Wed·Aug 24, 2016Wednesday·August 24, 2016

1. 01*

   Naturally Stable Right-Handed Neutrino Dark Matter

   P. S. Bhupal Dev🇩🇪 · Rabindra N. Mohapatra🇺🇸 · Yongchao Zhang🇧🇪

   We point out that a class of non-supersymmetric models based on the gauge group $SU(3{)}_C\times SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{Y_L}\times U(1{)}_{Y_R}$ possesses an automatic, exact $Z_2$ symmetry under which the fermions in the $SU(2{)}_R\times U(1{)}_{Y_R}$ sector (called $R$-sector) are odd and those in the standard model sector (called $L$-sector) are even. This symmetry, which is different from the usual parity symmetry of the left-right symmetric models, persists in the lepton sector even after the gauge symmetry breaks down to $SU(3{)}_C\times U(1{)}_{\mathrm{EM}}$. This keeps the lightest right-handed neutrino naturally stable, thereby allowing it to play the role of dark matter (DM) in the Universe. There are several differences between the usual left-right models and the model presented here: (i) our model can have two versions, one which has no parity symmetry so that the couplings and masses in the $L$ and $R$ sectors are unrelated, and another which has parity symmetry so that couplings are related; (ii) the $R$-sector fermions are chosen much heavier than the $L$-sector ones in both scenarios; and finally (iii) both light and heavy neutrinos are Majorana fermions with the light neutrino masses arising from a pure type-II seesaw mechanism. We discuss the DM relic density, direct and indirect detection prospects and associated collider signatures of the model. Comparing with current collider and direct detection constraints, we find a lower bound on the DM mass of order of 1 TeV. We also point out a way to relax the DM unitarity bound in our model for much larger DM masses by an entropy dilution mechanism. An additional feature of the model is that the DM can be made very long lived, if desired, by allowing for weak breaking of the above $Z_2$ symmetry. Our model also predicts the existence of long-lived colored particles which could be searched for at the LHC.

   hep-phastro-ph.COJHEP(2016)·49 citations
2. 02*

   Dark matter and the neutrino portal paradigm

   Vannia González-Macías🇺🇸 · José Illana🇪🇸 · José Wudka🇺🇸

   A simple extension of the Standard Model (SM) that provides an explicit realization of the dark-matter (DM) neutrino-portal paradigm is presented. The leading interactions between the dark sector, containing scalars and relic fermions, and the SM involve neutrinos. This model meets all observational constraints.

   hep-phJ.Phys.Conf.Ser.(2016)·2 citations
3. 03*

   A Bottom Line for the LHC Data by Leveraging Pileup as a Zero Bias Trigger

   Benjamin Nachman🇺🇸 · Francesco Rubbo🇺🇸

   Due to a limited bandwidth and a large proton-proton interaction cross-section relative to the rate of interesting physics processes, most events produced at the Large Hadron Collider (LHC) are discarded in real time. A sophisticated trigger system must quickly decide which events should be kept and is very efficient for a broad range of processes. However, there are many processes that cannot be accommodated by this trigger system. Furthermore, there may be models of physics beyond the Standard Model (BSM) constructed after data taking that could have been triggered, but no trigger was implemented at run time. Both of these cases can be covered by exploiting pileup interactions as an effective zero bias sample. At the end of High-Luminosity LHC operations, this zero bias dataset will have accumulated about 1/fb of data from which a bottom line cross-section limit of O(1) fb can be set for BSM models already in the literature and those yet to come.

   hep-phhep-exPRD(2018)·6 citations
4. 04*

   AMS-02 Positron Excess and Indirect Detection of Three-body Decaying Dark Matter

   Hsin-Chia Cheng🇺🇸 · Wei-Chih Huang🇩🇪 · Xiaoyuan Huang🇩🇪 · Ian Low🇺🇸 · Yue-Lin Sming Tsai🇯🇵 · Qiang Yuan🇨🇳

   We consider indirect detection of meta-stable dark matter particles decaying into a stable neutral particle and a pair of standard model fermions. Due to the softer energy spectra from the three-body decay, such models could potentially explain the AMS-02 positron excess without being constrained by the Fermi-LAT gamma-ray data and the cosmic ray anti-proton measurements. We scrutinize over different final state fermions, paying special attention to handling of the cosmic ray background and including various contributions from cosmic ray propagation with the help of the \textsc{LikeDM} package. It is found that primary decays into an electron-positron pair and a stable neutral particle could give rise to the AMS-02 positron excess and, at the same time, stay unscathed against the gamma-ray and anti-proton constraints. Decays to a muon pair or a mixed flavor electron-muon pair may also be viable depending on the propagation models. Decays to all other standard model fermions are severely disfavored.

   hep-phastro-ph.HEJCAP(2017)·32 citations
5. 05*

   Conjugate boundary condition, hidden particles, and gauge-Higgs inflation

   Yugo Abe🇯🇵 · Yuhei Goto🇯🇵 · Yoshiharu Kawamura🇯🇵 · Yasunari Nishikawa

   We propose an idea that hidden particles can be separated according to gauge quantum numbers from the visible ones by the difference of boundary conditions on extra dimensions. We formulate 5-dimensional gauge theories yielding conjugate boundary conditions besides ordinary ones on $S^1/Z_2$, and examine physical implications concerning hidden particles on an extension of the standard model coexisting different types of boundary conditions. A model with conjugate boundary conditions is applied on a gauge-Higgs inflation scenario.

   hep-phastro-ph.COhep-thMod.Phys.Lett.A(2016)·4 citations
6. 06*

   $K^0\Lambda$ and $D^{-}{\Lambda }_c^{+}$ production induced by pion beams off the nucleon

   Sang-Ho Kim🇰🇷 · Hyun-Chul Kim🇰🇷 · Atsushi Hosaka🇯🇵

   We present a comparative study of the pion induced production of $K^0\Lambda$ and $D^{-}{\Lambda }_c^{+}$ off the nucleon. A hybrid framework is utilized by combining an effective Lagrangian method with a Regge approach. We consider the $t$-channel process in a plannar diagram by vector-meson Reggeon exchanges and the $u$-channel one in a non-planar diagram by baryon Reggeon exchanges. The present model reproduces the $K^0\Lambda$ production data well with a few parameters. Having fixed them, we predict the $D^{-}{\Lambda }_c^{+}$ production, which turns out to be about $10^4-10^6$ times smaller than the strangeness one, depending on the kinematical regions.

   hep-phhep-exPRD(2016)·9 citations
7. 07*

   Status and developments of event generators

   Torbjörn Sjöstrand🇸🇪

   Event generators play a crucial role in the exploration of LHC physics. This presentation summarizes news and plans for the three general-purpose pp generators HERWIG, PYTHIA and SHERPA, as well as briefer notes on a few other generators. Common themes, such as the matching and merging between matrix elements and parton showers, are highlighted. Other topics include a historical introduction, from the Lund perspective, and comments on the role of MCnet.

   hep-phPoS(2016)·36 citations
8. 08*

   Kondo cloud of single heavy quark in cold and dense matter

   Shigehiro Yasui🇯🇵

   The Kondo effect is a universal phenomena observed in a variety of fermion systems containing a heavy impurity particle whose interaction is governed by the non-Abelian interaction. At extremely high density, I study the Kondo effect by color exchange in quark matter containing a single heavy (charm or bottom) quark as an impurity particle. To obtain the ground state with the Kondo effect, I introduce the condensate mixing the light quark and the heavy quark (Kondo cloud) in the mean-field approximation. I estimate the energy gain by formation of the Kondo cloud, and present that the Kondo cloud exhibits the resonant structure. I also evaluate the scattering cross section for the light quark and the heavy quark, and discuss its effect to the finite size quark matter.

   hep-phcond-mat.str-elPLB(2017)·22 citations
9. 09*

   Natural Supersymmetry from Extra Dimensions

   Antonio Delgado🇺🇸 · Mateo Garcia-Pepin🇪🇸 · Germano Nardini🇨🇭 · Mariano Quiros🇪🇸

   We show that natural supersymmetry can be embedded in a five-dimensional theory with supersymmetry breaking à la Scherk-Schwarz (SS). There is no 'gluino-sucks' problem for stops localized in the four-dimensional brane and gluinos propagating in the full five-dimensional bulk, and sub-TeV stops are easily accommodated. The $\mu /B_{\mu }$ problem is absent as well; the SS breaking generates a Higgsino Dirac mass and no bilinear Higgs mass parameter in the superpotential is required. Moreover, for non-maximal SS twists leading to $\tan \beta \simeq 1$, the Higgs spectrum is naturally split, in agreement with LHC data. The 125-GeV Higgs mass and radiative electroweak symmetry breaking can be accommodated by minimally extending the Higgs sector with $Y=0$ $SU(2{)}_L$ triplets.

   hep-phhep-thPRD(2016)·12 citations
10. 10*

    Fundamental properties of resonances

    S. Ceci🇭🇷 · M. Hadžimehmedović🇧🇦 · H. Osmanović🇧🇦 · A. Percan🇭🇷 · B. Zauner🇭🇷

    All resonances, from hydrogen nuclei excited by the high-energy gamma rays in deep space to newly discovered particles produced in Large Hadron Collider, should be described by the same fundamental physical quantities. However, two distinct sets of properties are used to describe resonances: the pole parameters (complex pole position and residue) and the Breit-Wigner parameters (mass, width, and branching fractions). There is an ongoing decades-old debate on which of them should be abandoned. In this study of nucleon resonances emerging in the elastic pion-nucleon scattering we discover an intricate interplay of the parameters from both sets, and realize that neither set is completely independent or fundamental on its own.

    hep-phSci.Rep.(2017)·14 citations
11. 11*

    Hadronic Lorentz Violation in Chiral Perturbation Theory

    Rasha Kamand🇺🇸 · Brett Altschul🇺🇸 · Matthias R. Schindler🇺🇸

    Any possible Lorentz violation in the hadron sector must be tied to Lorentz violation at the underlying quark level. The relationships between the theories at these two levels are studied using chiral perturbation theory. Starting from a two-flavor quark theory that includes dimension-four Lorentz-violation operators, the effective Lagrangians are derived for both pions and nucleons, with novel terms appearing in both sectors. Since the Lorentz violation coefficients for nucleons and pions are all related to a single set of underlying quark coefficients, it is possible to place approximate bounds on pion Lorentz violation using only proton and neutron observations. The resulting bounds on four pion parameters are at the $10^{-23}$ level, representing improvements of ten orders of magnitude.

    hep-phhep-thnucl-thPRD(2017)·28 citations
12. 12*

    Fierz relations for Volkov spinors and the simplification of Furry picture traces

    A. Hartin🇩🇪

    Transition probability calculations of strong field particle processes in the Furry picture, typically use fermion Volkov solutions. These solutions have a relatively complicated spinor due to the interaction of the electron spin with a strong external field, which in turn leads to unwieldy trace calculations. The simplification of these calculations would aid theoretical studies of strong field phenomena such as the predicted resonance behaviour of higher order Furry picture processes. Here, Fierz transformations of Volkov spinors are developed and applied to a 1st order and a 2nd order Furry picture process. Combined with symmetry properties, the techniques presented here are generally applicable and lead to considerable simplification of Furry picture analytic calculations.

    hep-phhep-thPRD(2016)·8 citations
13. 13*

    Bridge between Hadrodynamics & HEP: Regional CP Violation in Beauty & Charm Decays

    I.I. Bigi🇺🇸

    There is a long way from `accuracy' to `precision' about {\bf CP} asymmetries in the decays of beauty \& charm hadrons. (a) We have to apply consistent parametrization of the CKM matrix. (b) Probing many-body final states (FS) is {\em not} a back-up for understanding the underlying forces; to be realistic we can hardly go beyond four-body FS. (c) Broken U-spin symmetry is a good tools to describe spectroscopy of hadrons.However the landscape is very different for weak transitions; the connection of U- \& V-spin symmetries are important. We have to understand the differences between Penguin {\em operators} vs. Penguin {\em diagrams}. (d) Collaborations of experimenters \& theorists are crucial with {\em judgment}. There is a `hot' news from the conference ICHEP2016: LHCb data show evidence of {\bf CP} asymmetries in the {\bf T}-odd moment from ${\Lambda }_b^0\to p{\pi }^{-}{\pi }^{+}{\pi }^{-}$. LHCb will follow this `road' with ${\Lambda }_b^0\to p{\pi }^{-}{K}^{+}{K}^{-}$, ${\Lambda }_b^0\to p{K}^{-}{\pi }^{+}{\pi }^{-}$ \& ${\Lambda }_b^0\to p{K}^{-}{K}^{+}{K}^{-}$ in run-1. With much more data it is crucial to probe its features in {\em regional} asymmetries. \\ A quote from Marinus, who was a $\sim$ 468 AD student of Proklos, a well-known Neoplatonic philosopher: "Only {\em being} good is one thing -- but good {\em doing} it is the other one!"

    hep-phPoS(2016)·2 citations
14. 14*

    Heavy Exotic Molecules with Charm and Bottom

    Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸

    We revisit the formation of pion-mediated heavy-light exotic molecules with both charm and bottom and their chiral partners under the general strictures of both heavy-quark and chiral symmetry. The chiral exotic partners with good parity formed using the $(0^{+},1^{+})$ multiplet are about twice more bound than their primary exotic partners formed using the $(0^{-},1^{-})$ multiplet. The chiral couplings across the multiplets $(0^{\pm },1^{\pm })$ cause the chiral exotic partners to unbind, and the primary exotic molecules to be about twice more bound, for $J\le 1$. Our multi-channel coupling results show that only the charm isosinglet exotic molecules with $J^{PC}=1^{++}$ binds, which we identify as the reported neutral $X(3872)$. Also, the bottom isotriplet exotic with $J^{PC}=1^{+-}$ binds, which we identify as a mixture of the reported charged exotics $Z_b^{+}(10610)$ and $Z_b^{+}(10650)$. The bound isosinglet with $J^{PC}=1^{++}$ is suggested as a possible neutral $X_b(10532)$ not yet reported.

    hep-phhep-exnucl-thPLB(2016)·25 citations
15. 15*

    Elastic scattering of vortex electrons provides direct access to the Coulomb phase

    I. P. Ivanov🇵🇹 · D. Seipt🇩🇪 · A. Surzhykov🇩🇪 · S. Fritzsche🇩🇪

    Vortex electron beams are freely propagating electron waves carrying adjustable orbital angular momentum with respect to the propagation direction. Such beams were experimentally realized just a few years ago and are now used to probe various electromagnetic processes. So far, these experiments used the single vortex electron beams, either propagating in external fields or impacting a target. Here, we investigate the elastic scattering of two such aligned vortex electron beams and demonstrate that this process allows one to experimentally measure features which are impossible to detect in the usual plane-wave scattering. The scattering amplitude of this process is well approximated by two plane-wave scattering amplitudes with different momentum transfers, which interfere and give direct experimental access to the Coulomb phase. This phase (shift) affects the scattering of all charged particles and has thus received significant theoretical attention but was never probed experimentally. We show that a properly defined azimuthal asymmetry, which has no counterpart in plane-wave scattering, allows one to directly measure the Coulomb phase as function of the scattering angle.

    hep-phquant-phPRD(2016)·47 citations
16. 16*

    Dynamical generation of hadronic resonances in effective models with derivative interactions

    Thomas Wolkanowski🇩🇪

    Light scalar mesons can be understood as dynamically generated resonances. They arise as 'companion poles' in the propagators of quark-antiquark seed states when accounting for hadronic loop contributions to the self-energies of the latter. Such a mechanism may explain the overpopulation in the scalar sector - there exist more resonances with total spin $J=0$ than can be described within a quark model. Along this line, we study an effective Lagrangian approach where the isovector state $a_0(1450)$ couples via both non-derivative and derivative interactions to pseudoscalar mesons. It is demonstrated that the propagator has two poles: a companion pole corresponding to $a_0(980)$ and a pole of the seed state $a_0(1450)$. The positions of these poles are in quantitative agreement with experimental data. Besides that, we investigate similar models for the isodoublet state $K_0^{\ast }(1430)$ by performing a fit to $\pi K$ phase shift data in the $I=1/2,$ $J=0$ channel. We show that, in order to fit the data accurately, a companion pole for the $K_0^{\ast }(800)$, that is, the light $\kappa$, is required. A large-$N_c$ study confirms that both resonances below $1$ GeV are predominantly four-quark states, while the heavy states are quarkonia.

    hep-phnucl-th2 citations
17. 17*

    Surprises with Nonrelativistic Naturalness

    Petr Horava🇺🇸

    We explore the landscape of technical naturalness for nonrelativistic systems, finding surprises which challenge and enrich our relativistic intuition already in the simplest case of a single scalar field. While the immediate applications are expected in condensed matter and perhaps in cosmology, the study is motivated by the leading puzzles of fundamental physics involving gravity: The cosmological constant problem and the Higgs mass hierarchy problem.

    ↳ hep-thastro-ph.COcond-mat.supr-congr-qc+1Int.J.Mod.Phys.D(2016)·11 citations
18. 18*

    The $\sigma$ exchange effect in the Lamb shift of muonic hydrogen by two photons and two pions exchange

    Hai-Qing Zhou🇨🇳

    Based on the simple phenomenological $\sigma \pi \pi$, $\sigma NN$ and $\pi \pi \gamma$ interactions, we estimate the $\sigma$ exchange effect in the Lamb shift of muonic hydrogen. We at first calculate the effective couplings of $\sigma \mu \mu$ by two photons and two pions exchange, then calculate the corresponding corrections to the energy shift of the 2S/2P states of muonic hydrogen. We find the correction to the energy shift of 2S state is about -14$\mu$eV by the current used parameters, which is about $44\%$ of the usual two photons exchange contribution, and is larger than the current experimental precision, and should be considered in the experimental analysis.

    ↳ nucl-thhep-phnucl-ex0 citations
19. 19*

    On the gauge-invariant operator $A_{\min }^2$ in Euclidean Yang-Mills theories

    M.A.L.Capri🇧🇷 · D.Fiorentini🇧🇷 · M.S.Guimaraes🇧🇷 · B.W.Mintz🇧🇷 · L.F.Palhares🇧🇷 · S. P. Sorella🇧🇷

    We review our recent work on the gauge-invariant non-local dimension-two operator $A_{\min }^2$, whose minimization is defined along the gauge orbit. Albeit non-local, the operator $A_{\min }^2$ can be cast in local form through the introduction of an auxiliary Stueckelberg field. The whole procedure results into a local action which turns out to be renormalizable to all orders.

    ↳ hep-thhep-lathep-phNucl.Part.Phys.Proc.(2016)·1 citation
20. 20*

    Search for a narrow baryonic state decaying to $p{K}_0^S$ and $\bar{p}{K}_0^S$ in deep inelastic scattering with the HERA II data

    Ryuma Hori (for the ZEUS Collaboration)🇯🇵

    This paper presents the result of a search for a narrow strange baryonic state in the invariant-mass distribution of $p{K}_S^0(\overline{p}{K}_S^0)$ in HERA II data (2003-2007). The search was performed in the deep inelastic scattering (DIS) data with photon virtuality, $Q^2$, between 20 and 100 GeV. The analysis in HERA II period has improvements over the previous ZEUS analysis in HERA I period (1996-2000). These consist of large statistics and improved particle identification performance by using both of the CTD $dE/dx$ and the MVD $dE/dx$ in this search. Contrary to evidence for such an exotic state around 1.52 GeV in the HERA I data, no such state is found in this analysis. The upper limits on the production cross section are set at 95% confidence level.

    ↳ hep-exhep-phPoS(2016)·0 citations
21. 21*

    Hadro-quarkonium from Lattice QCD

    Maurizio Alberti🇩🇪 · Gunnar S. Bali🇩🇪 · Sara Collins🇩🇪 · Francesco Knechtli🇩🇪 · Graham Moir🇬🇧 · Wolfgang Söldner🇩🇪

    The hadro-quarkonium picture [S. Dubinskiy and M.B. Voloshin, Phys. Lett. B 666, 344 (2008)] provides one possible interpretation for the pentaquark candidates with hidden charm, recently reported by the LHCb Collaboration, as well as for some of the charmonium-like "X,Y,Z" states. In this picture, a heavy quarkonium core resides within a light hadron giving rise to four- or five-quark/antiquark bound states. We test this scenario in the heavy quark limit by investigating the modification of the potential between a static quark-antiquark pair induced by the presence of a hadron. Our lattice QCD simulations are performed on a Coordinated Lattice Simulations (CLS) ensemble with $N_f=2+1$ flavours of non-perturbatively improved Wilson quarks at a pion mass of about 223 MeV and a lattice spacing of about 0.0854 fm. We study the static potential in the presence of a variety of light mesons as well as of octet and decuplet baryons. In all these cases, the resulting configurations are favoured energetically. The associated binding energies between the quarkonium in the heavy quark limit and the light hadron are found to be smaller than a few MeV, similar in strength to deuterium binding. It needs to be seen if the small attraction survives in the infinite volume limit and supports bound states or resonances.

    ↳ hep-lathep-phPRD(2017)·62 citations
22. 22*

    Massively parallel simulations of relativistic fluid dynamics on graphics processing units with CUDA

    Dennis Bazow🇺🇸 · Ulrich W. Heinz🇺🇸 · Michael Strickland🇺🇸

    Relativistic fluid dynamics is a major component in dynamical simulations of the quark-gluon plasma created in relativistic heavy-ion collisions. Simulations of the full three-dimensional dissipative dynamics of the quark-gluon plasma with fluctuating initial conditions are computationally expensive and typically require some degree of parallelization. In this paper, we present a GPU implementation of the Kurganov-Tadmor algorithm which solves the 3+1d relativistic viscous hydrodynamics equations including the effects of both bulk and shear viscosities. We demonstrate that the resulting CUDA-based GPU code is approximately two orders of magnitude faster than the corresponding serial implementation of the Kurganov-Tadmor algorithm. We validate the code using (semi-)analytic tests such as the relativistic shock-tube and Gubser flow.

    ↳ physics.comp-phhep-phnucl-thComput.Phys.Commun.(2018)·39 citations
23. 23*

    Search for Violation of CPT and Lorentz Invariance in $B_s^0$ Meson Oscillations using the D0 Detector

    D0 Collaboration (R. Van Kooten for the collaboration)

    A search is presented for CPT-violating effects in the mixing of $B_s^0$ mesons using the D0 detector at the Fermilab Tevatron Collider. The CPT-violating asymmetry in the decay $B_s^0\to {\mu }^{\pm }{D}_s^{\mp }X$ as a function of sidereal phase is measured. No evidence for CPT-violating effects is observed and limits are placed on CPT- and Lorentz-invariance violating coupling coefficients.

    ↳ hep-exhep-ph0 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.