HEP Phenomenology·hep-ph

Thu·Oct 29, 2015Thursday·October 29, 2015

29 papers—19 primary·10 cross-listed·reconstructed*

01*
The energy-momentum tensor and D-term of Q-clouds
Michael Cantara🇺🇸 · Manuel Mai🇺🇸 · Peter Schweitzer🇺🇸
The D-term is, like mass and spin, a fundamental property related to the energy-momentum tensor. Yet it is not known experimentally for any particle. In all theoretical studies so far the D-terms of various particles were found negative. Early works gave rise to the assumption the negative sign could be related to stability. The emerging question is whether it is possible to find a field-theoretical system with a positive D-term. To shed some light on this question we investigate Q-clouds, an extreme parametric limit in the Q-ball system. Q-clouds are classically unstable solutions which delocalize, spread out over all space forming an infinitely dilute gas of free quanta, and are even energetically unstable against tunneling to plane waves. In short, these extremely unstable field configurations provide an ideal candidate system for our purposes. By studying the energy-momentum tensor we show that at any stage of the Q-cloud limit one deals with perfectly well-defined and, when viewed in appropriately scaled coordinates, non-dissipating non-topological solitonic solutions. We investigate in detail their properties, and find new physical interpretations by observing that Q-clouds resemble BPS Skyrmions in certain aspects, and correspond to universal non-perturbative solutions in (complex) |\Phi|^4 theory. In particular, we show that also Q-cloud solutions have negative D-terms. Our findings do not prove that D-terms must always be negative. But they indicate that it is unlikely to realize a positive D-term in a consistent physical system.
hep-phNPA(2016)·26 citations
02*
Radiative corrections of $O (α)$ to $B^{-} \to V^{0} ℓ^{-} ν ˉ_{ℓ}$ decays
S. L. Tostado🇲🇽 · G. López Castro🇲🇽
The $O (α)$ electromagnetic radiative corrections to the $B^{-} \to V^{0} ℓ^{-} ν ˉ_{ℓ}$ ( $V$ is a vector meson and $ℓ$ a charged lepton) decay rates are evaluated using the cutoff method to regularize virtual corrections and incorporating intermediate resonance states in the real-photon amplitude to extend the region of validity of the soft-photon approximation. The electromagnetic and weak form factors of hadrons are assumed to vary smoothly over the energies of virtual and real photons under consideration. The cutoff dependence of radiative corrections upon the scale $Λ$ that separates the long- and short-distance regimes is found to be mild and is considered as an uncertainty of the calculation. Owing to partial cancellations of electromagnetic corrections evaluated over the three- and four-body regions of phase space, the photon-inclusive corrected rates are found to be dominated by the short-distance contribution. These corrections will be relevant for a precise determination of the $b$ quark mixing angles by testing isospin symmetry when measurements of semileptonic rates of charged and neutral $B$ mesons at the few percent level become available. For completeness, we also provide numerical values of radiative corrections in the three-body region of the Dalitz plot distributions of these decays.
hep-phEPJC(2016)·7 citations
03*
A New Scheme for NMSSM in Gauge Mediation
Masaki Asano🇩🇪 · Yuichiro Nakai🇺🇸 · Norimi Yokozaki🇮🇹
We propose a new framework for the next-to-minimal supersymmetric standard model (NMSSM) in gauge mediation, where in general the correct electroweak symmetry breaking (EWSB) is difficult to be explained. The difficulty is caused by the absence of a soft supersymmetry (SUSY) breaking mass for the NMSSM singlet S. In our framework, S is a meson in a hidden QCD. This QCD is responsible for the dynamical SUSY breaking, forming S, and the soft SUSY breaking mass for S, which is a key to explain the correct EWSB: all the ingredients for successful phenomenology originate from the common dynamics. From the requirement of the successful EWSB, the low-scale SUSY breaking around 100-1000 TeV is predicted. This is favored to avoid the large fine-tuning.
hep-phhep-exJHEP(2016)·1 citation
04*
Toward NNLL Resummation for Hadron Production in Hadronic Collisions
Patriz Hinderer🇩🇪 · Felix Ringer🇺🇸 · George F. Sterman🇺🇸 · Werner Vogelsang🇩🇪
We present results relevant for the extension of threshold resummation beyond the next-to-leading logarithmic (NLL) order for QCD hard-scattering processes. As an example, we consider di-hadron production $H_{1} H_{2} \to h_{1} h_{2} X$ , where the produced pair has a large invariant mass. Taking into account the non-trivial color structure of the partonic hard-scattering process, we determine the hard and soft matrices in color space. In our numerical studies we find a significant improvement compared to previous results at NLL accuracy. In particular, the scale dependence of the resummed cross section is greatly reduced. In addition, we comment on the extension of the techniques developed in this work to other observables relevant for hadronic collisions.
hep-phPoS(2015)·1 citation
05*
Production Regimes for Self-Interacting Dark Matter
Nicolas Bernal🇧🇷 · Xiaoyong Chu🇮🇹 · Camilo Garcia-Cely🇧🇪 · Thomas Hambye🇧🇪 · Bryan Zaldivar🇧🇪
In the context of Self-Interacting Dark Matter as a solution for the small-scale structure problems, we consider the possibility that Dark Matter could have been produced without being in thermal equilibrium with the Standard Model bath. We discuss one by one the following various dark matter production regimes of this kind: freeze-in, reannihilation and dark freeze-out. We exemplify how these mechanisms work in the context of the particularly simple Hidden Vector Dark Matter model. In contrast to scenarios where there is thermal equilibrium with the Standard Model bath, we find two regimes which can easily satisfy all the laboratory and cosmological constraints. These are dark freeze-out with 3-to-2 annihilations and freeze-in via a light mediator. In the first regime, different temperatures in the visible and the Dark Matter sectors allow us to avoid the constraints coming from cosmic structure formation as well as the use of non-perturbative couplings to reproduce the observed relic density. For the second regime, different couplings are responsible for Dark Matter relic density and self-interactions, permitting to surpass BBN, X-ray, CMB and direct detection constraints.
hep-phJCAP(2016)·193 citations
06*
Compressing the Inert Doublet Model
Nikita Blinov🇺🇸 · Jonathan Kozaczuk🇨🇦 · David E. Morrissey🇨🇦 · Alejandro de la Puente🇨🇦
The Inert Doublet Model relies on a discrete symmetry to prevent couplings of the new scalars to Standard Model fermions. This stabilizes the lightest inert state, which can then contribute to the observed dark matter density. In the presence of additional approximate symmetries, the resulting spectrum of exotic scalars can be compressed. Here, we study the phenomenological and cosmological implications of this scenario. We derive new limits on the compressed Inert Doublet Model from LEP, and outline the prospects for exclusion and discovery of this model at dark matter experiments, the LHC, and future colliders.
hep-phPRD(2016)·56 citations
07*
GM2Calc: Precise MSSM prediction for $(g - 2)$ of the muon
Peter Athron🇦🇺 · Markus Bach🇩🇪 · Helvecio G. Fargnoli🇧🇷 · Christoph Gnendiger🇩🇪 · Robert Greifenhagen🇩🇪 · Jae-hyeon Park🇪🇸 · Sebastian Paßehr🇩🇪 · Dominik Stöckinger🇩🇪 · Hyejung Stöckinger-Kim🇩🇪 · Alexander Voigt🇩🇪
We present GM2Calc, a public C++ program for the calculation of MSSM contributions to the anomalous magnetic moment of the muon, $(g - 2)_{μ}$ . The code computes $(g - 2)_{μ}$ precisely, by taking into account the latest two-loop corrections and by performing the calculation in a physical on-shell renormalization scheme. In particular the program includes a $tan β$ resummation so that it is valid for arbitrarily high values of $tan β$ , as well as fermion/sfermion-loop corrections which lead to non-decoupling effects from heavy squarks. GM2Calc can be run with a standard SLHA input file, internally converting the input into on-shell parameters. Alternatively, input parameters may be specified directly in this on-shell scheme. In both cases the input file allows one to switch on/off individual contributions to study their relative impact. This paper also provides typical usage examples not only in conjunction with spectrum generators and plotting programs but also as C++ subroutines linked to other programs.
hep-phEPJC(2016)·104 citations
08*
Finite Numbers of Sources, Particle Correlations and the Color Glass Condensate
Larry McLerran🇺🇸 · Vladimir Skokov🇺🇸
We show that for a finite number of emitting sources, the Color Glass Condensate produces substantial elliptic azimuthal anisotropy, characterized by $v_{2}$ , for two and four particle correlations for momentum greater than or of the order the saturation momentum. The flow produced has the correct semi-quantitative features to describe flow seen in LHC experiments with p-Pb and pp collisions. This flow is induced by quantum mechanical interference between the waves of produced particles, and the flow itself is coupled to fluctuations in the positions of emitting sources. We shortly discuss generalizing these results to odd $v_{n}$ , to correlations involving larger number of particles, and to transverse momentum scales $Λ_{QCD} ≪ p_{T} ≪ Q_{sat}$ .
hep-phNPA(2016)·23 citations
09*
A 2 TeV $W_{R}$ , Supersymmetry, and the Higgs Mass
Jack H Collins🇺🇸 · Wee Hao Ng🇺🇸
A recent ATLAS search for diboson resonances and a CMS search for $ee j j$ resonances which both show excesses with significance around 3 sigma have generated interest in $S U (2)_{R}$ gauge extensions of the Standard Model with a $W^{'}$ mass around 2 TeV. We investigate the possibility that an $S U (2)_{R}$ gauge extension of the MSSM compatible with an explanation of the diboson anomaly might give rise to a significant enhancement of the Higgs mass above the MSSM tree level bound $m_{h, tree} < 90 GeV$ due to non-decoupling D-terms. This model contains a vector-like charge -1/3 $S U (2)_{R}$ singlet quark for each generation which mixes significantly with the $S U (2)_{R}$ doublet quarks, affecting the $W_{R}$ phenomenology. We find that it is possible to achieve $m_{h, tree} > 110 GeV$ , and this requires that the $Z^{'}$ mass is close to 3 TeV.
hep-phhep-exJHEP(2016)·28 citations
10*
Prospects for $γ γ \to H$ and $γ γ \to W^{+} W^{-}$ measurements at the FCC-ee
Patricia Rebello Teles🇧🇷 · David d'Enterria🇨🇭
We study the possibilities for the measurement of two-photon production of the Higgs boson (in the $b b ˉ$ decay channel), and of $W^{+} W^{-}$ pairs (decaying into four jets) in $e^{+} e^{-}$ collisions at the the Future Circular Collider (FCC-ee). The processes are simulated with the PYTHIA and MADGRAPH 5 Monte Carlo codes, using the effective photon approximation for the $e^{+} e^{-}$ photon fluxes, at center-of-mass energies $s =$ 160 GeV and 240 GeV. The analyses include electron-positron tagging, realistic acceptance and reconstruction efficiencies for the final-state jets, and selection criteria to remove the backgrounds. Observation of both channels is achievable with the expected few ab $^{- 1}$ integrated luminosities at FCC-ee.
hep-phhep-ex6 citations
11*
Conformal Barrier and Hidden Local Symmetry Constraints: Walking Technirhos in LHC Diboson Channels
Hidenori S. Fukano🇯🇵 · Shinya Matsuzaki🇯🇵 · Koji Terashi🇯🇵 · Koichi Yamawaki🇯🇵
We expand the previous analyses of the conformal barrier on the walking technirho for the 2 TeV diboson excesses reported by the ATLAS collaboration, with a special emphasis on the hidden local symmetry (HLS) constraints. We first show that the Standard Model (SM) Higgs Lagrangian is equivalent to the scale-invariant nonlinear chiral Lagrangian, which is further gauge equivalent to the scale-invariant HLS model, with the scale symmetry realized nonlinearly via SM Higgs as a (pseudo-) dilaton. The scale symmetry forbids the new vector boson decay to the 125 GeV Higgs plus W/Z boson, in sharp contrast to the conventional "equivalence theorem" which is invalidated by the conformality. The HLS forbids mixing between the iso-triplet technirho's, rho_{Pi} and rho_{P}, of the one-family walking technicolor (with four doublets N_D=N_F/2=4), which, without the HLS, would be generated when switching on the standard model gauging. We also present updated analyses of the walking technrho's for the diboson excesses by fully incorporating the constraints from the conformal barrier and the HLS as well as possible higher order effects: still characteristic of the one-family walking technirho is its smallness of the decay width, roughly of order Gamma/M_rho ~ [3/N_C x 1/N_D] x [Gamma/M_rho]_{QCD} ~ 70 GeV/2TeV (N_D= N_C=4), in perfect agreement with the expected diboson resonance with Gamma<100 GeV. The model is so sharply distinguishable from other massive spin 1 models without the conformality and HLS that it is clearly testable at the LHC Run II. If the 2 TeV boson decay to WH/ZH is not observed in the ongoing Run II, then the conformality is operative on the 125 GeV Higgs, strongly suggesting that the 2 TeV excess events are responsible for the walking technirhos and the 125 GeV Higgs is the technidilaton.
hep-phhep-exNPB(2016)·22 citations
12*
Note on the standard model as an effective theory
Amir H. Fariborz🇺🇸 · Renata Jora🇷🇴
We present a criterion of consistency derived from the analogy between the partition function of a quantum field theory and that of a statistical system. Based on this we examine a new class of higher dimension operators that might act in the standard model.
hep-ph2 citations
13*
About the particle structure and content of the standard model
Renata Jora🇷🇴
We determine the number and distribution of the fermion states in the standard model based on the possible fermion representations of the gauge bosons. By extracting the even parity scalars from the fermion states we suggest the existence of multiple Higgses arranged in suitable singlets or multiplets of $S U (3)_{L}$ and $S U (3)_{c}$ .
hep-ph0 citations
14*
Probing CP violation signal at DUNE in presence of non-standard neutrino interactions
Mehedi Masud🇮🇳 · Animesh Chatterjee🇺🇸 · Poonam Mehta🇮🇳
We discuss the impact of non-standard neutrino matter interactions (NSI) in propagation on the determination of CP phase in the context of the long baseline accelerator experiments such as Deep Underground Neutrino Experiment (DUNE). DUNE will mainly address the issue of CP violation in the leptonic sector. Here we study the role of NSI and its impact on the question of observing the CP violation signal at DUNE. We consider two scenarios of oscillation with three active neutrinos in absence and presence of NSI. We elucidate the importance of ruling out subdominant new physics effects introduced by NSI in inferring CP violation signal at DUNE by considering NSI terms collectively as well as by exploiting the non-trivial interplay of moduli and phases of the NSI terms. We demonstrate the existence of NSI-SI degeneracies which need to be eliminated in reliable manner in order to make conclusive statements about the CP phase.
hep-phJ.Phys.G(2016)·107 citations
15*
Radiative transitions of charmonium states in a constituent quark model
Wei-Jun Deng🇨🇳 · Li-Ye Xiao🇨🇳 · Long-Cheng Gui🇨🇳 · Xian-Hui Zhong🇨🇳
We study the electromagnetic (EM) transitions of the $n S$ , $n P$ ( $n \leq 3$ ), and $n D$ ( $n \leq 2$ ) charmonium states with a constituent quark model. We obtain a reasonable description of the EM transitions of the well-established charmonium states $J / ψ$ , $ψ (2 S)$ , $χ_{c J} (1 P)$ , $h_{c} (1 P)$ and $ψ (3770)$ . We find that the M2 transitions give notable corrections to some E1 dominant processes by interfering with the E1 transitions. Our predictions of EM decay properties for the higher charmonium states are also presented and compared with other model predictions. In particular, we discuss the EM decay properties of some $" X Y Z "$ states, such as $X (3823)$ , $X (3872)$ , $X (3915)$ , $X (3940)$ and $X (4350)$ as conventional charmonium states. Assuming $X (3872)$ as the $χ_{c 1} (2 P)$ state, our predicted ratio $Γ [X (3872) \to ψ (2 S) γ] /Γ [X (3872) \to J / ψ γ] ≃ 4.0$ is consistent with BaBar's measurement.
hep-phhep-exnucl-th13 citations
16*
Triple Higgs coupling in the most general 2HDM at SM-like scenario
Ilya Ginzburg🇷🇺
We consider the triple Higgs coupling for $h (125)$ Higgs boson within the most general 2HDM. At moderate values of parameters of model, allowing by modern data, noticeable deviation of this coupling from its SM value is improbable. This deviation can be sizable only if some measurable parameters of the model are exotic.
hep-phEPJC(2017)·21 citations
17*
Poincare covariant pseudoscalar and scalar meson spectroscopy in Wigner-Weyl phase
Thomas Hilger🇦🇹
The coupled quark Dyson-Schwinger and meson Bethe-Salpeter equations in rainbow-ladder truncation for spin-0 mesons are solved in Wigner-Weyl phase in the chiral limit and beyond, retaining only the ultraviolet finite terms of the phenomenologically most successful Maris-Tandy interaction. This allows to reveal and discuss the scalar and pseudoscalar meson masses in a chirally symmetric setting without additional medium effects. Independent of the current-quark mass, the found solutions are spacelike, i.\,e.\ have negative squared masses. The current-quark mass dependence of meson masses, leptonic decay constants and chiral condensate are illustrated in Wigner-Weyl phase.
hep-phPRD(2016)·12 citations
18*
Properties of Excited Charm and Charm-Strange Mesons
Stephen Godfrey🇨🇦 · Kenneth Moats (Carleton University)🇨🇦
We calculate the properties of excited charm and charm-strange mesons. We use the relativized quark model to calculate their masses and wavefunctions that are used to calculate radiative transition partial widths and the $^{3} P_{0}$ quark-pair-creation model to calculate their strong decay widths. We use these results to make quark model spectroscopic assignments for recently observed charm and charm-strange mesons. In particular we find that the properties of the $D_{J} (2550)^{0}$ and $D_{J}^{*} (2600)^{0}$ are consistent with those of the $2^{1} S_{0} (c u ˉ)$ and the $2^{3} S_{1} (c u ˉ)$ states respectively, the $D_{1}^{*} (2760)^{0}$ , $D_{3}^{*} (2760)^{-}$ , and $D_{J} (2750)^{0}$ with those of the $1^{3} D_{1} (c u ˉ)$ , $1^{3} D_{3} (d c ˉ)$ , and $1 D_{2} (c u ˉ)$ states respectively. We tentatively identify the $D_{J}^{*} (3000)^{0}$ as the $1^{3} F_{4} (c u ˉ)$ and favour the $D_{J} (3000)^{0}$ to be the $3^{1} S_{0} (c u ˉ)$ although we do not rule out the $1 F_{3}$ and $1 F_{3}^{'}$ assignment. For the recently observed charm-strange mesons we identify the $D_{s 1}^{*} (2709)^{\pm}$ , $D_{s 1}^{*} (2860)^{-}$ , and $D_{s 3}^{*} (2860)^{-}$ as the $2^{3} S_{1} (c s ˉ)$ , $1^{3} D_{1} (s c ˉ)$ , and $1^{3} D_{3} (s c ˉ)$ states respectively and suggest that the $D_{s J} (3044)^{\pm}$ is most likely the $D_{s 1} (2 P_{1}^{'})$ or $D_{s 1} (2 P_{1})$ states although it might be the $D_{s 2}^{*} (2^{3} P_{2})$ with the $D K$ final state too small to be observed with current statistics. Based on the predicted properties of excited states, that they not have too large a total width and they have a reasonable branching ratio to simple final states, we suggest states that should be able to be found in the near future. We expect that the tables of properties summarizing our results will be useful for interpreting future observations of charm and charm-strange mesons.
hep-phhep-exPRD(2016)·225 citations
19*
Geometrical Models and Hadronic Radii
Sarwat Zahra🇵🇰 · Haris Rashid🇵🇰 · Fazal-e-Aleem · Talab Hussain🇵🇰 · Abrar Ahmad Zafar🇵🇰 · Sohail Afzal Tahir🇵🇰
By using electromagnetic form factors predicted by Generalized Chou Yang model (GCYM), we compute root mean square (rms) radii of several hadrons with varying strangeness content (number of strange quarks/anti-quarks) such as (pion, proton, phi0, Lambda0, Sigma+, Sigma- and Omega-) The computed radii are found quite consistent with the experimental results and those from other models (for pion and proton). For hadrons other than pion and proton, the experimental results are not available and also the GCYM and other models results are not consistent with each other. The computed rms radii (from GCYM and other models) indicate that rms radii decrease with increase in strangeness content, separately for mesons and baryons. The experimental results of hadrons other than pion and proton will throw more light on the suitability of GCYM and other models.
hep-phnucl-th2 citations
20*
Lattice computation of the nucleon scalar quark contents at the physical point
S. Durr🇩🇪 · Z. Fodor🇩🇪 · C. Hoelbling🇩🇪 · S. D. Katz🇭🇺 · S. Krieg🇩🇪 · L. Lellouch🇫🇷 · T. Lippert🇩🇪 · T. Metivet🇫🇷 · A. Portelli🇫🇷 · K. K. Szabo🇩🇪 · C. Torrero🇫🇷 · B. C. Toth🇩🇪 · L. Varnhorst🇩🇪
We present a QCD calculation of the $u$ , $d$ and $s$ scalar quark contents of nucleons based on $47$ lattice ensembles with $N_{f} = 2 + 1$ dynamical sea quarks, $5$ lattice spacings down to $0.054 fm$ , lattice sizes up to $6 fm$ and pion masses down to $120 MeV$ . Using the Feynman-Hellmann theorem, we obtain $f_{u d}^{N} = 0.0405 (40) (35)$ and $f_{s}^{N} = 0.113 (45) (40)$ , which translates into $σ_{π N} = 38 (3) (3) MeV$ , $σ_{s N} = 105 (41) (37) MeV$ and $y_{N} = 0.20 (8) (8)$ for the sigma terms and the related ratio, where the first errors are statistical and the second are systematic. Using isospin relations, we also compute the individual up and down quark contents of the proton and neutron (results in the main text).
↳ hep-lathep-phPRL(2016)·163 citations
21*
Marginal Breaking of Conformal SUSY QCD
Kevin F. Cleary🇺🇸 · John Terning🇺🇸
We provide an example of a 4D theory that exhibits the Contino-Pomarol-Rattazzi mechanism, where breaking conformal symmetry by an almost marginal operator leads to a light pseudo-Goldstone boson, the dilaton, and a parametrically suppressed contribution to vacuum energy. We consider SUSY QCD at the edge of the conformal window and break conformal symmetry by weakly gauging a subgroup of the flavor symmetry. Using Seiberg duality we show that for a range of parameters the singlet meson in the dual theory reaches the unitarity bound, however, this theory does not have a stable vacuum. We stabilize the vacuum with soft breaking terms, compute the mass of the dilaton, and determine the range of parameters where the leading contribution to the dilaton mass is from the almost marginal coupling.
↳ hep-thhep-phJHEP(2016)·2 citations
22*
Current status of dynamical modeling of fluctuations at the QCD phase transition in heavy-ion collisions
Marlene Nahrgang🇺🇸
For a complete understanding of the QCD phase diagram it is important to connect first-principle thermodynamic calculations to experimental data from the RHIC Beam Energy Scan and the future experimental facilities FAIR, GSI, and NICA, Dubna. This can only be achieved by a realistic modeling of the dynamical evolution of critical fluctuations in heavy-ion collisions at the QCD phase transition. In this note I will summarize the current status of these dynamical models and highlight some of the important issues, which need to be addressed in the future.
↳ nucl-thhep-phPoS(2015)·7 citations
23*
Effective Field Theory of Dark Matter from membrane inflationary paradigm
Sayantan Choudhury🇮🇳 · Arnab Dasgupta🇮🇳
In this article, we have studied the cosmological and particle physics constraints on dark matter relic abundance from effective field theory of inflation using tensor-to-scalar ratio ( $r$ ), in case of Randall-Sundrum single membrane (RSII) paradigm. Using semi-analytical approach we establish a direct connection between the dark matter relic abundance ( $Ω_{D M} h^{2}$ ) and primordial gravity waves ( $r$ ), which establishes a precise connection between inflation and generation of dark matter within the framework of effective field theory in RSII membrane. Further assuming the UV completeness of the effective field theory perfectly holds good in the prescribed framework, we have explicitly shown that the membrane tension, $σ$ , bulk mass scale $M_{5}$ , and cosmological constant $Λ ~_{5}$ , in RSII membrane plays the most significant role to establish the connection between dark matter and inflation, using which we have studied the features of various mediator mass scale suppressed effective field theory "relevant operators" induced from the localized $s$ , $t$ and $u$ channel interactions. Taking a completely model independent approach, we have studied an exhaustive list of tree-level Feynman diagrams for dark matter annihilation within the prescribed setup and to check the consistency of the obtained results, further we apply the constraints as obtained from recently observed Planck 2015 data and Planck+BICEP2+Keck Array joint datasets. Using all of these derived results we have shown that to satisfy the bound on, $Ω_{D M} h^{2} = 0.1187 \pm 0.0017$ , as from Planck 2015 data, it is possible to put further stringent constraint on $r$ within, $0.01 \leq r \leq 0.12$ , for thermally averaged annihilation cross-section of dark matter, $⟨ σ v ⟩ \approx O (1 0^{- 28} - 1 0^{- 27}) c m^{3} /s$ , which are very useful to constrain various membrane inflationary models.
↳ hep-thastro-ph.COgr-qchep-phPhys.Dark Univ.(2016)·12 citations
24*
Infinite efficiency of collisional Penrose process: Can over-spinning Kerr geometry be the source of ultra-high-energy cosmic rays and neutrinos ?
Mandar Patil🇯🇵 · Tomohiro Harada🇯🇵 · Ken-ichi Nakao🇯🇵 · Pankaj S. Joshi🇮🇳 · Masashi Kimura🇬🇧
The origin of the ultra-high-energy particles we receive on the Earth from the outer space such as EeV cosmic rays and PeV neutrinos remains an enigma. All mechanisms known to us currently make use of electromagnetic interaction to accelerate charged particles. In this paper we propose a mechanism exclusively based on gravity rather than electromagnetic interaction. We show that it is possible to generate ultra-high-energy particles starting from particles with moderate energies using the collisional Penrose process in an overspinning Kerr spacetime transcending the Kerr bound only by an infinitesimal amount, i.e., with the Kerr parameter $a = M (1 + ϵ)$ , where we take the limit $ϵ \to 0^{+}$ . We consider two massive particles starting from rest at infinity that collide at $r = M$ with divergent center-of-mass energy and produce two massless particles. We show that massless particles produced in the collision can escape to infinity with the ultra-high energies exploiting the collisional Penrose process with the divergent efficiency $η \sim 1 / ϵ \to \infty$ . Assuming the isotropic emission of massless particles in the center-of-mass frame of the colliding particles, we show that half of the particles created in the collisions escape to infinity with the divergent energies. To a distant observer, ultra-high-energy particles appear to originate from a bright spot which is at the angular location $ξ \sim 2 M / r_{o b s}$ with respect to the singularity on the side which is rotating towards the observer. We show that the anisotropy in emission in the center-of-mass frame, which is dictated by the differential cross-section of underlying particle physics process, leaves a district signature on the spectrum of ultra-high-energy massless particles. Thus, it provides a unique probe into fundamental particle physics.
↳ gr-qcastro-ph.HEhep-phhep-thPRD(2016)·33 citations
25*
Fluctuations of flow harmonics in Pb+Pb collisions at $s_{N N} = 2.76$ ~TeV from the Glauber model
Maciej Rybczynski🇵🇱 · Wojciech Broniowski🇵🇱
In the framework of the Glauber model as implemented in GLISSANDO 2, we study the fluctuations of flow harmonics in Pb+Pb collisions at the LHC centre-of-mass energy of 2.76 TeV. The model with wounded nucleons and the admixture of binary collisions leads to reasonable agreement for the ellipticity and triangularity fluctuations with the experimental data from the ATLAS, ALICE, and CMS collaborations, verifying the assumption that the initial eccentricity is approximately proportional to the harmonic flow of charged particles. While the agreement, in particular at the level of event-by-event distributions of eccentricities/flow coefficients in not perfect, it leads to a fair (at the level of a few percent for all centralities except the most peripheral collisions) description of the scaled standard deviation and the F measure which involve the four-particle cumulants. We also discuss the case of quadrangular flow. Computer scripts that generate our results from the GLISSANDO 2 simulations are provided.
↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2016)·10 citations
26*
Spin precession in anisotropic cosmologies
A.Yu. Kamenshchik🇮🇹 · O.V. Teryaev🇷🇺
We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early Universe may produce the sterile particles contributing to dark matter.
↳ gr-qcastro-ph.COhep-phhep-thEPJC(2016)·4 citations
27*
FCC based ep and $μ$ p colliders
Y. C. Acar🇹🇷 · U. Kaya🇹🇷 · B. B. Oner🇹🇷 · S. Sultansoy🇹🇷
Construction of future electron-positron colliders (or dedicated electron linac) and muon colliders close to Future Circular Collider will give opportunity to utilize highest energy proton and nucleus beams for lepton-hadron and photon-hadron collisions. In this paper we estimate main parameters of the FCC based ep and \mu p colliders.
↳ hep-exhep-phphysics.acc-ph10 citations
28*
How scalar-field dark matter may conspire to facilitate baryogenesis at the electroweak scale
Tanja Rindler-Daller🇺🇸 · Bohua Li🇺🇸 · Paul R. Shapiro🇺🇸 · Marek Lewicki🇵🇱 · James D. Wells🇺🇸
The cosmic evolution of a dark matter model which behaves relativistically in the early Universe is explored. Dark matter is described as a complex scalar field, whose earliest evolution is characterized by a stiff equation of state ( $p ≃ ρ$ ). In this phase, it is the dominant component in the Universe. We present constraints from Big Bang nucleosynthesis and primordial gravity waves from inflation. Also, we study how the associated enhanced expansion rate due to the stiff phase might facilitate a first-order electroweak symmetry breaking phase transition, in light of the recently measured value of the Higgs boson mass.
↳ astro-ph.COgr-qchep-ph4 citations
29*
Direct calculation of hadronic light-by-light scattering
Jeremy Green🇩🇪 · Nils Asmussen🇩🇪 · Oleksii Gryniuk🇩🇪 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Andreas Nyffeler🇩🇪 · Vladimir Pascalutsa🇩🇪
We report calculations of hadronic light-by-light scattering amplitudes via lattice QCD evaluation of Euclidean four-point functions of vector currents. These initial results include only the fully quark-connected contribution. Particular attention is given to the case of forward scattering, which can be related via dispersion relations to the $γ^{*} γ^{*} \to$ hadrons cross section, and thus allows lattice data to be compared with phenomenology. We also present a strategy for computing the hadronic light-by-light contribution to the muon anomalous magnetic moment.
↳ hep-lathep-phnucl-thPoS(2016)·42 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.