HEP Phenomenology·hep-ph

Mon·Nov 27, 2017Monday·November 27, 2017

17 papers—9 primary·8 cross-listed·reconstructed*

01*
Singlet-Triplet Fermionic Dark Matter and LHC Phenomenology
Sandhya Choubey🇮🇳 · Sarif Khan🇮🇳 · Manimala Mitra🇮🇳 · Subhadeep Mondal🇫🇮
It is well known that for the pure standard model triplet fermionic WIMP-type dark matter (DM), the relic density is satisfied around 2 TeV. For such a heavy mass particle, the production cross-section at 13 TeV run of LHC will be very small. Extending the model further with a singlet fermion and a triplet scalar, DM relic density can be satisfied for even much lower masses. The lower mass DM can be copiously produced at LHC and hence the model can be tested at collider. For the present model we have studied the multi jet ( $\geq 2 j$ ) + missing energy ( $E_{T}$ ) signal and show that this can be detected in the near future of the LHC 13 TeV run. We also predict that the present model is testable by the earth based DM direct detection experiments like Xenon-1T and in future by Darwin.
hep-phEPJC(2018)·29 citations
02*
NLO QCD and EW corrections to processes involving off-shell top quarks
Ansgar Denner🇩🇪 · Jean-Nicolas Lang🇩🇪 · Mathieu Pellen🇩🇪 · Sandro Uccirati🇮🇹
We review recent results on next-to-leading order (NLO) QCD and electroweak (EW) corrections for processes involving off-shell top quarks. For the off-shell production of two top quarks that decay leptonically, the full NLO EW corrections have been computed. For the very same process in association with a Higgs boson, EW corrections have been calculated and combined with existing NLO QCD corrections. In both cases, selected differential distributions are shown. In these proceedings, particular emphasis is put on the effect of the EW corrections as well as the off-shell contributions.
hep-phhep-exPoS(2017)·1 citation
03*
$B$ -meson anomalies and Higgs physics in flavored $U (1)^{'}$ model
Ligong Bian🇨🇳 · Hyun Min Lee🇰🇷 · Chan Beom Park🇰🇷
We consider a simple extension of the Standard Model with flavor-dependent $U (1)^{'}$ , that has been proposed to explain some of $B$ -meson anomalies recently reported at LHCb. The $U (1)^{'}$ charge is chosen as a linear combination of anomaly-free $B_{3} - L_{3}$ and $L_{μ} - L_{τ}$ . In this model, the flavor structure in the SM is restricted due to flavor-dependent $U (1)^{'}$ charges, in particular, quark mixings are induced by a small vacuum expectation value of the extra Higgs doublet. As a result, it is natural to get sizable flavor-violating Yukawa couplings of heavy Higgs bosons involving the bottom quark. In this article, we focus on the phenomenology of the Higgs sector of the model including extra Higgs doublet and singlet scalars. We impose various bounds on the extended Higgs sector from Higgs and electroweak precision data, $B$ -meson mixings and decays as well as unitarity and stability bounds, then discuss the productions and decays of heavy Higgs bosons at the LHC.
hep-phEPJC(2018)·62 citations
04*
$S$ -wave $K π$ contributions to the hadronic charmonium $B$ decays in the perturbative QCD approach
Zhou Rui🇨🇳 · Wen-Fei Wang🇨🇳
We extend our recent works on the two-pion $S$ -wave resonance contributions to the kaon-pion ones in the $B$ meson hadronic charmonium decay modes based on the perturbative QCD approach. The $S$ -wave $K π$ time-like form factor in its distribution amplitudes is described by the LASS parametrization, which consists of the $K_{0}^{*} (1430)$ resonant state together with an effective range nonresonant component. The predictions for the decays $B \to J / ψ K π$ in this work agree well with the experimental results from $B A B A R$ and Belle Collaborations. We also discuss theoretical uncertainties, indicating the results of this work, which can be tested by the LHCb and Belle-II experiments, are reasonably accurate.
hep-phPRD(2018)·33 citations
05*
Improved analysis for $μ^{-} e^{-} \to e^{-} e^{-}$ in muonic atoms by photonic interaction
Yuichi Uesaka🇯🇵 · Yoshitaka Kuno🇯🇵 · Joe Sato🇯🇵 · Toru Sato🇯🇵 · Masato Yamanaka🇯🇵
Studies of the charged lepton flavor violating process of $μ^{-} e^{-} \to e^{-} e^{-}$ in muonic atoms by the four Fermi interaction [Y. Uesaka \textit{et al}., Phys. Rev. D {\bf 93}, 076006 (2016)] are extended to include the photonic interaction. The wave functions of a muon and electrons are obtained by solving the Dirac equation with the Coulomb interaction of a finite nuclear charge distribution. We find suppression of the $μ^{-} e^{-} \to e^{-} e^{-}$ rate over the initial estimation for the photonic interaction, in contrast to enhancement for the four Fermi interaction. It is due to the Coulomb interaction of scattering states and relativistic lepton wave functions. This finding suggests that the atomic number dependence of the $μ^{-} e^{-} \to e^{-} e^{-}$ rate could be used to distinguish between the photonic and the four Fermi interactions.
hep-phhep-exPRD(2018)·19 citations
06*
Adiabatic out-of-equilibrium solutions to the Boltzmann equation in warm inflation
Mar Bastero-Gil🇪🇸 · Arjun Berera🇬🇧 · Rudnei O. Ramos🇧🇷 · Joao G. Rosa🇵🇹
We show that, in warm inflation, the nearly constant Hubble rate and temperature lead to an adiabatic evolution of the number density of particles interacting with the thermal bath, even if thermal equilibrium cannot be maintained. In this case, the number density is suppressed compared to the equilibrium value but the associated phase-space distribution retains approximately an equilibrium form, with a smaller amplitude and a slightly smaller effective temperature. As an application, we explicitly construct a baryogenesis mechanism during warm inflation based on the out-of-equilibrium decay of particles in such an adiabatically evolving state. We show that this generically leads to small baryon isocurvature perturbations, within the bounds set by the Planck satellite. These are correlated with the main adiabatic curvature perturbations but exhibit a distinct spectral index, which may constitute a smoking gun for baryogenesis during warm inflation. Finally, we discuss the prospects for other applications of adiabatically evolving out-of-equilibrium states.
hep-phastro-ph.COgr-qchep-thJHEP(2018)·27 citations
07*
Electrons in an eccentric background field
Martin Lavelle🇬🇧 · David McMullan🇬🇧
We present a description of electrons propagating in an elliptically polarised plane wave background which includes circular and linear polarisations as special cases. We calculate to all orders in the background field the two point function and relate it to various expressions found in the literature. The background field induced mass shift of the electron is shown to be polarisation independent in the full elliptic class. The matrix nature of this mass shift in the fermionic theory is discussed. The extent to which a momentum space description is possible for this system is clarified.
hep-phhep-thPRD(2018)·8 citations
08*
Quarkonium decay into photon plus graviton: a golden channel to discriminate General Relativity from Massive Gravity?
Dong Bai🇨🇳 · Wen Chen🇨🇳 · Yu Jia🇨🇳
After the recent historical discovery of gravitational wave, it is curious to speculate upon the detection prospect of the quantum graviton in the terrestrial accelerator-based experiment. We carefully investigate the "golden" channels, $J / ψ (Υ) \to γ + graviton$ , which can be pursued at \textsf{BESIII} and \textsf{Belle 2} experiments, by searching for single-photon plus missing energy events. Within the effective field theory (EFT) framework of General Relativity (GR) together with Nonrelativistic QCD (NRQCD), we are capable of making solid predictions for the corresponding decay rates. It is found that these extremely suppressed decays are completely swamped by the Standard Model background events $J / ψ (Υ) \to γ + ν ν ˉ$ . Meanwhile, we also study these rare decay processes in the context of massive gravity, and find the respective decay rates in the limit of vanishing graviton mass drastically differ from their counterparts in GR. Counterintuitive as the failure of smoothly recovering GR results may look, our finding is reminiscent of the van Dam-Veltman-Zakharov (vDVZ) discontinuity widely known in classical gravity, which can be traced to the finite contribution of the helicity-zero graviton in the massless limit. Nevertheless, at this stage we are not certain about the fate of the discontinuity encountered in this work, whether it is merely a pathology or not. If it could be endowed with some physical significance, the future observation of these rare decay channels, would, in principle, shed important light on the nature of gravitation, whether the graviton is strictly massless, or bears a very small but nonzero mass.
hep-phgr-qchep-ex1 citation
09*
Do astrophysical data disfavour the minimal supersymmetric standard model?
Arpan Kar🇮🇳 · Sourav Mitra🇮🇳 · Biswarup Mukhopadhyaya🇮🇳 · Tirthankar Roy Choudhury🇮🇳
If the minimal supersymmetric standard model (MSSM) is the only new physics around the TeV-scale, it has to account for the entire dark matter relic density, or else it will cease to be `minimal'. We use this expectation to obtain the best quantitative explanation of the galactic centre $γ$ -ray excess. The $γ$ -ray data/flux limits from other astrophysical sources are also taken into account, together with all laboratory constraints. The lower limit on the relic density, together with the latest direct dark matter search constraints and the shape of the galactic centre $γ$ -ray spectrum, makes the MSSM fits appear rather poor. A comparison with similar fits of the Higgs boson mass from indirect and direct search results makes one suspicious that the MSSM is not a good explanation of data related to dark matter.
hep-phastro-ph.HE2 citations
10*
Semilocal momentum-space regularized chiral two-nucleon potentials up to fifth order
P. Reinert🇩🇪 · H. Krebs🇩🇪 · E. Epelbaum🇩🇪
We introduce new semilocal two-nucleon potentials up to fifth order in the chiral expansion. We employ a simple regularization approach for the pion-exchange contributions which (i) maintains the long-range part of the interaction, (ii) is implemented in momentum space and (iii) can be straightforwardly applied to regularize many-body forces and current operators. We discuss in detail the two-nucleon contact interactions at fourth order and demonstrate that three terms out of fifteen used in previous calculations can be eliminated via suitably chosen unitary transformations. The removal of the redundant contact terms results in a drastic simplification of the fits to scattering data and leads to interactions which are much softer (i.e. more perturbative) than our recent semilocal coordinate-space regularized potentials. Using the pion-nucleon low-energy constants from matching pion-nucleon Roy-Steiner equations to chiral perturbation theory, we perform a comprehensive analysis of nucleon-nucleon scattering and the deuteron properties up to fifth chiral order and study the impact of the leading F-wave two-nucleon contact interactions which appear at sixth order. The resulting chiral potentials lead to an outstanding description of the proton-proton and neutron-proton scattering data from the self-consistent Granada-2013 database below the pion production threshold, which is significantly better than for any other chiral potential. For the first time, the chiral potentials match in precision and even outperform the available high-precision phenomenological potentials, while the number of adjustable parameters is, at the same time, reduced by about ~40%. Last but not least, we perform a detailed error analysis and, in particular, quantify for the first time the statistical uncertainties of the fourth- and the considered sixth-order contact interactions.
↳ nucl-thhep-phnucl-exEPJA(2018)·372 citations
11*
Tetraquark resonances computed with static lattice QCD potentials and scattering theory
Pedro Bicudo🇵🇹 · Marco Cardoso🇵🇹 · Antje Peters🇩🇪 · Martin Pflaumer🇩🇪 · Marc Wagner🇩🇪
We study tetraquark resonances with lattice QCD potentials computed for two static quarks and two dynamical quarks, the Born-Oppenheimer approximation and the emergent wave method of scattering theory. As a proof of concept we focus on systems with isospin $I = 0$ , but consider different relative angular momenta $l$ of the heavy $b$ quarks. We compute the phase shifts and search for $\mbox S$ and $\mbox T$ matrix poles in the second Riemann sheet. We predict a new tetraquark resonance for $l = 1$ , decaying into two $B$ mesons, with quantum numbers $I (J^{P}) = 0 (1^{-})$ , mass $m = 1057 6_{- 4}^{+ 4} MeV$ and decay width $Γ = 11 2_{- 103}^{+ 90} MeV$ .
↳ hep-lathep-phEPJ Web Conf.(2018)·0 citations
12*
Primordial Black Holes for the LIGO Events in the Axion-like Curvaton Model
Kenta Ando🇯🇵 · Keisuke Inomata🇯🇵 · Masahiro Kawasaki🇯🇵 · Kyohei Mukaida🇩🇪 · Tsutomu T. Yanagida🇯🇵
We revise primordial black hole (PBH) formation in the axion-like curvaton model and investigate whether PBHs formed in this model can be the origin of the gravtitational wave (GW) signals detected by the Advanced LIGO. In this model, small-scale curvature perturbations with large amplitude are generated, which is essential for PBH formation. On the other hand, large curvature perturbations also become a source of primordial GWs by their second-order effects. Severe constraints are imposed on such GWs by pulsar timing array (PTA) experiments. We also check the consistency of the model with these constraints. In this analysis, it is important to take into account the effect of non-Gaussianity, which is generated easily in the curvaton model. We see that, if there are non-Gaussianities, the fixed amount of PBHs can be produced with a smaller amplitude of the primordial power spectrum.
↳ astro-ph.COhep-phPRD(2018)·139 citations
13*
Searches for very weakly-coupled particles beyond the Standard Model with NA62
Babette Döbrich (for the NA62 collaboration)🇨🇭
The NA62 experiment at CERN is designed to measure precisely the rare decay $K^{+} \to π^{+} ν ν ˉ$ . The intensity and energy of the SPS proton beam used to produce the $K^{+}$ , as well as the hermetic detector coverage and overall geometry, give in addition the opportunity to search for hypothesized weakly-coupled particles at the MeV-GeV mass scale. In these proceedings the focus lies on reviewing these opportunities and sketching the current status of some pertinent searches.
↳ hep-exhep-ph14 citations
14*
Drag Induced Radiation and Multi-Stage Effects in Heavy-Flavor Energy Loss
Shanshan Cao🇺🇸 · Abhijit Majumder🇺🇸 · Guang-You Qin🇨🇳 · Chun Shen🇺🇸
It is argued that heavy-quarks traversing a Quark Gluon Plasma, undergo a multi-stage modification process, similar to the case of light flavors. Such an approach is applied to heavy-quark energy loss, which includes a rare-scattering, multiple emission formalism at momenta large compared to the mass (sensitive only to the transverse diffusion coefficient $q^$ ), and a single scattering induced emission formalism (Gunion-Bertsch) at momenta comparable to the mass of the quark [sensitive to $q^$ , and the longitudinal drag ( $e^$ ) and diffusion ( $e^_{2}$ ) coefficients]. The application of such a multi-stage approach within a 2+1D viscous fluid-dynamical simulation leads to simultaneous agreement with experimental data for the nuclear modification factor of both $B$ and $D$ mesons, as measured by the CMS collaboration at the LHC. The extracted transport coefficients are found to be consistent with those for light flavors.
↳ nucl-thhep-phnucl-exPLB(2019)·22 citations
15*
Long Short-Term Memory (LSTM) networks with jet constituents for boosted top tagging at the LHC
Shannon Egan🇨🇦 · Wojciech Fedorko🇨🇦 · Alison Lister🇨🇦 · Jannicke Pearkes🇺🇸 · Colin Gay🇨🇦
Multivariate techniques based on engineered features have found wide adoption in the identification of jets resulting from hadronic top decays at the Large Hadron Collider (LHC). Recent Deep Learning developments in this area include the treatment of the calorimeter activation as an image or supplying a list of jet constituent momenta to a fully connected network. This latter approach lends itself well to the use of Recurrent Neural Networks. In this work the applicability of architectures incorporating Long Short-Term Memory (LSTM) networks is explored. Several network architectures, methods of ordering of jet constituents, and input pre-processing are studied. The best performing LSTM network achieves a background rejection of 100 for 50% signal efficiency. This represents more than a factor of two improvement over a fully connected Deep Neural Network (DNN) trained on similar types of inputs.
↳ hep-excs.LGhep-phstat.ML81 citations
16*
Parton distribution amplitudes: revealing diquarks in the proton and Roper resonance
Cedric Mezrag🇮🇹 · Jorge Segovia🇪🇸 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸
We present the first quantum field theory calculation of the pointwise behaviour of the leading-twist parton distribution amplitudes (PDAs) of the proton and its lightest radial excitation. The proton's PDA is a broad, concave function, whose maximum is shifted relative to the peak in QCD's conformal limit expression for this PDA; an effect which signals the presence of both scalar and pseudovector diquark correlations in the nucleon, with the scalar generating around 60% of the proton's normalisation. The radial-excitation is constituted similarly, and the pointwise form of its PDA, which is negative on a material domain, is the result of marked interference between the contributions from both types of diquark; particularly, the locus of zeros that highlights its character as a radial excitation. These features originate with the emergent phenomenon of dynamical chiral-symmetry breaking in the Standard Model.
↳ nucl-thhep-lathep-phnucl-exPLB(2018)·45 citations
17*
Renormalised 3-point functions of stress tensors and conserved currents in CFT
Adam Bzowski🇧🇪 · Paul McFadden🇬🇧 · Kostas Skenderis🇬🇧
We present a complete momentum-space prescription for the renormalisation of tensorial correlators in conformal field theories. Our discussion covers all 3-point functions of stress tensors and conserved currents in arbitrary spacetime dimensions. In dimensions three and four, we give explicit results for the renormalised correlators, the anomalous Ward identities they obey, and the conformal anomalies. For the stress tensor 3-point function in four dimensions, we identify the specific evanescent tensorial structure responsible for the type A Euler anomaly, and show this anomaly has the form of a double copy of the chiral anomaly.
↳ hep-thhep-phJHEP(2018)·136 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.