Wed·May 18, 2016Wednesday·May 18, 2016

1. 01*

   Constraining minimal anomaly free $\mathrm{U}(1)$ extensions of the Standard Model

   Andreas Ekstedt🇸🇪 · Rikard Enberg🇸🇪 · Gunnar Ingelman🇸🇪 · Johan Löfgren🇸🇪 · Tanumoy Mandal🇸🇪

   We consider a class of minimal anomaly free $\mathrm{U}(1)$ extensions of the Standard Model with three generations of right-handed neutrinos and a complex scalar. Using electroweak precision constraints, new 13 TeV LHC data, and considering theoretical limitations such as perturbativity, we show that it is possible to constrain a wide class of models. By classifying these models with a single parameter, $\kappa$, we can put a model independent upper bound on the new $\mathrm{U}(1)$ gauge coupling $g_z$. We find that the new dilepton data puts strong bounds on the parameters, especially in the mass region $M_{Z^{\prime }}\lesssim 3\mathrm{TeV}$.

   hep-phJHEP(2016)·41 citations
2. 02*

   The physics of neutrino cross sections: theoretical studies

   Luis Alvarez-Ruso🇪🇸

   The present status of neutrino cross section physics is reviewed focusing on the recent theoretical developments in quasielastic scattering, multi-nucleon contributions to the inclusive scattering and pion production on nucleons and nuclei. A good understanding of these processes is crucial to meet the precision needs of neutrino oscillation experiments. Some of the challenges that arise in the consistent description of MiniBooNE and MINERvA recent data are discussed.

   hep-phhep-exnucl-th0 citations
3. 03*

   Distributions for tau neutrino interactions observed through the decay $\tau \to \mu {\nu }_{\tau }{\bar{\nu }}_{\mu }$

   I. Alikhanov🇷🇺 · E. A. Paschos🇩🇪

   We investigate the problem of identifying ${\nu }_{\tau }$-induced reactions in large neutrino telescopes. We concentrate on events with tracks and showers where the respective energies $E_{\mu }$ and $E_X$ are measured separately. Then we compute analytically and numerically event distributions in two variables $r_l=E_X/E_l$ and $y^{\prime }=E_{\text{X}}/(E_{\mu }+E_X)$. We find that the $y^{\prime }$-distribution is especially useful because in the ${\nu }_{\tau }$-induced reactions the distribution has a minimum at $y^{\prime }=0.75$ and then increases as $y^{\prime }\to 1$. This is different in ${\nu }_{\mu }$-induced reactions where the $y^{\prime }$-distribution decreases monotonically. The results are demonstrated with figures where one can estimate the required sensitivity of the experiments. Another attractive property is that in several ratios the neutrino flux factorizes and drops out. We hope the results of this article will be useful for searches of tau (anti)neutrinos of energies above 100 GeV to several TeV in the present and planned large volume neutrino telescopes.

   hep-phPLB(2017)·5 citations
4. 04*

   Doubly cvharged vector leptons and the Higgs portal

   Wenjun Li🇨🇳 · J.N.Ng🇨🇦

   Using a bottom up phenomenological approach we constructed a simple doubly charged vector lepton $E^{\pm \pm }$ model for the possible 750 GeV diphoton resonance $\Phi$ at the LHC assuming it to be a scalar particle. Since no stable doubly charged leptons are seen, to facilitate their decays we complete the model by adding a charged SM electroweak scalar $S^{\pm }$. $\Phi$ is a SM singlet and can be either an inert scalar or a Higgs field. In the inert case more than one vector lepton are required to account for the photon fusion production of the resonance if the model is to remain perturbative. For a Higgssed case $S^{\pm }$ can assist the production mechanism without using more than one such lepton. We also found that precision measurements constrain the couplings of $E^{\pm \pm }$ and $S^{\pm }$ to SM particles to be small. This raises the possibility that they can be fairly long lived and can give rise to displaced vertices if produced at the LHC.

   hep-phPRD(2016)·4 citations
5. 05*

   Nonstandard Neutrino Interactions in Supernovae

   Charles J. Stapleford🇺🇸 · Daavid J. Väänänen🇺🇸 · James P. Kneller🇺🇸 · Gail C. McLaughlin🇺🇸 · Brandon T. Shapiro🇺🇸

   Nonstandard interactions (NSI) of neutrinos with matter can significantly alter neutrino flavor evolution in supernovae with the potential to impact explosion dynamics, nucleosynthesis, and the neutrinos signal. In this paper, we explore, both numerically and analytically, the landscape of neutrino flavor transformation effects in supernovae due to NSI and find a new, heretofore unseen transformation processes can occur. These new transformations can take place with NSI strengths well below current experimental limits. Within a broad swath of NSI parameter space, we observe symmetric and standard matter-neutrino resonances for supernovae neutrinos, a transformation effect previously only seen in compact object merger scenarios; in another region of the parameter space we find the NSI can induce neutrino collective effects in scenarios where none would appear with only the standard case of neutrino oscillation physics; and in a third region the NSI can lead to the disappearance of the high density Mikheyev-Smirnov-Wolfenstein resonance. Using a variety of analytical tools, we are able to describe quantitatively the numerical results allowing us to partition the NSI parameter according to the transformation processes observed. Our results indicate nonstandard interactions of supernova neutrinos provide a sensitive probe of beyond the Standard Model physics complementary to present and future terrestrial experiments.

   hep-phastro-ph.HEPRD(2016)·49 citations
6. 06*

   You can hide but you have to run: direct detection with vector mediators

   Francesco D'Eramo🇺🇸 · Bradley J. Kavanagh🇫🇷 · Paolo Panci🇫🇷

   We study direct detection in simplified models of Dark Matter (DM) in which interactions with Standard Model (SM) fermions are mediated by a heavy vector boson. We consider fully general, gauge-invariant couplings between the SM, the mediator and both scalar and fermion DM. We account for the evolution of the couplings between the energy scale of the mediator mass and the nuclear energy scale. This running arises from virtual effects of SM particles and its inclusion is not optional. We compare bounds on the mediator mass from direct detection experiments with and without accounting for the running. In some cases the inclusion of these effects changes the bounds by several orders of magnitude, as a consequence of operator mixing which generates new interactions at low energy. We also highlight the importance of these effects when translating LHC limits on the mediator mass into bounds on the direct detection cross section. For an axial-vector mediator, the running can alter the derived bounds on the spin-dependent DM-nucleon cross section by a factor of two or more. Finally, we provide tools to facilitate the inclusion of these effects in future studies: general approximate expressions for the low energy couplings and a public code runDM to evolve the couplings between arbitrary energy scales.

   hep-phastro-ph.COhep-exJHEP(2016)·119 citations
7. 07*

   Sudakov effects in photon-initiated processes

   L. A. Harland-Lang🇬🇧 · M. G. Ryskin🇷🇺 · V. A. Khoze🇬🇧

   We consider the effect of the Sudakov factor in photon-initiated processes, corresponding to the no branching probability for the initial-state photon. We demonstrate how such a factor follows simply from the solution of the DGLAP equation for the photon PDF, and is therefore included automatically by this. We use this result to argue that the appropriate scale for the QED coupling $\alpha$ associated with an initial-state photon is not the virtuality of the photon, but rather the factorization scale at which the photon PDF is evaluated, and therefore that the use of the on-shell renormalization scheme is not appropriate for such processes. We also discuss exclusive photon-initiated processes, and demonstrate that no explicit Sudakov factor is required in this case.

   hep-phPLB(2016)·28 citations
8. 08*

   Singlet Model Interference Effects with High Scale UV Physics

   S. Dawson🇺🇸 · I. M. Lewis🇺🇸

   One of the simplest extensions of the Standard Model (SM) is the addition of a scalar gauge singlet, S. If S is not forbidden by a symmetry from mixing with the Standard Model Higgs boson, the mixing will generate non-SM rates for Higgs production and decays. In general, there could also be unknown high energy physics that generates additional effective low energy interactions. We show that interference effects between the scalar resonance of the singlet model and the effective field theory (EFT) operators can have significant effects in the Higgs sector. We examine a non-$Z_2$ symmetric scalar singlet model and demonstrate that a fit to the 125 GeV Higgs boson couplings and to limits on high mass resonances, S, exhibit an interesting structure and possible large cancellations of effects between the resonance contribution and the new EFT interactions, that invalidate conclusions based on the renormalizable singlet model alone.

   hep-phPRD(2017)·21 citations
9. 09*

   Polarization and dilepton anisotropy in pion-nucleon collisions

   Enrico Speranza🇩🇪 · Miklós Zétényi🇭🇺 · Bengt Friman🇩🇪

   Hadronic polarization and the related anisotropy of the dilepton angular distribution are studied for the reaction $\pi N\to N{e}^{+}{e}^{-}$. We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the $N(1520)$ and $N(1440)$ resonances, which are essential at the collision energy of the recent data obtained by the HADES collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unravelling the resonance contributions to this process.

   hep-phnucl-thPLB(2017)·19 citations
10. 10*

    Simple Cosmological Solution to the Higgs Instability Problem in the Chaotic Inflation and Formation of Primordial Black Holes

    Masahiro Kawasaki🇯🇵 · Kyohei Mukaida🇯🇵 · Tsutomu T. Yanagida🇯🇵

    We revisit the compatibility between the chaotic inflation, which provides a natural solution to the initial condition problem, and the metastable electroweak vacuum, which is suggested by the results of LHC and the current mass measurements of top quark and Higgs boson. It is known that the chaotic inflation poses a threat to the stability of the electroweak vacuum because it easily generates large Higgs fluctuations during inflation or preheating and triggers the catastrophic vacuum decay. In this paper, we propose a simple cosmological solution in which the vacuum is stabilized during chaotic inflation, preheating and after that. This simple solution naturally predicts the formation of primordial black holes. We find interesting parameter regions where the present dark matter density is provided by them. Also, the thermal leptogenesis can be accommodated in our scenario.

    hep-phastro-ph.COPRD(2016)·23 citations
11. 11*

    Top Pair Production with a jet with NLO QCD off-shell effects

    Malgorzata Worek🇩🇪

    A brief summary of the recent next-to-leading order QCD calculation for e+ ve mu- v_mu bb~ j at the LHC is given. Our computation includes all non-resonant contributions, off-shell effects and interferences for top-quarks and W gauge bosons. Some results for integrated and differential cross sections are shown for the LHC Run1 energy of 8 TeV. A significant reduction of the scale dependence is observed, which indicates that the perturbative expansion is well under control. The results are obtained in the framework of the HELAC-NLO system.

    hep-ph2 citations
12. 12*

    What do we know about neutrinoless double-beta decay nuclear matrix elements?

    J. Menéndez🇯🇵

    The detection of neutrinoless double-beta decay will establish the Majorana nature of neutrinos. In addition, if the nuclear matrix elements of this process are reliably known, the experimental lifetime will provide precious information about the absolute neutrino masses and hierarchy. I review the status of nuclear structure calculations for neutrinoless double-beta decay matrix elements, and discuss some key issues to be addressed in order to meet the demand for accurate nuclear matrix elements.

    hep-phhep-exnucl-exnucl-th7 citations
13. 13*

    Direct Detection of Exothermic Dark Matter with Light Mediator

    Chao-Qiang Geng🇨🇳 · Da Huang🇹🇼 · Chun-Hao Lee🇹🇼 · Qing Wang🇨🇳

    We study the dark matter (DM) direct detection for the models with the effects of the isospin-violating couplings, exothermic scatterings, and/or the lightness of the mediator, proposed to relax the tension between the CDMS-Si signals and null experiments. In the light of the new updates of the LUX and CDMSlite data, we find that many of the previous proposals are now ruled out, including the Ge-phobic exothermic DM model and the Xe-phobic DM one with a light mediator. We also examine the exothermic DM models with a light mediator but without the isospin violation, and we are unable to identify any available parameter space that could simultaneously satisfy all the experiments. The only models that can partially relax the inconsistencies are the Xe-phobic exothermic DM models with or without a light mediator. But even in this case, a large portion of the CDMS-Si regions of interest has been constrained by the LUX and SuperCDMS data.

    hep-phhep-exJCAP(2016)·13 citations
14. 14*

    Remarks on the $P_c$ structures and triangle singularities

    Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪 · Juan Nieves🇪🇸 · Zhi Yang🇩🇪

    It was proposed that the narrow $P_c(4450)$ structure observed by the LHCb Collaboration in the reaction ${\Lambda }_b\to J/\psi pK$ might be due to a triangle singularity around the ${\chi }_{c1}$--proton threshold at 4.45~GeV. We discuss the occurrence of a similar triangle singularity in the $J/\psi p$ invariant mass distribution for the decay ${\Lambda }_b\to J/\psi p\pi$, which could explain the bump around 4.45~GeV in the data. More precise measurements of this process would provide valuable information towards an understanding of the $P_c$ structures.

    hep-phhep-exEPJA(2016)·93 citations
15. 15*

    New Class of SO(10) Models for Flavor

    K.S. Babu🇺🇸 · Borut Bajc🇸🇮 · Shaikh Saad🇺🇸

    We present a new class of unified models based on SO(10) symmetry which provides insights into the masses and mixings of quarks and leptons, including the neutrinos. The key feature of our proposal is the absence of Higgs boson 10_H belonging to the fundamental representation that is normally employed. Flavor mixing is induced via vector-like fermions in the 16 + 16-bar representation. A variety of scenarios, both supersymmetric and otherwise, are analyzed involving a 126_H along with either a 45_H or a 210_H of Higgs boson employed for symmetry breaking. It is shown that this framework, with only a limited number of parameters, provides an excellent fit to the full fermion spectrum, utilizing either type-I or type-II seesaw mechanism. These flavor models can be potentially tested and distinguished in their predictions for proton decay branching ratios, which are analyzed.

    hep-phPRD(2016)·33 citations
16. 16*

    Low-energy limit of the extended Linear Sigma Model

    Florian Divotgey🇩🇪 · Peter Kovacs🇭🇺 · Francesco Giacosa🇩🇪 · Dirk H. Rischke🇩🇪

    The extended Linear Sigma Model (eLSM) is an effective hadronic model based on the linear realization of chiral symmetry $SU(N_f{)}_L\times SU(N_f{)}_R$, with (pseudo)scalar and (axial-)vector mesons as degrees of freedom. In this paper, we study the low-energy limit of the eLSM for $N_f=2$ flavors by integrating out all fields except for the pions, the (pseudo-)Nambu--Goldstone bosons of chiral symmetry breaking. We only keep terms entering at tree level and up to fourth order in powers of derivatives of the pion fields. Up to this order, there are four low-energy coupling constants in the resulting low-energy effective action. We show that the latter is formally identical to Chiral Perturbation Theory (ChPT), after choosing a representative for the coset space generated by chiral symmetry breaking and expanding up to fourth order in powers of derivatives of the pion fields. Two of the low-energy coupling constants of the eLSM are uniquely determined by a fit to hadron masses and decay widths. We find that their tree-level values are in reasonable agreement with the corresponding low-energy coupling constants of ChPT. The other two low-energy coupling constants are functions of parameters that can in principle be determined by $\pi \pi$ scattering, which has not yet been studied within the eLSM. Therefore, we use the respective values from ChPT to make a prediction for the values of these parameters in the eLSM Lagrangian.

    hep-phhep-thEPJA(2018)·21 citations
17. 17*

    Mapping chiral symmetry breaking in the excited baryon spectrum

    Pedro Bicudo🇵🇹 · Marco Cardoso🇵🇹 · Felipe J. Llanes-Estrada🇪🇸 · Tim Van Cauteren🇪🇸

    We study the conjectured "Insensitivity to Chiral Symmetry Breaking" in the highly excited light baryon spectrum. While the experimental spectrum is being measured at JLab and CBELSA/TAPS, this insensitivity remains to be computed theoretically in detail. As the only existing option to have both confinement, highly excited states and chiral symmetry, we adopt the truncated Coulomb gauge formulation of QCD, considering a linearly confining Coulomb term. Adopting a systematic and numerically intensive variational treatment up to 12 harmonic oscillator shells we are able to access several angular and radial excitations. We compute both the excited spectra of $I=1/2$ and $I=3/2$ baryons, up to large spin $J=13/2$, and study in detail the proposed chiral multiplets. While the static-light and light-light spectra clearly show chiral symmetry restoration high in the spectrum, the realization of chiral symmetry is more complicated in the baryon spectrum than earlier expected.

    hep-phPRD(2016)·16 citations
18. 18*

    Probing Higgs-Portal Dark Matter with Weakly Interacting Mediators

    Susanne Westhoff🇩🇪

    The hypothesis of dark matter interacting with the standard model uniquely via the Higgs portal is severely challenged by experiments. However, if dark matter is a fermion, the Higgs-portal interaction implies the presence of mediators, which can change the phenomenology significantly. This article discusses the impact of weakly-interacting mediators on the dark-matter relic abundance, direct detection, and collider searches. At the LHC, a typical signature of Higgs-portal fermion dark matter features soft leptons and missing energy, similarly to gaugino production in models with supersymmetry. We suggest to re-interpret existing gaugino searches in the context of Higgs-portal models and to extend future searches to the broader class of dark sectors with weakly-interacting fermions.

    hep-phhep-ex3 citations
19. 19*

    Two Photon Exchange in Impact Parameter Space in the Relativistic Eikonal Approximation for Elastic e - N Scattering

    Tareq Alhalholy🇺🇸 · Roman Höllwieser🇺🇸

    Using the relativistic Eikonal approximation, we study the one and two photon exchange amplitudes in elastic electron-nucleon scattering for the case of transversely polarized nucleons with unpolarized electrons beam. In our approach, we utilize the convolution theory of Fourier transforms and the transverse charge density in transverse momentum space to evaluate the one and two photon exchange Eikonal amplitudes. The results obtained for the $2\gamma$ amplitude in impact parameter space are compared to the corresponding 4D case. We show that while the one and two photon cross sections are azimuthally symmetric, the interference term between them is azimuthally asymmetric, which is an indication of an azimuthal single spin asymmetry for proton and neutron which can be attributed to the fact that the nucleon charge density is transversely (azimuthally) distorted in the transverse plane for transversely polarized nucleons. In addition, the calculations of the interference term for proton and neutron show agreement in sign and magnitude of the existence data and calculations for transverse target single spin asymmetry.

    hep-ph0 citations
20. 20*

    A History of Dark Matter

    Gianfranco Bertone🇳🇱 · Dan Hooper🇺🇸

    Although dark matter is a central element of modern cosmology, the history of how it became accepted as part of the dominant paradigm is often ignored or condensed into a brief anecdotical account focused around the work of a few pioneering scientists. The aim of this review is to provide the reader with a broader historical perspective on the observational discoveries and the theoretical arguments that led the scientific community to adopt dark matter as an essential part of the standard cosmological model.

    ↳ astro-ph.COastro-ph.GAastro-ph.HEhep-phRMP(2018)·1678 citations
21. 21*

    Very Special Relativity as a background field theory

    Anton Ilderton🇸🇪

    We consider violation of Lorentz invariance in QED induced by a very high frequency background wave. An effective theory is obtained by averaging observables over the rapid field oscillations. This preserves Ward identities and restores translation invariance below the high frequency scale, but only partial Lorentz invariance: we show that the effective theory is C-invariant SIM(2)-QED in Very Special Relativity. Averaging generates the nonlocal terms familiar from SIM(2) theories, while the short-distance behaviour of the background field fermion propagator generates the infinite number of higher-order vertices of SIM(2)-QED.

    ↳ hep-thhep-phPRD(2016)·13 citations
22. 22*

    Productions of J/psi mesons in p-Pb collisions at 5 TeV

    Fu-Hu Liu🇨🇳 · Hai-Ling Lao🇨🇳 · Roy A. Lacey🇺🇸

    The rapidity distributions of $J/\psi$ mesons produced in proton-lead ($p$-Pb) collisions at center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=5$ TeV are studied by using a multisource thermal model and compared with the experimental data of the LHCb and ALICE Collaborations. Correspondingly, the pseudorapidity distributions are accurately obtained from the parameters extracted from the rapidity distributions. At the same time, the transverse momentum distributions in the same experiments are described by the simplest Erlang distribution which is the folding result of two exponential distributions which are contributed by the target and projectile partons respectively.

    ↳ nucl-thhep-exhep-phnucl-exIJMPE(2016)·3 citations
23. 23*

    Anisotropy of Low Energy Direct Photons in Relativistic Heavy Ion Collisions

    T. Koide🇧🇷 · T. Kodama🇧🇷

    We investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions using the Wigner function approach for electromagnetic radiation fields. The angular distribution reveals the information of the initial geometric configurations. Such a property is reflected in the anisotropic parameter $v_2$, showing an increasing $v_2$ as energy decreases, which is a behavior qualitatively different from $v_2$ from hadrons produced in the collisions.

    ↳ nucl-thhep-exhep-phJ.Phys.G(2016)·14 citations
24. 24*

    How to calculate dark matter direct detection exclusion limits that are consistent with gamma rays from annihilation in the Milky Way halo

    David G. Cerdeno🇬🇧 · Mattia Fornasa🇳🇱 · Anne M. Green🇬🇧 · Miguel Peiro🇪🇸

    When comparing constraints on the Weakly Interacting Massive Particle (WIMP) properties from direct and indirect detection experiments it is crucial that the assumptions made about the dark matter (DM) distribution are realistic and consistent. For instance, if the Fermi-LAT Galactic centre GeV gamma-ray excess was due to WIMP annihilation, its morphology would be incompatible with the Standard Halo Model that is usually used to interpret data from direct detection experiments. In this article, we calculate exclusion limits from direct detection experiments using self-consistent velocity distributions, derived from mass models of the Milky Way where the DM halo has a generalized NFW profile. We use two different methods to make the mass model compatible with a DM interpretation of the Galactic centre gamma-ray excess. Firstly, we fix the inner slope of the DM density profile to the value that best fits the morphology of the excess. Secondly, we allow the inner slope to vary and include the morphology of the excess in the data sets used to constrain the gravitational potential of the Milky Way. The resulting direct detection limits differ significantly from those derived using the Standard Halo Model, in particular for light WIMPs, due to the differences in both the local DM density and velocity distribution.

    ↳ astro-ph.COhep-phPRD(2016)·13 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.