percent level for 10 TeV Kaluza-Klein modes, we find the effect significantly enhances the radiative correction to the Higgs quartic coupling by from 10 to 50 %. This is mainly because the top quark wave function is pushed out from the brane, which makes the top mass depend on higher powers in the Higgs field. As a result the Higgs mass is enhanced up to 15 GeV from the previous calculation. We also show the whole parameter space is testable at the LHC run II.

   hep-phJHEP(2016)·5 citations
6. 06*

   Prompt double $J/\psi$ production in proton-proton collisions at the LHC

   S. P. Baranov🇷🇺 · Amir H. Rezaeian🇨🇱

   We provide a detailed study of prompt double $J/\psi$ production within the non-relativistic QCD (NRQCD) framework in proton-proton collisions at the LHC. We confront the recent LHC data with the results obtained at leading-order (LO) in the NRQCD framework within two approaches of the collinear factorization and the $k_T$-factorization. We show that the LHCb data are consistent with the $k_T$-factorized LO NRQCD results. We show that the full LO NRQCD formalism cannot describe the recent CMS data, with about one order of magnitude discrepancy. If the CMS data are confirmed, this indicates rather large higher-order corrections for prompt double $J/\psi$ production. We provide various predictions which can further test the NRQCD-based approach at the LHC in a kinematic region that LO contributions dominate. We also investigate long-range in rapidity double $J/\psi$ correlations. We found no evidence of a ridge-like structure for double $J/\psi$ production in proton-proton collisions at the LHC up to subleading ${\alpha }_s^6$ accuracy.

   hep-phhep-exnucl-thPRD(2016)·35 citations
7. 07*

   Aspects of Supersymmetry after LHC Run I

   Kohsaku Tobioka🇯🇵

   Supersymmetry is a prime candidate for physics beyond the Standard Model because low-energy supersymmetry stabilizes the Higgs mass avoiding fine-tuning and leads to natural electroweak symmetry breaking. However, searches at the Large Hadron Collider (LHC) for supersymmetric particles have not found any signal and give strong limits on mass of gluino and squark. Also, the observed Higgs mass of 125 GeV is not easily accommodated in the minimal supersymmetric Standard Model (MSSM) where one has to rely on the radiative corrections to boost the Higgs mass accompanied with fine-tuning. I study aspects of supersymmetry in light of these LHC results. In this thesis, I focus on the Compact Supersymmetry model based on arXiv:1206.4993 and the Dirac Next-to-MSSM based on arXiv:1308.0792 and investigate them in more detail.

   hep-phhep-ex2 citations
8. 08*

   Searching for Scalar Dark Matter in Atoms and Astrophysical Phenomena: Variation of Fundamental Constants

   Yevgeny V. Stadnik🇦🇺 · Benjamin M. Roberts🇦🇺 · Victor V. Flambaum🇦🇺 · Vladimir A. Dzuba🇦🇺

   We propose to search for scalar dark matter via its effects on the electromagnetic fine-structure constant and particle masses. Scalar dark matter that forms an oscillating classical field produces `slow' linear-in-time drifts and oscillating variations of the fundamental constants, while scalar dark matter that forms topological defects produces transient-in-time variations of the constants of Nature. These variations can be sought for with atomic clock, laser interferometer and pulsar timing measurements. Atomic spectroscopy and Big Bang nucleosynthesis measurements already give improved bounds on the quadratic interaction parameters of scalar dark matter with the photon, electron, and light quarks by up to 15 orders of magnitude, while Big Bang nucleosynthesis measurements provide the first such constraints on the interaction parameters of scalar dark matter with the massive vector bosons.

   hep-phastro-ph.COnucl-thphysics.atom-ph2 citations
9. 09*

   Constraints on $L_{\mu }-L_{\tau }$ interactions at the LHC and beyond

   Fatemeh Elahi🇺🇸 · Adam Martin🇺🇸

   In this paper we examine the constraints dedicated LHC multi lepton searches can place on $Z^{\prime }$ bosons coming from gauged muon number minus tau number, $L_{\mu }-L_{\tau }$. As the $L_{\mu }-L_{\tau }$ gauge boson does not couple to proton constituents or electrons at tree level, the current bounds are fairly loose, especially for $M_{Z^{\prime }}\gtrsim 1\mathrm{GeV}$. For $2m_{\mu }<M_{Z^{\prime }}<M_Z/2$ we develop search strategies using the $pp\to Z\to 4\mu$ channel. The cleanliness of the final state, combined with the fact that $pp\to Z\to 4e$, $Z\to 2e2\mu$ can be used as background control samples, allow us to spot $L_{\mu }-L_{\tau }$ $Z^{\prime }$ with couplings $\mathcal{O}(10^{-3})$ times the Standard Model couplings. For lighter $Z^{\prime }$, we propose the mode $pp\to 2\mu +/E_T$. The presence of missing energy means there is a wider set of backgrounds to consider in this final state, such as Drell-Yan production of leptonically decaying $\tau$ pairs, however we find these can be controlled with careful cuts. Combining the $4\mu$ and $2\mu +/E_T$ modes, we find that with $\sim 3{\text{ab}}^{-1}$ of integrated luminosity we are sensitive to couplings $g_{Z^{\prime }}\gtrsim 0.005g_1$ and $0.5\mathrm{GeV}\le {\mathrm{M}}_{{\mathrm{Z}}^{\prime }}\le 40\mathrm{GeV}$ and $g_{Z^{\prime }}\gtrsim 0.001g_1$ for $M_{Z^{\prime }}<2m_{\mu }$. This region includes the parameter space where $L_{\mu }-L_{\tau }$ models can ameliorate the muon $g-2$ anomaly. We repeat these analyses at a future $e^{+}{e}^{-}$ Z-factory, where we find improved sensitivity. Specifically, given $2.6\mathrm{a}{\mathrm{b}}^{-1}$ of luminosity, we can exclude $g_{Z^{\prime }}\gtrsim 0.001g_1$ for $2m_{\mu }\le M_{Z^{\prime }}\le M_Z/2$.

   hep-phPRD(2016)·33 citations
10. 10*

    Novel QCD Phenomena at JLab

    Stanley J. Brodsky🇺🇸

    The $12$GeV electron beam energy at Jefferson Laboratory provides ideal electroproduction kinematics for many novel tests of QCD in both the perturbative and nonperturbative domains. These include tests of the quark flavor dependence of the nuclear structure functions; measurements of the QCD running coupling at soft scales; measurements of the diffractive deep inelastic structure function; measurements of exclusive contributions to the $T-$ odd Sivers function; the identification of ``odderon" contributions; tests of the spectroscopic and dynamic features of light-front holography, as well as ``meson-nucleon supersymmetry"; the production of open and hidden charm states in the heavy-quark threshold domain; and the production of exotic hadronic states such as pentaquarks, tetraquarks and even octoquarks containing charm quarks. One can also study fundamental features of QCD at JLab$12$ such as the ``hidden color" of nuclear wavefunctions, the ``color transparency" of hard exclusive processes, and the ``intrinsic strangeness and charm" content of the proton wavefunction. I will also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent. I will also present arguments why shadowing and antishadowing phenomena may be incompatible with the momentum and other sum rules for the nuclear parton distribution functions. I will also briefly review new insights into the hadron mass scale, the hadron mass spectrum, the functional form of the QCD coupling in the nonperturbative domain predicted by light-front holography, and how superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons.

    hep-phPoS(2015)·4 citations
11. 11*

    Gauging MSSM global symmetries and SUSY breaking in de Sitter vacuum

    Ignatios Antoniadis🇫🇷 · Rob Knoops🇨🇭

    We elaborate on a recent study of a model of supersymmetry breaking we proposed recently, in the presence of a tunable positive cosmological constant, based on a gauged shift symmetry of a string modulus, external to the Standard Model (SM) sector. Here, we identify this symmetry with a global symmetry of the SM and work out the corresponding phenomenology. A particularly attracting possibility is to use a combination of Baryon and Lepton number that contains the known matter parity and guarantees absence of dimension-four and five operators that violate B and L.

    hep-phhep-thNPB(2016)·3 citations
12. 12*

    Predictions for 5.023 TeV Pb+Pb collisions at the LHC

    H. Niemi🇩🇪 · K. J. Eskola🇫🇮 · R. Paatelainen🇪🇸 · K. Tuominen🇫🇮

    We compute predictions for various low-transverse-momentum bulk observables in $\sqrt{s_{NN}}=5.023$ TeV Pb+Pb collisions at the LHC from the event-by-event next-to-leading-order perturbative-QCD + saturation + viscous hydrodynamics ("EKRT") model. In particular, we consider the centrality dependence of charged hadron multiplicity, flow coefficients of the azimuth-angle asymmetries and correlations of event-plane angles. The centrality dependencies of the studied observables are predicted to be very similar to those at 2.76 TeV, and the magnitudes of the flow coefficients and event-plane angle correlations are predicted to be close to those at 2.76 TeV. The flow coefficients may, however, offer slightly more discriminating power on the temperature dependence of QCD matter viscosity than the 2.76 TeV measurements. Our prediction for the multiplicity in the 0-5\% centrality class, obtained using the two temperature-dependent shear-viscosity-to-entropy ratios that give the best overall fit to RHIC and LHC data is $d{N}_{\mathrm{ch}}/d\eta {|}_{|\eta |\le 0.5}=1876\dots 2046$. We also predict a power-law increase from 200 GeV Au+Au collisions at RHIC to 2.76 and 5.023 TeV Pb+Pb collisions at the LHC, $d{N}_{\mathrm{ch}}/d\eta {|}_{|\eta |\le 0.5}\propto s^{0.164\dots 0.174}$.

    hep-phnucl-thPRC(2016)·107 citations
13. 13*

    Probing Transverse Momentum Dependent Parton Distributions in Charmonium and Bottomonium Production

    Asmita Mukherjee🇮🇳 · Sangem Rajesh🇮🇳

    We propose the study of unpolarized transverse momentum dependent gluon parton distributions as well as the effect of linearly polarized gluons on transverse momentum and rapidity distributions of $J/\psi$ and ${\rm Y}$ production within the framework of transverse momentum dependent factorization employing color evaporation model (CEM) in unpolarized proton-proton collision. We estimate the transverse momentum and rapidity distributions of $J/\psi$ and ${\rm Y}$ at LHCb, RHIC and AFTER energies using TMD evolution formalism.

    hep-phPRD(2016)·36 citations
14. 14*

    The Quark Flavor Violating Higgs Decay $h\to \bar{b}s+b\bar{s}$ in the MSSM

    M.E. Gómez🇪🇸 · S. Heinemeyer🇪🇸 · M. Rehman🇪🇸

    We study the quark flavor violating Higgs-boson decay $h\to \bar{b}s+b\bar{s}$ in the Minimal Supersymmetric Standard Model (MSSM). The decay is analyzed first in a model independent, and in a second step in the minimal flavor violationg (MFV) Constrained MSSM. The experimental constraints from $B$-Physics observables (BPO) and electroweak precision observables (EWPO) are also calculated and imposed on the parameter space. It is shown that in some cases the EWPO restrict the flavor violating parameter space stronger than the BPO. In the model independent analysis values of $\mathcal{O}(10^{-4})$ can be found for $\mathrm{BR}(h\to \bar{b}s+b\bar{s})$. In the MFV CMSSM such results can only be obtained in very restricted parts of the parameter space. The results show that it is not excluded to observe the decay $h\to \bar{b}s+b\bar{s}$ in the MSSM at future $e^{+}{e}^{-}$ colliders.

    hep-phPRD(2016)·15 citations
15. 15*

    Higher order effective interactions and effective bosonized model for 2-N particle states

    Fabio L. Braghin🇧🇷

    In this work, an effective fermion model with particular higher order interactions given by: $I_{II}={\sum }_n^N{g}_{2^n}({\bar{\psi }}_a{\psi }_a{)}^{2^n}$, for finite $N$, is investigated by means of the auxiliary field method by taking into account 2$n$-particle states as proposed in Ref. [1]. The bosonized model was found to exhibit an approximate symmetry when expanded for weak field fluctuations around the mean field solutions. In the present work, the role of the mean field solutions for the corresponding auxiliary fields is investigated. With the integration of fermions, the resulting determinant is expanded in a polynomial boson model in the weak field approximation and the approximate symmetry found for this series does not appear if the boson mean fields are set to zero.

    hep-phhep-thnucl-thEPJ Web Conf.(2016)·0 citations
16. 16*

    On $\gamma N\to \gamma \rho N^{\prime }$ at large $\gamma \rho$ invariant mass

    R. Boussarie🇫🇷 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷

    Photoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We consider the case where the wide angle Compton scattering subprocess $\gamma (q\bar{q})\to \gamma \rho$ factorizes from generalized parton distribution. At dominant twist, separating the transverse (respectively longitudinal) polarization of the $\rho$ meson allows one to get access to chiral-odd (respectively chiral-even) GPDs. This opens a new way to the extraction of these elusive transversity GPDs.

    hep-phhep-exnucl-exnucl-th2 citations
17. 17*

    Calculation of multi-scale, multi-loop integrals using SecDec 3

    S. Borowka🇨🇭

    In these proceedings the publicly available program SecDec is briefly described. Its main virtues and new features are summarized, including suggestions for an optimal usage of the program.

    hep-phActa Phys.Polon.B(2015)·0 citations
18. 18*

    No inverse magnetic catalysis in the QCD hard and soft wall models

    D. Dudal🇧🇪 · D. R. Granado🇧🇷 · T. G. Mertens🇧🇪

    In this paper, we study the influence of an external magnetic field in holographic QCD models where the backreaction is modeled in via an appropriate choice of the background metric. We add a phenomenological soft wall dilaton to incorporate better IR behavior (confinement). Elaborating on previous studies conducted by [JHEP 1505 (2015) 121], we first discuss the Hawking-Page transition, the dual of the deconfinement transition, as a function of the magnetic field. We confirm that the critical deconfinement temperature can drop with the magnetic field. Secondly, we study the quark condensate holographically as a function of the applied magnetic field and demonstrate that this model does not exhibit inverse magnetic catalysis at the level of the chiral transition. The quest for a holographic QCD model that qualitatively describes the inverse magnetic catalysis at finite temperature is thus still open. Throughout this work, we pay special attention to the different holographic parameters and we attempt to fix them by making the link to genuine QCD as close as possible. This leads to several unanticipated and so far overlooked complications (such as the relevance of an additional length scale in the confined geometry) that we discuss in detail.

    ↳ hep-thhep-lathep-phPRD(2016)·93 citations
19. 19*

    Searching for Axion Dark Matter in Atoms: Oscillating Electric Dipole Moments and Spin-Precession Effects

    Benjamin M. Roberts🇦🇺 · Yevgeny V. Stadnik🇦🇺 · Victor V. Flambaum🇦🇺 · Vladimir A. Dzuba🇦🇺

    We propose to search for axion dark matter via the oscillating electric dipole moments that axions induce in atoms and molecules. These moments are produced through the intrinsic oscillating electric dipole moments of nucleons and through the $P,T$-violating nucleon-nucleon interaction mediated by pion exchange, both of which arise due to the axion-gluon coupling, and also directly through the axion-electron interaction. Axion dark matter may also be sought for through the spin-precession effects that axions produce by directly coupling to fermion spins.

    ↳ physics.atom-phhep-phnucl-th2 citations
20. 20*

    Analysis of recent CLAS data on ${\Sigma }^{\ast }(1385)$ photoproduction off a neutron target

    Xiao-Yun Wang🇨🇳 · Jun He🇨🇳 · Helmut Haberzettl🇺🇸

    Based on recent experimental data obtained by the CLAS Collaboration, the $\Sigma (1385)$ photoproduction off a neutron target at laboratory photon energies $E_{\gamma }$ up to 2.5\,GeV is investigated in an effective Lagrangian approach including $s$-, $u$-, and $t$-channel Born-term contributions. The present calculation does not take into account any explicit $s$-channel baryon-resonance contributions, however, in the spirit of duality, we include $t$-channel exchanges of mesonic Regge trajectories. The onset of the Regge regime is controlled by smoothly interpolating between Feynman-type single-meson exchanges and full-fledged Regge-trajectory exchanges. Gauge invariance broken by the Regge treatment is fully restored by introducing contact-type interaction currents that result from the implementation of \textit{local} gauge invariance in terms of generalized Ward-Takahashi identities. The cross sections for the $\gamma n\to K^{+}{\Sigma }^{\ast }(1385{)}^{-}$ reaction are calculated and compared with experimental results from the CLAS and LEPS collaborations. Despite its simplicity, the present theoretical approach provides a good description of the main features of the data. However, the parameters fitted to the data show that the gauge-invariance-restoring contact term plays a large role which may point to large contributions from final-state interactions.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·23 citations
21. 21*

    The effective description of non-strange hadrons low-energy electro-weak transitions

    Gevorg G. Bunatian🇷🇺

    Starting with the general principles of global and local symmetries, the effective pion-nucleon lagrangian, essentially non-linear in pion field, to describe the non-strange hadrons low-energy electro-weak transitions is developed. We encounter no divergence summarizing properly all the infinite power series in pion field which occur in the course of treatment. Our consistent approach proves to be relevant in considering P-parity violation in pion-nucleon interactions.

    ↳ nucl-thhep-phJ.Phys.G(2018)·1 citation
22. 22*

    Proton structure in the hyperfine splitting of muonic hydrogen

    Franziska Hagelstein🇩🇪 · Vladimir Pascalutsa (KPH, JGU Mainz)🇩🇪

    We present the leading-order prediction of baryon chiral perturbation theory for the proton polarizability contribution to the 2S hyperfine splitting in muonic hydrogen, and compare with the results of dispersive calculations.

    ↳ nucl-thhep-phphysics.atom-phPoS(2016)·26 citations
23. 23*

    Template Composite Dark Matter : SU(2) gauge theory with 2 fundamental flavours

    Vincent Drach🇩🇰 · Ari Hietanen🇩🇰 · Claudio Pica🇩🇰 · Jarno Rantaharju🇩🇰 · Francesco Sannino🇩🇰

    We present a non perturbative study of SU(2) gauge theory with two fundamental Dirac flavours. We discuss how the model can be used as a template for composite Dark Matter (DM). We estimate one particular interaction of the DM candidate with the Standard Model : the interaction through photon exchange computing the electric polarizability of the DM candidate. Finally, we briefly discuss the viability of the model given the present experimental constraints.

    ↳ hep-lathep-phPoS(2016)·19 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.