Tue·Sep 8, 2015Tuesday·September 8, 2015

1. 01*

   Inverse Amplitude Method for Perturbative Electroweak Symmetry Breaking Sector: The Singlet Higgs Portal as a Study Case

   Tyler Corbett (YITP, Stony Brook & Melbourne U.)🇦🇺 · O. J. P. Éboli (Sao Paulo U.)🇧🇷 · M. C. Gonzalez-Garcia (ICREA, Barcelona & Barcelona U., ECM & YITP, Stony Brook)🇪🇸

   We explore the use of the Inverse Amplitude Method for unitarization of scattering amplitudes to derive the existence and properties of possible new heavy states associated with perturbative extensions of the electroweak breaking sector of the Standard Model starting from the low energy effective theory. We use a toy effective theory generated by integrating out a heavy singlet scalar and compare the pole mass and width of the unitarized amplitudes with those of the original model. Our results show that the Inverse Amplitude Method reproduces correctly the singlet mass up to factors of O(1-3), but its width is overestimated.

   hep-phPRD(2016)·29 citations
2. 02*

   Global constraints on vector-like WIMP effective interactions

   Mattias Blennow🇸🇪 · Pilar Coloma🇺🇸 · Enrique Fernandez-Martinez🇪🇸 · Pedro A. N. Machado🇪🇸 · Bryan Zaldivar🇧🇪

   In this work we combine information from relic abundance, direct detection, cosmic microwave background, positron fraction, gamma rays, and colliders to explore the existing constraints on couplings between Dark Matter and Standard Model constituents when no underlying model or correlation is assumed. For definiteness, we include independent vector-like effective interactions for each Standard Model fermion. Our results show that low Dark Matter masses below 20 GeV are disfavoured at the $3\sigma$ level with respect to higher masses, due to the tension between the relic abundance requirement and upper constraints on the Dark Matter couplings. Furthermore, large couplings are typically only allowed in combinations which avoid effective couplings to the nuclei used in direct detection experiments.

   hep-phastro-ph.HEJCAP(2016)·8 citations
3. 03*

   Higgs-Strahlung: Merging the NLO Drell-Yan and Loop-Induced 0+1 jet Multiplicities

   Dorival Goncalves🇬🇧 · Frank Krauss🇬🇧 · Silvan Kuttimalai🇬🇧 · Philipp Maierhöfer🇬🇧

   We analyse the production of a Higgs boson in association with a Z boson at hadron colliders in the Standard Model and some simple extensions. We show how multi-jet merging algorithms at leading and next-to-leading order for the loop-induced gluon fusion and the Drell-Yan like quark-induced processes, respectively, improve the descriptions for various differential distributions, in particular those that involve the production of additional jets. The phenomenological studies focus on two relevant channels of Higgs boson decays, namely $H\to invisible$ and $H\to b\bar{b}$. We find sizable and phenomenologically relevant corrections to the transverse momentum and invariant mass distributions for the Higgs boson candidate. Thanks to the large destructive interference for the top Yukawa terms, this process is very sensitive to the magnitude and sign of a possible non-standard top-Higgs coupling. We analyse the impact of this anomalous interaction on distributions and estimate constraints from LHC Run II.

   hep-phPRD(2015)·44 citations
4. 04*

   Direct Detection of sub-GeV Dark Matter with Semiconductor Targets

   Rouven Essig🇺🇸 · Marivi Fernandez-Serra🇺🇸 · Jeremy Mardon🇺🇸 · Adrian Soto🇺🇸 · Tomer Volansky🇮🇱 · Tien-Tien Yu🇺🇸

   Dark matter in the sub-GeV mass range is a theoretically motivated but largely unexplored paradigm. Such light masses are out of reach for conventional nuclear recoil direct detection experiments, but may be detected through the small ionization signals caused by dark matter-electron scattering. Semiconductors are well-studied and are particularly promising target materials because their $\mathcal{O}(1\mathrm{eV})$ band gaps allow for ionization signals from dark matter as light as a few hundred keV. Current direct detection technologies are being adapted for dark matter-electron scattering. In this paper, we provide the theoretical calculations for dark matter-electron scattering rate in semiconductors, overcoming several complications that stem from the many-body nature of the problem. We use density functional theory to numerically calculate the rates for dark matter-electron scattering in silicon and germanium, and estimate the sensitivity for upcoming experiments such as DAMIC and SuperCDMS. We find that the reach for these upcoming experiments has the potential to be orders of magnitude beyond current direct detection constraints and that sub-GeV dark matter has a sizable modulation signal. We also give the first direct detection limits on sub-GeV dark matter from its scattering off electrons in a semiconductor target (silicon) based on published results from DAMIC. We make available publicly our code, QEdark, with which we calculate our results. Our results can be used by experimental collaborations to calculate their own sensitivities based on their specific setup. The searches we propose will probe vast new regions of unexplored dark matter model and parameter space.

   hep-phastro-ph.COJHEP(2016)·563 citations
5. 05*

   Pati-Salam Unification from Non-commutative Geometry and the TeV-scale $W_R$ boson

   Ufuk Aydemir🇸🇪 · Djordje Minic🇺🇸 · Chen Sun🇺🇸 · Tatsu Takeuchi🇺🇸

   We analyze the compatibility of the unified left-right symmetric Pati-Salam models motivated by non-commutative geometry and the TeV scale right-handed W boson suggested by recent LHC data. We find that the unification/matching conditions place conflicting demands on the symmetry breaking scales and that generating the required W_R mass and coupling is non-trivial.

   hep-phhep-thInt.J.Mod.Phys.A(2016)·42 citations
6. 06*

   Thermo-magnetic behavior of the quark-gluon vertex

   Alejandro Ayala🇲🇽 · J. J. Cobos-Martinez🇲🇽 · M. Loewe🇿🇦 · Maria Elena Tejeda-Yeomans🇲🇽 · R. Zamora🇨🇱

   The thermo-magnetic corrections to the quark-gluon vertex in the presence of a weak magnetic field are calculated in the frame of the Hard Thermal Loop approximation. The vertex satisfies a QED-like Ward identity with the quark self-energy calculated within the same approximation. It turns out that only the longitudinal vertex components get modified. The calculation provides a first principles result for the quark anomalous magnetic moment at high temperature in a weak magnetic field. The effective thermo-magnetic quark-gluon coupling shows a decreasing behavior as function of the field strength. This result supports the observation that the behavior of the effective quark-gluon coupling in the presence of a magnetic field is an important ingredient in order to understand the inverse magnetic catalysis phenomenon recently observed in the lattice QCD simulations.

   hep-phNucl.Part.Phys.Proc.(2016)·0 citations
7. 07*

   Vertices of the $D_s^{(\ast )}{D}^{(\ast )}{K}^{\ast }$

   R. Khosravi🇮🇷 · M. Janbazi🇮🇷

   Taking into account the contributions of the quark-quark, quark-gluon, and gluon-gluon condensate corrections, the strong form factors and coupling constants of $D_{s0}^{\ast }{D}_0^{\ast }{K}^{\ast }$, $D_{s}D{K}^{\ast }$, $D_s^{\ast }{D}^{\ast }{K}^{\ast }$, $D_{s1}{D}_1{K}^{\ast }$, $D_s{D}^{\ast }{K}^{\ast }$, and $D_{s0}{D}_1{K}^{\ast }$ vertices are investigated within the three-point QCD sum rules method, without and with the $S{U}_f(3)$ symmetry.

   hep-ph1 citation
8. 08*

   Disappearing Inflaton Potential via Heavy Field Dynamics

   Naoya Kitajima🇯🇵 · Fuminobu Takahashi🇯🇵

   We propose a possibility that the inflaton potential is significantly modified after inflation due to heavy field dynamics. During inflation there may be a heavy scalar field stabilized at a value deviated from the low-energy minimum. As the heavy field moves to the low-energy minimum, the inflaton potential could be significantly modified. In extreme cases, the inflaton potential vanishes and the inflaton becomes almost massless at some time after inflation. Such transition of the inflaton potential has interesting implications for primordial density perturbations, reheating, creation of unwanted relics, dark radiation, and experimental search for light degrees of freedom. To be concrete, we consider a chaotic inflation in supergravity where the inflaton mass parameter is promoted to a modulus field, finding that the inflaton becomes stable after the transition and contributes to dark matter. Another example is the new inflation by the MSSM Higgs field which acquires a large expectation value just after inflation, but it returns to the origin after the transition and settles down at the electroweak vacuum. Interestingly, the smallness of the electroweak scale compared to the Planck scale is directly related to the flatness of the inflaton potential.

   hep-phastro-ph.COhep-thJCAP(2016)·0 citations
9. 09*

   Finite Energy Sum Rules with Legendre Polynomial Kernels

   J. Bordes · J. A. Peñarrocha · Michael J. Baker

   In this note we report about a method to deal with finite energy sum rules. With a reasonable knowledge of the main resonances of the spectrum, the method guarantees that we can find a nice duality matching between the low energy hadronic data and asymptotic QCD at high energies.

   hep-phNucl.Part.Phys.Proc.(2016)·0 citations
10. 10*

    New Constraints on Higgs-portal Scalar Dark Matter

    Huayong Han🇨🇳 · Sibo Zheng🇨🇳

    The simplest Higgs-portal scalar dark matter model, in which a real scalar singlet is added to the standard model, has been revisited, by taking into account the constraints from perturbativity, electroweak vacuum stability in the early Universe, dark matter direct detection, and Higgs invisible decay at the LHC. We show that the {\it resonant mass region} is totally excluded and the {\it high mass region} is reduced to a narrow window $1.1$ ~TeV $\le m_s\le$ $2.55$~ TeV, which is slightly reduced to $1.1$~TeV $\le m_s\le$ $2.0$~ TeV if the perturbativity is further imposed. This {\it high mass range} can be fully detected by the Xenon 1T experiment.

    hep-phastro-ph.COhep-exJHEP(2015)·72 citations
11. 11*

    Binding energy of the $X(3872)$ at unphysical pion masses

    V. Baru🇩🇪 · E. Epelbaum🇩🇪 · A.A. Filin🇩🇪 · J. Gegelia🇩🇪 · A.V. Nefediev🇷🇺

    Chiral extrapolation of the $X(3872)$ binding energy is investigated using the modified Weinberg formulation of chiral effective field theory for the $D{\bar{D}}^{\ast }$ scattering. Given its explicit renormalisability, this approach is particularly useful to explore the interplay of the long- and short-range $D{\bar{D}}^{\ast }$ forces in the $X(3872)$ from studying the light-quark (pion) mass dependence of its binding energy. In particular, the parameter-free leading-order calculation shows that the $X$-pole disappears for unphysical large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higher-order pion-mass-dependent contact interaction can change the slope of the binding energy at the physical point yielding the opposite scenario of a stronger bound $X$ at pion masses larger than its physical value. An important role of the pion dynamics and of the 3-body $D\bar{D}\pi$ effects for chiral extrapolations of the $X$-pole is emphasised. The results of the present study should be of practical value for the lattice simulations since they provide a non-trivial connection between lattice points at unphysical pion masses and the physical world.

    hep-phPRD(2015)·36 citations
12. 12*

    Neutrinoless Double Beta Decay in Type I+II Seesaw Models

    Debasish Borah🇮🇳 · Arnab Dasgupta🇮🇳

    We study neutrinoless double beta decay in left-right symmetric extension of the standard model with type I and type II seesaw origin of neutrino masses. Due to the enhanced gauge symmetry as well as extended scalar sector, there are several new physics sources of neutrinoless double beta decay in this model. Ignoring the left-right gauge boson mixing and heavy-light neutrino mixing, we first compute the contributions to neutrinoless double beta decay for type I and type II dominant seesaw separately and compare with the standard light neutrino contributions. We then repeat the exercise by considering the presence of both type I and type II seesaw, having non-negligible contributions to light neutrino masses and show the difference in results from individual seesaw cases. Assuming the new gauge bosons and scalars to be around a TeV, we constrain different parameters of the model including both heavy and light neutrino masses from the requirement of keeping the new physics contribution to neutrinoless double beta decay amplitude below the upper limit set by the GERDA experiment and also satisfying bounds from lepton flavor violation, cosmology and colliders.

    hep-phJHEP(2015)·33 citations
13. 13*

    nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties

    A. Kusina🇫🇷 · K. Kovarik🇩🇪 · T. Jezo🇮🇹 · D. B. Clark🇺🇸 · C. Keppel🇺🇸 · F. Lyonnet🇺🇸 · J. G. Morfin🇺🇸 · F. I. Olness🇺🇸 · J. F. Owens🇺🇸 · I. Schienbein🇫🇷 · J. Y. Yu🇺🇸

    We present the first official release of the nCTEQ nuclear parton distribution functions with errors. The main addition to the previous nCTEQ PDFs is the introduction of PDF uncertainties based on the Hessian method. Another important addition is the inclusion of pion production data from RHIC that give us a handle on constraining the gluon PDF. This contribution summarizes our results from arXiv:1509.00792 and concentrates on the comparison with other groups providing nuclear parton distributions.

    hep-phPoS(2015)·18 citations
14. 14*

    A Brief Comment on Multi-Gluon Amplitudes and Double Parton Interactions

    Daniele Treleani🇮🇹 · Giorgio Calucci🇮🇹

    A simplest case, where a contribution to a color ordered multi-gluon amplitude, describing a three body partonic interaction, can split into two weakly correlated two-body gluon scattering amplitudes and may thus contribute to a Double Parton Interaction, is briefly discussed. We find that the color ordered amplitude is not enhanced in the typical configuration generated by a DPI, where the transverse momenta of final state gluons are compensated pairwise, while a dominant contribution to the multi-gluon amplitude is due to terms proportional to the fusion amplitude of two initial state gluons. Which corresponds to an amplitude effectively describing a two rather than a three-body partonic interaction.

    hep-ph0 citations
15. 15*

    A faster, high precision algorithm for calculating symmetric and asymmetric $M_{T2}$

    Colin H. Lally

    A new algorithm for calculating the stransverse mass, $M_{T2}$, in either symmetric or asymmetric situations has been developed which exhibits good stability, high precision and quadratic convergence for the majority of the $M_{T2}$ parameter space, leading to up to a factor of ten increase in speed compared to other $M_{T2}$ calculators of comparable precision. This document describes and validates the methodology used by the algorithm, and provides comparisons both in terms of accuracy and speed with other existing implementations.

    hep-ph2 citations
16. 16*

    Electroweak symmetry breaking through bosonic seesaw mechanism in a classically conformal extension of the Standard Model

    Naoyuki Haba🇯🇵 · Hiroyuki Ishida🇯🇵 · Nobuchika Okada🇺🇸 · Yuya Yamaguchi🇯🇵

    We suggest the so-called bosonic seesaw mechanism in the context of a classically conformal $U(1{)}_{B-L}$ extension of the Standard Model with two Higgs doublet fields. The $U(1{)}_{B-L}$ symmetry is radiatively broken via the Coleman-Weinberg mechanism, which also generates the mass terms for the two Higgs doublets through quartic Higgs couplings. Their masses are all positive but, nevertheless, the electroweak symmetry breaking is realized by the bosonic seesaw mechanism. We analyze the renormalization group evolutions for all model couplings, and find that a large hierarchy among the quartic Higgs couplings, which is crucial for the bosonic seesaw mechanism to work, is dramatically reduced toward high energies. Therefore, the bosonic seesaw is naturally realized with only a mild hierarchy, if some fundamental theory, which provides the origin of the classically conformal invariance, completes our model at some high energy, for example, the Planck scale. The requirements for the perturbativity of the running couplings and the electroweak vacuum stability in the renormalization group analysis as well as for the naturalness of the electroweak scale, we have identified the regions of model parameters. For example, the scale of the $U(1{)}_{B-L}$ gauge symmetry breaking is constrained to be $\lesssim 100$ TeV, which corresponds to the extra heavy Higgs boson masses to be $\lesssim 2$ TeV. Such heavy Higgs bosons can be tested at the Large Hadron Collider in the near future.

    hep-ph10 citations
17. 17*

    Limits on sterile neutrino contributions to neutrinoless double beta decay

    J. Barea🇨🇱 · J. Kotila🇺🇸 · F. Iachello🇺🇸

    Nuclear matrix elements (NME) for exchange of arbitrary mass neutrinos are calculated in the interacting boson model (IBM-2). By combining the NME with the phase space factors (PSF), expected half-lives for neutrinos of mass $m_N$ and coupling $U_{eN}$ are estimated. Limits on sterile neutrinos with masses in the eV, keV, MeV-GeV, and TeV range are given.

    hep-phnucl-thPRD(2015)·55 citations
18. 18*

    Addendum: Electroweak Sudakov effects in W, Z and gamma production at large transverse momentum

    Thomas Becher🇨🇭 · Xavier Garcia i Tormo🇨🇭

    In this addendum to Phys. Rev. D 88, no. 1, 013009 (2013), we give results for the electroweak Sudakov corrections in gauge-boson production at large transverse momentum p_T at proton colliders. In order for the results to be easily usable, we provide a simple and accurate parameterization of the corrections as a function of p_T and the center-of-mass energy \sqrt{s}. Additionally, we also discuss the dependence of the electroweak corrections on the rapidity of the produced boson, and comment on the complications that arise in the photon-production case due to isolation requirements

    hep-phhep-exPRD(2015)·17 citations
19. 19*

    Theoretical perspective on rare and radiative charm decays

    Svjetlana Fajfer🇸🇮

    Recent experimental bounds on rare charm decays offer a chance to improve our theoretical understanding of physics present in $c\to u\gamma$ and $c\to u{l}^{+}{l}^{-}$ transitions. Standard Model and New Physics contributions are reviewed for inclusive and exclusive $D\to V\gamma$, $D^{+}\to {\pi }^{+}{l}^{+}{l}^{-}$, $D\to l^{+}{l}^{-}$ decays. Observables important for search of New Physics are discussed. Possibility to observe CP violation in rare charm decays is questioned.

    hep-phhep-ex17 citations
20. 20*

    Probing CPT in transitions with entangled neutral kaons

    J. Bernabeu🇪🇸 · A. Di Domenico🇮🇹 · P. Villanueva-Perez🇪🇸

    In this paper we present a novel CPT symmetry test in the neutral kaon system based, for the first time, on the direct comparison of the probabilities of a transition and its CPT reverse. The required interchange of "in" $\leftrightarrow$ "out" states for a given process is obtained exploiting the Einstein-Podolsky-Rosen correlations of neutral kaon pairs produced at a $\varphi$-factory. The observable quantities have been constructed by selecting the two semileptonic decays for flavour tag, the $\pi \pi$ and $3{\pi }^0$ decays for CP tag and the time orderings of the decay pairs. The interpretation in terms of the standard Weisskopf-Wigner approach to this system, directly connects CPT violation in these observables to the violating $\Re \delta$ parameter in the mass matrix of $K^0$-$\overline{K^0}$, a genuine CPT violating effect independent of $\Delta \Gamma$ and not requiring the decay as an essential ingredient. Possible spurious effects induced by CP violation in the decay and/or a violation of the $\Delta S=\Delta Q$ rule have been shown to be well under control. The proposed test is thus fully robust, and might shed light on possible new CPT violating mechanisms, or further improve the precision of the present experimental limits. It could be implemented at the DA$\Phi$NE facility in Frascati, where the KLOE-2 experiment might reach a statistical sensitivity of $\mathcal{O}(10^{-3})$ on the newly proposed observable quantities.

    hep-phJHEP(2015)·54 citations
21. 21*

    Diboson excess in the Higgs singlet and vector-like quark models

    Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷

    Diboson resonance with mass of $1.8-2$ TeV is reported successively by CMS and ATLAS experiments in proton-proton collisions at $\sqrt{s}=8$ TeV. We investigate the potentiality of Higgs singlet as the TeV resonance. The challenges of low production cross section and high width for a fundamental scalar could be got over by three factors: (1) larger Yukawa couplings, (2) larger number of heavy quarks and (3) smaller mixing angle with standard model Higgs. We find that the required factors could be realized in the framework of two vector-like triplet quarks (VLTQs) and the resulting production cross section and decay fraction of heavy Higgs $\sigma (pp\to H)\times \mathrm{BR}(H\to W^{+}{W}^{-}+ZZ)$ can be of $\mathcal{O}(10)$ fb when masses of new heavy quarks are 1 TeV, the values of Yukawa couplings are around $3$ and the mixing angle is $\sin \theta \sim 0.11$. Furthermore, we study the product of VLTQ-pair production cross section and the BRs of VLTQ decays, and find that the cross sections in the decay channels, such as $u_{4,5}\to b{W}^{+}$, $d_5\to t{W}^{-}$ and $d_4\to bh(Z)$ could be $7-17$ fb at 13 TeV LHC.

    hep-phhep-exPRD(2015)·21 citations
22. 22*

    Effect of coupled channels of the multi-channel pion-pion scattering in two-pion transitions of the ${\rm Y}$ mesons

    Yu.S. Surovtsev🇷🇺 · P. Bydžovský🇨🇿 · T. Gutsche🇩🇪 · R. Kamiński🇵🇱 · V.E. Lyubovitskij🇩🇪 · M. Nagy🇭🇺

    The effect of isoscalar S-wave processes $\pi \pi \to \pi \pi ,K\overline{K},\eta \eta$ is considered in the analysis of data (from the ARGUS, CLEO, CUSB, Crystal Ball, Belle, BABAR collaborations) on the bottomonia decays --- ${\rm Y}(mS)\to {\rm Y}(nS)\pi \pi$ ($m>n,m=2,3,4,5,n=1,2,3$). It is shown that the dipion mass spectra of these decays are explained by the unified mechanism related to the contribution of the multichannel $\pi \pi$ scattering in the final states of these reactions. Since in the analysis the multichannel $\pi \pi$-scattering amplitudes did not change in comparison with the ones in our combined analysis of data on the multichannel $\pi \pi$ scattering and on the charmonia decays --- $J/\psi \to \varphi (\pi \pi ,K\overline{K})$ and $\psi (2S)\to J/\psi (\pi \pi )$ (from the Crystal Ball, DM2, Mark II, Mark III, and BES II) --- the results confirm all our earlier conclusions on the scalar mesons.

    hep-phInt.J.Mod.Phys.Conf.Ser.(2015)·0 citations
23. 23*

    Spin Polarisation of $t\bar{t}\gamma \gamma$ production at NLO+PS with GoSam interfaced to MadGraph5_aMC@NLO

    Hans van Deurzen🇩🇪 · Rikkert Frederix🇩🇪 · Valentin Hirschi🇺🇸 · Gionata Luisoni🇩🇪 · Pierpaolo Mastrolia🇮🇹 · Giovanni Ossola🇺🇸

    We present an interface between the multipurpose NLO Monte Carlo tool MadGraph5_aMC@NLO and the automated one-loop amplitude generator GoSam. As a first application of this novel framework, we compute the NLO corrections to $pp\to t\bar{t}H$ and $pp\to t\bar{t}\gamma \gamma$ matched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.

    hep-phEPJC(2016)·20 citations
24. 24*

    Baryon effects on the location of QCD's critical end point

    Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Christian A. Welzbacher🇩🇪

    The location of the critical end point of QCD has been determined in previous studies of $N_f=2+1$ and $N_f=2+1+1$ dynamical quark flavors using a (truncated) set of Dyson-Schwinger equations for the quark and gluon propagators of Landau-gauge QCD. A source for systematic errors in these calculations has been the omission of terms in the quark-gluon interaction that can be parametrized in terms of baryonic degrees of freedom. These have a potentially large dependence on chemical potential and therefore may affect the location of the critical end point. In this exploratory study we estimate the effects of these contributions, both in the vacuum and at finite temperature and chemical potential. We find only a small influence of baryonic contributions on the location of the critical end point. We estimate the robustness of this result by parameterizing further dependencies on chemical potential.

    hep-phhep-latnucl-thPRD(2016)·90 citations
25. 25*

    Fermion and scalar phenomenology of a 2-Higgs doublet model with $S_3$

    A. E. Cárcamo Hernández🇨🇱 · I. de Medeiros Varzielas🇬🇧 · E. Schumacher🇩🇪

    We propose a 2-Higgs doublet model where the symmetry is extended by $S_3\otimes Z_3\otimes Z_3^{\prime }\otimes Z_{14}$ and the field content is enlarged by extra $SU(2{)}_L$ singlet scalar fields. $S_3$ makes the model predictive and leads to viable fermion masses and mixing. The observed hierarchy of the quark masses arises from the $Z_3^{\prime }$ and $Z_{14}$ symmetries. The light neutrino masses are generated through a type I seesaw mechanism with two heavy Majorana neutrinos. In the lepton sector we obtain mixing angles that are nearly tri-bi-maximal, in an excellent agreement with the observed lepton parameters. The vacuum expectation values required for the model are naturally obtained from the scalar potential, and we analyze the scalar sector properties further constraining the model through the $\gamma \gamma$ decay channel and the $T$ and $S$ parameters.

    hep-phPRD(2016)·52 citations
26. 26*

    Anomalous X-Ray Galactic signal from 7 keV spin-$3/2$ dark matter decay

    Sukanta Dutta🇮🇳 · Ashok Goyal🇮🇳 · Sanjeev Kumar🇮🇳

    In order to explain the recently reported peak at $3.55$ keV in the galactic x-ray spectrum, we propose a simple model. In this model, the Standard Model is extended by including a neutral spin-$3/2$ vector-like fermion that transforms like a singlet under SM gauge group. This $7.1$ keV spin-$3/2$ fermion is considered to comprise a portion of the observed dark matter. Its decay into a neutrino and a photon with decay life commensurate with the observed data, fits the relic dark matter density and obeys the astrophysical constraints from the supernova cooling.

    hep-phJCAP(2016)·9 citations
27. 27*

    Toward an understanding of the $R_{AA}$ and $v_2$ puzzle for heavy quarks

    Francesco Scardina🇮🇹 · Santosh K Das🇮🇹 · Salvatore Plumari🇮🇹 · Jessica I. Bellone🇮🇹 · Vincenzo Greco🇮🇹

    One of the primary aims of the ongoing nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is to create a Quark Gluon Plasma (QGP). The heavy quarks constitutes a unique probe of the QGP properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$ related to heavy quark has been observed which challenged all the existing models.\\ We discuss how the temperature dependence of the heavy quark drag coefficient can address for a large part of such a puzzle. We have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA}(p_T)$ experimentally observed at RHIC energy. We have found that for the same $R_{AA}(p_T)$ one can generate $2-3$ times more $v_2$ depending on the temperature dependence of the heavy quark drag coefficient.

    ↳ nucl-thhep-phNucl.Part.Phys.Proc.(2016)·5 citations
28. 28*

    Transition radiation at radio frequencies from ultra-high energy neutrino-induced showers

    Pavel Motloch🇺🇸 · Jaime Alvarez-Muñiz🇪🇸 · Paolo Privitera🇺🇸 · Enrique Zas🇪🇸

    Coherent radiation at radio frequencies from high-energy showers fully contained in a dense radio-transparent medium - like ice, salt or regolith - has been extensively investigated as a promising technique to search for ultra-high energy (UHE) neutrinos. Additional emission in the form of transition radiation may occur when a neutrino-induced shower produced close to the Earth surface emerges from the ground into atmospheric air. We present the first detailed evaluation of transition radiation from high-energy showers crossing the boundary between two different media. We found that transition radiation is sizable over a wide solid angle and coherent up to $\sim$ 1 GHz. These properties encourage further work to evaluate the potential of a large-aperture UHE neutrino experiment based on detection of transition radiation.

    ↳ astro-ph.HEastro-ph.IMhep-phPRD(2016)·21 citations
29. 29*

    Weak Gravity Conjecture in AdS/CFT

    Yu Nakayama🇺🇸 · Yasunori Nomura🇺🇸

    We study implications of the weak gravity conjecture in the AdS/CFT correspondence. Unlike in Minkowski spacetime, AdS spacetime has a physical length scale, so that the conjecture must be generalized with an additional parameter. We discuss possible generalizations and translate them into the language of dual CFTs, which take the form of inequalities involving the dimension and charge of an operator as well as the current and energy-momentum tensor central charges. We then test these inequalities against various CFTs to see if they are universally obeyed by all the CFTs. We find that certain CFTs, such as supersymmetric QCDs, do not satisfy them even in the large $N$ limit. This does not contradict the conjecture in AdS spacetime because the theories violating them are either unlikely or unclear to have weakly coupled gravitational descriptions, but it suggests that the CFT inequalities obtained here by naive translations do not apply beyond the regime in which weakly coupled gravitational descriptions are available.

    ↳ hep-thgr-qchep-phPRD(2015)·109 citations
30. 30*

    Goldstone Boson Interaction in D=2+1 (Pseudo-)Lorentz-Invariant Systems with a Spontaneously Broken Internal Rotation Symmetry

    Christoph P. Hofmann🇲🇽

    The low-temperature properties of systems characterized by a spontaneously broken internal rotation symmetry, O($N$) $\to$ O($N$-1), are governed by Goldstone bosons and can be derived systematically within effective Lagrangian field theory. In the present study we consider systems living in two spatial dimensions, and evaluate their partition function at low temperatures up to three-loop order. Although our results are valid for any such system, here we use magnetic terminology, i.e., we refer to quantum spin systems. We discuss the sign of the Goldstone boson interaction in the pressure, staggered magnetization, and susceptibility as a function of an external staggered field for general $N$. As it turns out, the $d$=2+1 quantum XY model ($N$=2) and the $d$=2+1 Heisenberg antiferromagnet ($N$=3), are rather special, as they represent the only cases where the spin-wave interaction in the pressure is repulsive in the whole parameter regime where the effective expansion applies. Remarkably, the $d$=2+1 XY model is the only system where the interaction contribution in the staggered magnetization (susceptibility) tends to positive (negative) values at low temperatures and weak external field.

    ↳ cond-mat.str-elhep-phNPB(2016)·7 citations
31. 31*

    Deep Inelastic Scattering in the Exponentially Small Bjorken Parameter Regime from the Holographic Softwall Model

    Eduardo Folco Capossoli🇧🇷 · Henrique Boschi-Filho🇧🇷

    We use the AdS/CFT correspondence and the holographic softwall model to investigate the Deep Inelastic Scattering (DIS) in the exponentially small $x$ (Bjorken Parameter) regime. We calculate the corresponding structure functions for scalar fields. Using these results we studied the problem of the saturation line in the strong interactions. Our results are consistent with those achieved using other models.

    ↳ hep-thhep-phPRD(2015)·15 citations
32. 32*

    Frequentist limit setting in effective field theories

    Kristian Damlund Gregersen🇬🇧 · Jørgen Beck Hansen🇩🇰

    The original frequentist approach for computing confidence intervals involves the construction of the confidence belt which provides a mapping of the observation in data into a subset of values for the parameter. There are different prescriptions for constructing the confidence belt, here we use the one provided by Feldman and Cousins. Alternative methods based on the frequentist idea exist, including the delta likelihood method, the $C{L}_s$ method and a method here referred to as the $p$-value method, which have all been commonly used in high energy experiments. The purpose of this article is to draw attention to a series of potential problems when applying these alternative methods to the important case where the predicted signal depends quadratically on the parameter of interest, a situation which is common in high energy physics as it covers scenarios encountered in effective theories. These include anomalous Higgs couplings and anomalous trilinear and quartic gauge couplings. It is found that the alternative methods, contrary to the original method using the confidence belt, encode the goodness-of-fit into the confidence intervals and potentially over-constrain the parameter.

    ↳ physics.data-anhep-exhep-ph2 citations
33. 33*

    N${}_f$ = 1 QCD in External Magnetic Fields: Staggered Fermions

    Paolo Cea🇮🇹 · Leonardo Cosmai🇮🇹

    We investigate N${}_f$ = 1 QCD in external magnetic fields on the lattice. The background field is introduced by means of the so-called Schrodinger functional. We adopt standard staggered fermions with constant bare mass $am=0.025$ and magnetic fields with constant magnetic flux up to $a^{2}eH\simeq 2.3562$. We find that the the deconfinement and chiral symmetry restoration temperatures do not depend on the strength of the applied magnetic field. Our method allow us to easily study the effects of the external magnetic fields on the QCD thermodynamics. We determine the influences of applied magnetic fields to the free energy, pressure, and equation of state of strongly interacting matter.

    ↳ hep-lathep-phJHEP(2015)·4 citations
34. 34*

    Spectral caustics in laser assisted Breit-Wheeler process

    T. Nousch🇩🇪 · D. Seipt🇩🇪 · B. Kämpfer🇩🇪 · A. I. Titov🇷🇺

    Electron-positron pair production by the Breit-Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering.

    ↳ physics.plasm-phhep-phphysics.opticsquant-phPLB(2016)·25 citations
35. 35*

    The Rethermalizing Bose-Einstein Condensate of Dark Matter Axions

    Nilanjan Banik🇺🇸 · Adam Christopherson🇺🇸 · Pierre Sikivie🇺🇸 · Elisa Maria Todarello🇺🇸

    The axions produced during the QCD phase transition by vacuum realignment, string decay and domain wall decay thermalize as a result of their gravitational self-interactions when the photon temperature is approximately 500 eV. They then form a Bose-Einstein condensate (BEC). Because the axion BEC rethermalizes on time scales shorter than the age of the universe, it has properties that distinguish it from other forms of cold dark matter. The observational evidence for caustic rings of dark matter in galactic halos is explained if the dark matter is axions, at least in part, but not if the dark matter is entirely WIMPs or sterile neutrinos.

    ↳ astro-ph.COhep-ph5 citations
36. 36*

    Inconstant Planck's constant

    Gianpiero Mangano🇮🇹 · Fedele Lizzi🇮🇹 · Alberto Porzio🇮🇹

    Motivated by the Dirac idea that fundamental constant are dynamical variables and by conjectures on quantum structure of spacetime at small distances, we consider the possibility that Planck constant $\hslash$ is a time depending quantity, undergoing random gaussian fluctuations around its measured constant mean value, with variance ${\sigma }^2$ and a typical correlation timescale $\Delta t$. We consider the case of propagation of a free particle and a one--dimensional harmonic oscillator coherent state, and show that the time evolution in both cases is different from the standard behaviour. Finally, we discuss how interferometric experiments or exploiting coherent electromagnetic fields in a cavity may put effective bounds on the value of $\tau ={\sigma }^2\Delta t$.

    ↳ quant-phhep-phhep-thmath-ph+1Int.J.Mod.Phys.A(2015)·28 citations
37. 37*

    Classical Limit of Black Hole Quantum N-Portrait and BMS Symmetry

    Gia Dvali🇩🇪 · Cesar Gomez🇪🇸 · Dieter Lüst🇩🇪

    Black hole entropy, denoted by N, in (semi)classical limit is infinite. This scaling reveals a very important information about the qubit degrees of freedom that carry black hole entropy. Namely, the multiplicity of qubits scales as N, whereas their energy gap and their coupling as 1/N. Such a behavior is indeed exhibited by Bogoliubov-Goldstone degrees of freedom of a quantum-critical state of N soft gravitons (a condensate or a coherent state) describing the black hole quantum portrait. They can be viewed as the Goldstone modes of a broken symmetry acting on the graviton condensate. In this picture Minkowski space naturally emerges as a coherent state of infinite-N gravitons of infinite wavelength and it carries an infinite entropy. In this paper we ask what is the geometric meaning (if any) of the classical limit of this symmetry. We argue that the infinite-N limit of Bogoliubov-Goldstone modes of critical graviton condensate is described by recently-discussed classical BMS super-translations broken by the black hole geometry. However, the full black hole information can only be recovered for finite N, since the recovery time becomes infinite in classical limit in which N is infinite.

    ↳ hep-thgr-qchep-phPLB(2016)·63 citations
38. 38*

    The spectrum of anomalous magnetohydrodynamics

    Massimo Giovannini🇨🇭

    The equations of anomalous magnetohydrodynamics describe an Abelian plasma where conduction and chiral currents are simultaneously present and constrained by the second law of thermodynamics. At high frequencies the magnetic currents play the leading role and the spectrum is dominated by two-fluid effects. The system behaves instead as a single fluid in the low-frequency regime where the vortical currents induce potentially large hypermagnetic fields. After deriving the physical solutions of the generalized Appleton-Hartree equation, the corresponding dispersion relations are scrutinized and compared with the results valid for cold plasmas. Hypermagnetic knots and fluid vortices can be concurrently present at very low frequencies and suggest a qualitatively different dynamics of the hydromagnetic nonlinearities.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2016)·13 citations
39. 39*

    The scenario of two families of compact stars 1. Equations of state, mass-radius relations and binary systems

    Alessandro Drago🇮🇹 · Andrea Lavagno🇮🇹 · Giuseppe Pagliara🇮🇹 · Daniele Pigato🇮🇹

    We present several arguments which favor the scenario of two coexisting families of compact stars: hadronic stars and quark stars. Besides the well known hyperon puzzle of the physics of compact stars, a similar puzzle exists also when considering delta resonances. We show that these particles appear at densities close to twice saturation density and must be therefore included in the calculations of the hadronic equation of state. Such an early appearance is strictly related to the value of the L parameter of the symmetry energy that has been found, in recent phenomenological studies, to lie in the range $40<L<62$ MeV. We discuss also the threshold for the formation of deltas and hyperons for hot and lepton rich hadronic matter. Similarly to the case of hyperons, also delta resonances cause a softening of the equation of state which makes it difficult to obtain massive hadronic stars. Quark stars, on the other hand, can reach masses up to $2.75M_{\odot }$ as predicted by perturbative QCD calculations. We then discuss the observational constraints on the masses and the radii of compact stars. The tension between the precise measurements of high masses and the indications of the existence of very compact stellar objects (with radii of the order of $10$ km) is relieved when assuming that very massive compact stars are quark stars and very compact stars are hadronic stars. Finally, we discuss recent interesting measurements of the eccentricities of the orbits of millisecond pulsars in low mass X-ray binaries. The high values of the eccentricities found in some cases could be explained by assuming that the hadronic star, initially present in the binary system, converts to a quark star due to the increase of its central density.

    ↳ astro-ph.SRhep-phnucl-thEPJA(2016)·114 citations
40. 40*

    The scenario of two families of compact stars 2. Transition from hadronic to quark matter and explosive phenomena

    Alessandro Drago🇮🇹 · Giuseppe Pagliara🇮🇹

    We will follow the two-families scenario described in the accompanying paper, in which compact stars having a very small radius and masses not exceeding about 1.5$M_{\odot }$ are made of hadrons, while more massive compact stars are quark stars. In the present paper we discuss the dynamics of the transition of a hadronic star into a quark star. We will show that the transition takes place in two phases: a very rapid one, lasting a few milliseconds, during which the central region of the star converts into quark matter and the process of conversion is accelerated by the existence of strong hydrodynamical instabilities, and a second phase, lasting about ten seconds, during which the process of conversion proceeds till the surface of the star via production and diffusion of strangeness. We will show that these two steps play a crucial role in the phenomenological implications of the model. We will discuss the possible implications of this scenario both for long and for short Gamma Ray Bursts, using the proto-magnetar model as the reference frame of our discussion. We will show that the process of quark deconfinement can be connected to specific observed features of the GRBs. In the case of long GRBs we will discuss the possibility that quark deconfinement is at the origin of the second peak present in quite a large fraction of bursts. Also we will discuss the possibility that long GRBs can take place in binary systems without being associated with a SN explosion. Concerning short GRBs, quark deconfinement can play the crucial role in limiting their duration. Finally we will shortly revisit the possible relevance of quark deconfinement in some specific type of Supernova explosions, in particular in the case of very massive progenitors.

    ↳ astro-ph.SRhep-phnucl-thEPJA(2016)·84 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.