Mon·Aug 15, 2016Monday·August 15, 2016

1. 01*

   Revisiting fermion helicity flip in Podolsky's Electromagnetism

   Jorge Henrique Sales🇧🇷 · Alfredo Takashi Suzuki🇧🇷 · Ronaldo Thibes🇧🇷

   The spin projection of a massive particle onto its direction of motion is called helicity (or "handedness"). It can therefore be positive or negative. When a particle's helicity changes from positive to negative (or vice-versa) due to its interaction with other particles or fields, we say there is a helicity flip. In this work we show that such helicity flip can be seen for an electron of $20MeV$ of energy interacting with a charged scalar meson through the exchange of a virtual photon. This photon {\it does not} necessarily need to be Podolsky's proposed photon; in fact, it is independent of it.

   hep-ph0 citations
2. 02*

   Standard Model Extended by a Heavy Singlet: Linear vs. Nonlinear EFT

   G. Buchalla🇩🇪 · O. Cata🇩🇪 · A. Celis🇩🇪 · C. Krause🇩🇪

   We consider the Standard Model extended by a heavy scalar singlet in different regions of parameter space and construct the appropriate low-energy effective field theories up to first nontrivial order. This top-down exercise in effective field theory is meant primarily to illustrate with a simple example the systematics of the linear and nonlinear electroweak effective Lagrangians and to clarify the relation between them. We discuss power-counting aspects and the transition between both effective theories on the basis of the model, confirming in all cases the rules and procedures derived in previous works from a bottom-up approach.

   hep-phNPB(2017)·68 citations
3. 03*

   Powheg-Pythia matching scheme effects in NLO simulation of dijet events

   Andy Buckley🇬🇧 · Debottam Bakshi Gupta🇺🇸

   One of the most important developments in Monte Carlo simulation of collider events for the LHC has been the arrival of schemes and codes for matching of parton showers to matrix elements calculated at next-to-leading order in the QCD coupling. The POWHEG scheme, and particularly its implementation in the POWHEG-BOX code, has attracted most attention due to ease of use and effective portability between parton shower algorithms. But formal accuracy to NLO does not guarantee predictivity, and the beyond-fixed-order corrections associated with the shower may be large. Further, there are open questions over which is the "best" variant of the POWHEG matching procedure to use, and how to evaluate systematic uncertainties due to the degrees of freedom in the scheme. In this paper we empirically explore the scheme variations allowed in Pythia8 matching to POWHEG-BOX dijet events, demonstrating the effects of both discrete and continuous freedoms in emission vetoing details for both tuning to data and for estimation of systematic uncertainties from the matching and parton shower aspects of the POWHEG-BOX+Pythia8 generator combination.

   hep-ph17 citations
4. 04*

   Particle Physics Models for the 17 MeV Anomaly in Beryllium Nuclear Decays

   Jonathan L. Feng🇺🇸 · Bartosz Fornal🇺🇸 · Iftah Galon🇺🇸 · Susan Gardner🇺🇸 · Jordan Smolinsky🇺🇸 · Tim M. P. Tait🇺🇸 · Philip Tanedo🇺🇸

   The 6.8$\sigma$ anomaly in excited 8Be nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in 8Be decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited 8Be decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the 8Be anomaly. In the first model, the new force carrier is a U(1)B gauge boson that kinetically mixes with the photon; in the second model, it is a U(1)(B-L) gauge boson with a similar kinetic mixing. In both cases, the models predict relatively large charged lepton couplings ~ 0.001 that can resolve the discrepancy in the muon anomalous magnetic moment and are amenable to many experimental probes. The models also contain vectorlike leptons at the weak scale that may be accessible to near future LHC searches.

   hep-phhep-exnucl-exnucl-thPRD(2017)·257 citations
5. 05*

   Probing the MSSM explanation of the muon g-2 anomaly in dark matter experiments and at a 100 TeV $pp$ collider

   Archil Kobakhidze🇦🇺 · Matthew Talia🇦🇺 · Lei Wu🇦🇺

   We explore the ability of current and future dark matter and collider experiments in probing anomalous magnetic moment of the muon, $(g-2{)}_{\mu }$, within the Minimal Supersymmetric Standard Model (MSSM). We find that the latest PandaX-II/LUX-2016 data gives a strong constraint on parameter space that accommodates the $(g-2{)}_{\mu }$ within $2\sigma$ range, which will be further excluded by the upcoming XENON-1T (2017) experiment. We also find that a 100 TeV $pp$ collider can cover most of our surviving samples that satisfy DM relic density within $3\sigma$ range through $Z$ or $h$ resonant effect by searching for trilepton events from ${\tilde{\chi }}_2^0{\tilde{\chi }}_1^{+}$ associated production. While the samples that are beyond future sensitivity of trilepton search at a 100 TeV $pp$ collider and the DM direct detections are either higgsino/wino-like LSPs or bino-like LSPs co-annihilating with sleptons. Such compressed regions may be covered by the monojet(-like) searches at a 100 TeV $pp$ collider.

   hep-phhep-exPRD(2017)·39 citations
6. 06*

   $D\to a_1,f_1$ transition form factors and semileptonic decays via 3-point QCD sum rules

   Yabing Zuo🇨🇳 · Yue Hu🇨🇳 · Linlin He🇨🇳 · Wei Yang🇨🇳 · Yan Chen🇨🇳 · Yannan Hao🇨🇳

   By using the 3-point QCD sum rules, we calculate the transition form factors of $D$ decays into the spin triplet axial vector mesons $a_1(1260)$, $f_1(1285)$, $f_1(1420)$. In the calculations, we consider the quark contents of each meson in detail. In view of the fact that the isospin of $a_1(1260)$ is one, we calculate the $D^{+}\to a_1^0(1260)$ and $D^0\to a_1^{-}(1260)$ transition form factors separately. In the case of $f_1(1285),f_1(1420)$, the mixing between light flavor $SU(3)$ singlet and octet is taken into account. Based on the form factors obtained here, we give predictions for the branching ratios of relevant semileptonic decays, which can be tested in the future experiments.

   hep-phInt.J.Mod.Phys.A(2016)·12 citations
7. 07*

   Analysis of ${\Lambda }_b\to$ $\Lambda {\mu }^{+}{\mu }^{-}$ decay in scalar leptoquark model

   Shuai-wei Wang🇨🇳 · Ya-dong Yang🇨🇳

   We analyze the baryonic semilepton decay ${\Lambda }_b\to$ $\Lambda {\mu }^{+}{\mu }^{-}$ in the scalar leptoquark models with $X(3,2,7/6)$ and $X(3,2,1/6)$ states, respectively. We also discuss the effects of this two NP models on some physical observables. For some measured observables, like the differential decay width, the longitudinal polarization of the dilepton system, the lepton-side forward-backward asymmetry and the baryon-side forward-backward asymmetry, we find, the prediction values of SM are consistent with the current data in the most $q^2$ ranges, where the prediction values of this two NP models can also keep consistent with the current data with $1\sigma$. However, in some $q^2$ ranges, the prediction values of SM are difficult to meet the current data, but the contributions of this two NP models can meet them or keep closer to them. For the double lepton polarization asymmetries, $P_{LT}$, $P_{TL}$, $P_{NN}$ and $P_{TT}$ are sensitive to the scalar leptoquark model $X(3,2,7/6)$ but not to $X(3,2,1/6)$. However, $P_{LN}$, $P_{NL}$, $P_{TN}$ and $P_{NT}$ are not sensitive to this two NP models.

   hep-phAdv.High Energy Phys.(2016)·12 citations
8. 08*

   Dark Side of the Standard Model: Dormant New Physics Awaken

   Shinya Matsuzaki🇯🇵 · Hiroshi Ohki🇺🇸 · Koichi Yamawaki🇯🇵

   We find that the nonperturbative physics of the standard-model Higgs Lagrangian provides a dark matter candidate, "dormant skyrmion in the standard model", the same type of the skyrmion, a soliton, as in the hadron physics. It is stabilized by another nonperturbative object in the standard model, the dynamical gauge boson of the hidden local symmetry, which is also an analogue of the rho meson.

   hep-phastro-ph.COhep-exhep-th6 citations
9. 09*

   Near and Far from Equilibrium Power-Law Statistics

   Tamas S Biro🇭🇺 · Gergely G Barnafoldi🇭🇺 · Gabor Biro🇭🇺 · Ke Ming Shen🇨🇳

   We analyze the connection between $p_T$ and multiplicity distributions in a statistical framework. We connect the Tsallis parameters, $T$ and $q$, to physical properties like average energy per particle and the second scaled factorial moment, $F_2=⟨n(n-1)⟩/{⟨n⟩}^2$, measured in multiplicity distributions. Near and far from equilibrium scenarios with master equations for the probability of having $n$ particles, $P_n$, are reviewed based on hadronization transition rates, ${\mu }_n$, from $n$ to $n+1$ particles.

   hep-phJ.Phys.Conf.Ser.(2017)·8 citations
10. 10*

    Generation of central exclusive final states

    Leif Lönnblad🇸🇪 · Radek Žlebčík🇨🇿

    We present a scheme for the generation of central exclusive final states in the Pythia 8 program. The implementation allows for the investigation of higher order corrections to such exclusive processes as approximated by the initial-state parton shower in Pythia 8. To achieve this, the spin and colour decomposition of the initial-state shower has been worked out, in order to determine the probability that a partonic state generated from an inclusive sub-process followed by a series of initial-state parton splittings can be considered as an approximation of an exclusive colour- and spin-singlet process. We use our implementation to investigate effects of parton showers on some examples of central exclusive processes, and find sizeable effects on di-jet production, while the effects on e.g. central exclusive Higgs production are minor.

    hep-phEPJC(2016)·6 citations
11. 11*

    Dimesonic states with the heavy-light flavour mesons

    D. P. Rathaud🇮🇳 · Ajay Kumar Rai🇮🇳

    In this work, we have calculated the mass spectra and decay properties of dimesonic states in the variational scheme. The inter-mesonic interaction considered as the Hellmann potential and One Pion Exchange potential. The mass spectra of the $D\overline{D^{\ast }}$, $D^{\ast }\overline{D^{\ast }}$, $D\overline{B^{\ast }}$, $B^{\ast }\overline{D}$, $B\overline{B^{\ast }}$, $B^{\ast }\overline{B^{\ast }}$ bound states are calculated. The states X(3872), $X_{2c}(4013)$, $Z_b(10610)/X_b$ and $Z_b(10650)/X_{b2}$ are compared with $D\overline{D^{\ast }}$, $D^{\ast }\overline{D^{\ast }}$, $B\overline{B^{\ast }}$ and $B^{\ast }\overline{B^{\ast }}$ dimesonic bound states. {\bf To probe the molecular structure of the compared states, we have calculated the decay properties sensitive to their long and short distance structure of the hadronic molecule. The radiative decay for the state X(3872) into $J/\psi \gamma$ and $\psi (2S)\gamma$ have been calculated and the ratio is found to be ten times lesser than the experimental value whereas the other decay modes are comparable with other theoretical and experimental results. This results restrict us to assigned the pure molecular structure to the X(3872). But, Our results suggests that the compared states are close to the molecular structure or have dominant molecular component in their wave function. Apart from these, the other calculated mass spectra of dimesonic states are predicted and for such bound states, the experimental search are suggested.}

    hep-phEur.Phys.J.Plus(2017)·32 citations
12. 12*

    Theory of electric dipole moments and lepton flavour violation

    Martin Jung🇩🇪

    Electric dipole moments and charged-lepton flavour-violating processes are extremely sensitive probes for new physics, complementary to direct searches as well as flavour-changing processes in the quark sector. Beyond the "smoking-gun" feature of a potential significant measurement, however, it is crucial to understand their implications for new physics models quantitatively. The corresponding multi-scale problem of relating the existing high-precision measurements to fundamental parameters can be approached model-independently to a large extent; however, care must be taken to include the uncertainties from especially nuclear and QCD calculations properly.

    hep-phPoS(2016)·0 citations
13. 13*

    BFKL pomeron with massive gluons and running coupling

    Eugene Levin🇨🇱 · Lev Lipatov🇷🇺 · Marat Siddikov🇨🇱

    In this paper we proceed with the study of the Pomeron spectrum, by solving numerically the BFKL equation with massive gluons and running coupling. The spectrum of Regge singularities is discrete and the leading Pomeron has a considerable dependence on nonperturbative effects, for which we use Higgs mechanism as a model. We cross-checked this result with variational method and confirmed the infrared sensitivity of leading Pomeron. This fact is related to the infrared instability of the BFKL equation in QCD, with a running coupling. The subleading poles have a mild sensitivity to the soft physics, and are well described by known semiclassical methods. We also discuss the dependence on various prescriptions of the running coupling arguments.

    hep-phhep-thPRD(2016)·7 citations
14. 14*

    Exclusive J/psi and Upsilon photoproduction and the low x gluon

    S. P. Jones🇩🇪 · A. D. Martin🇬🇧 · M. G. Ryskin🇬🇧 · T. Teubner🇬🇧

    We discuss the potential to constrain the small-$x$ PDFs using the exclusive production of heavy vector mesons. The calculation of $J/\psi$ and ${\rm Y}$ photoproduction at NLO in collinear factorisation is described. The different behaviour of the NLO corrections for $J/\psi$ and ${\rm Y}$ is highlighted and we outline what might be expected from the inclusion of these processes in a PDF fit.

    hep-phPoS(2016)·1 citation
15. 15*

    Automation of 2-loop Amplitude Calculations

    S. P. Jones🇩🇪

    Some of the tools and techniques that have recently been used to compute Higgs boson pair production at NLO in QCD are discussed. The calculation relies on the use of integral reduction, to reduce the number of integrals which must be computed, and expressing the amplitude in terms of a quasi-finite basis, which simplifies their numeric evaluation. Emphasis is placed on sector decomposition and Quasi-Monte Carlo (QMC) integration which are used to numerically compute the master integrals.

    hep-phPoS(2016)·19 citations
16. 16*

    Next-to-Leading Order Corrections to Higgs Boson Pair Production in Gluon Fusion

    Matthias Kerner🇩🇪

    We present a calculation of the next-to-leading order QCD corrections to the production of Higgs boson pairs in gluon fusion keeping the full dependence on the mass of the top quark. The virtual corrections, involving two-loop integrals with up to four mass scales, have been calculated numerically and we present an efficient algorithm to obtain accurate results of the virtual amplitude using numerical integrations. Taking the top quark mass into account we obtain significant differences compared to results obtained in the heavy top limit.

    hep-phPoS(2016)·11 citations
17. 17*

    In-Medium Pion Valence Distributions in a Light-Front Model

    J. P. B. C de Melo · K. Tsushima · (Laboratório de Fisica Teorica e Computacional - LFTC, Universidade Cruzeiro do Sul) · I. Ahmed · (National Center for Physics, Quaidi-i-Azam University Campus)

    Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

    hep-phhep-exhep-latnucl-ex+1PLB(2017)·12 citations
18. 18*

    Searches for Anisotropic Lorentz-Invariance Violation in the Photon Sector

    Fabian Kislat🇺🇸 · Henric Krawczynski🇺🇸

    Lorentz invariance, the fundamental symmetry of Einstein's theory of Special Relativity, has been established and tested by many classical and modern experiments. However, many theories that unify the Standard Model of particle physics and General Relativity predict a violation of Lorentz invariance at the Planck scale. While this energy range cannot be reached by current experiments, minute deviations from Lorentz symmetry may be present at lower energies. Astrophysical experiments are very suitable to search for these deviations, since their effects accumulate as photons travel across large distances. In this paper, we describe astrophysical methods that we used to constrain the photon dispersion and vacuum birefringence.

    ↳ astro-ph.HEhep-ph0 citations
19. 19*

    General sGoldstino Inflation

    Sergio Ferrara🇨🇭 · Diederik Roest🇳🇱

    We prove that all inflationary models, including those with dark energy after the end of inflation, can be embedded in minimal supergravity with a single chiral superfield. Moreover, the amount of supersymmetry breaking is independently tunable due to a degeneracy in the choice for the superpotential. The inflaton is a scalar partner of the Goldstino in this set-up. We illustrate our general procedure with two examples that are favoured by the Planck data.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2016)·27 citations
20. 20*

    Conserved charge fluctuations are not conserved during the hadronic phase

    J. Steinheimer🇩🇪 · V. Vovchenko🇩🇪 · J. Aichelin🇫🇷 · M. Bleicher🇩🇪 · H. Stöcker🇩🇪

    We study the correlation between the distributions of the net-charge, net-kaon, net-baryon and net-proton number at hadronization and after the final hadronic decoupling by simulating ultra relativistic heavy ion collisions with the hybrid version of the ultrarelativistic quantum molecular dynamics (UrQMD) model. We find that due to the hadronic rescattering these distributions are not strongly correlated. The calculated change of the correlation, during the hadronic expansion stage, does not support the recent paradigm, namely that the measured final moments of the experimentally observed distributions do give directly the values of those distributions at earlier times, when the system had been closer to the QCD crossover.

    ↳ nucl-thhep-phPLB(2018)·31 citations
21. 21*

    A new direction for dark matter research: intermediate mass compact halo objects

    G. Chapline🇺🇸 · P.H. Frampton🇬🇧

    The failure to find evidence for elementary particles that could serve as the constituents of dark matter brings to mind suggestions that dark matter might consist of massive compact objects (MACHOs). In particular, it has recently been argued that MACHOs with masses > 15 solar masses may have been prolifically produced at the onset of the big bang. Although a variety of astrophysical signatures for primordial MACHOs with masses in this range have been discussed in the literature, we favor a strategy that uses the potential for gravitational microlensing of stars outside our galaxy to directly detect the presence of MACHOs in the halo of our galaxy. We point out that the effect of the motion of the Earth on the shape of the microlensing brightening curves provides a promising approach to confirming over the course of next several years that dark matter consists of MACHOs.

    ↳ gr-qcastro-ph.GAhep-phJCAP(2016)·40 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.