118538298
Exclusive heavy quarkonium + γ production from e+e-annihilation into a virtual photon
We compute the cross section for exclusive production of a photon associated with a heavy quarkonium H of charge-conjugation parity C=+1 from e{sup +}e{sup -} annihilation into a virtual photon at the center-of-momentum energy {radical}(s)=10.58 GeV. The nonrelativistic QCD factorization formulas for the differential and total cross sections are obtained at leading order in the strong coupling and in the relative velocity of the heavy quark in the quarkonium rest frame. The predicted cross sections for the S-wave spin-singlet cases are about 80 fb and 50 fb for H={eta}{sub c} and {eta}{sub c}(2S), respectively. Among P-wave spin-triplet charmonia, {chi}{sub c1} has a particularly large cross section of about 14 fb. The cross sections for bottomonium states {eta}{sub b} and {chi}{sub bJ} are about 3 fb. A rough estimate of the background reveals that the signal significances for charmonium processes are sufficiently large enough to be detected with ease with the integrated luminosities available at the present B factories.
118370194
Inclusive double-quarkonium production at the Large Hadron Collider
Based on the nonrelativistic QCD (NRQCD) factorization formalism, we investigate inclusive productions of two spin-triplet S-wave quarkonia pp → 2J/ψ + X, 2Υ + X, and J/ψ + Υ + X at the CERN Large Hadron Collider. The total production rates integrated over the rapidity (y) and transverse-momentum (pT) ranges |y| < 2.4 and pT< 50GeV are predicted to be σ[pp → 2J/ψ + X] = 22 (35) nb, σ[pp → 2Υ + X ]= 24 (49) pb, and σ[pp → J/ψ + Υ + X ] = 7 (13) pb at the center-of-momentum energy $ \sqrt {s} = 7\left( {14} \right)\;{\text{TeV}} $. In order to provide predictions that can be useful in both small- and large-pT regions, we do not employ the fragmentation approximation and we include the spin-triplet S-wave color-singlet and color-octet channels for each quarkonium final state at leading order in the strong coupling. The pT distributions of pp → 2J/ψ + X and 2Υ + X in the low-pT region are dominated by the color-singlet contributions. At leading order in the strong coupling, the color-singlet channel is absent for pp → J/ψ + Υ + X. Therefore, the process pp → J/ψ + Υ + X may provide a useful probe to the color-octet mechanism of NRQCD.
2104658
Inclusive S-wave charmonium productions in B decays.
The inclusive {ital S}-wave charmonium production rates in {ital B} decays are considered using the Bodwin-Braaten-Lepage approach, including the relativistic corrections and the color-octet mechanism suggested as a possible solution to the {psi}{prime} puzzle at the Fermilab Tevatron. We first consider relativistic and radiative corrections to {ital J}/{psi}{r_arrow}{ital e}{sup +}{ital e}{sup {minus}} and {ital J}/{psi}{r_arrow} light hadrons (LH{close_quote}s), in order to determine two nonperturbative parameters, {l_angle}{ital J}/{psi}{parallel}{ital O}{sub 1}({sup 3}{ital S}{sub 1}){parallel}{ital J}/{psi}{r_angle}, {l_angle}{ital J}/{psi}{parallel}{ital P}{sub 1}({sup 3}{ital S}{sub 1}){parallel}{ital J}/{psi}{r_angle}, in the factorization formulas for these decays. Using these two matrix elements and including the color-octet {ital c{bar c}}({sup 3}{ital S}{sub 1}) state contribution, we get a moderate increase in the decay rates for {ital B} decays into {ital J}/{psi} (or {psi}{prime})+{ital X}. Our results {ital B}({ital B}{r_arrow}{ital J}/{psi} (or {psi}{prime})+{ital X})=0.58 (0.23){percent} for {ital M}{sub {ital b}}=5.3 GeV get closer to the recent CLEO data. As a by-product, we prefer a larger decay rate for {eta}{sub {ital c}}{r_arrow}LH compared to the present data. {copyright} {ital 1996 The American Physical Society.}
209521249
Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton-proton collisions at √s=7 TeV with the ATLAS detector
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for events containing one or more such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at root s = 7 TeV corresponding to an integrated luminosity of 4.4 fb(-1) collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are set on the production cross section for pair production of supersymmetric particles, multiplied by the square of the branching fraction for a neutralino to decay to charged hadrons and a muon, based on the scenario where both of the produced supersymmetric particles give rise to neutralinos that decay in this way. However, since the search strategy is based on triggering on and reconstructing the decay products of individual long-lived particles, irrespective of the rest of the event, these limits can easily be reinterpreted in scenarios with different numbers of long-lived particles per event. The limits are presented as a function of neutralino lifetime, and for a range of squark and neutralino masses.
119097109
Model independent analysis of the forward–backward asymmetry of top quark production at the Tevatron
Abstract Motivated by a possible anomaly in the forward–backward (FB) asymmetry of top quark ( A FB ) observed at the Tevatron, we perform a model independent analysis on q q ¯ → t t ¯ using an effective Lagrangian with dim-6 four-quark operators. We derive necessary conditions on new physics structures and the couplings that are consistent with the t t ¯ production cross section and A FB measured at the Tevatron, and discuss possible new physics scenarios that could generate such dim-6 operators.
118558040
IS DARK ENERGY FROM COSMIC HAWKING RADIATION
It is suggested that dark energy is the energy of the Hawking radiation from a cosmic horizon. Despite its extremely low Gibbons–Hawking temperature, this radiation could have the appropriate magnitude $O(M^2_{\rm P}H^2)$and the equation of state to explain the observed cosmological data if there is a Planck scale UV-cutoff, where H is the Hubble parameter.
113405504
He I D3 Observations of the 1984 May 22 M6.3 Solar Flare
The He I D3 line has a unique response to a flare impact on the low solar atmosphere and can be a powerful diagnostic tool for energy transport processes. Using images obtained from the recently digitized films of the Big Bear Solar Observatory, we report D3 observations of the M6.3 flare on 1984 May 22, which occurred in an active region with a circular magnetic polarity inversion line (PIL). The impulsive phase of the flare starts with a main elongated source that darkens in D3, inside of which bright emission kernels appear at the time of the initial small peak in hard X-rays (HXRs). These flare cores subsequently evolve into a sharp emission strand lying within the dark halo; this evolution occurs at the same time as the main peak in HXRs, reversing the overall source contrast from ?5% to 5%. The radiated energy in D3 during the main peak is estimated to be about 1030 erg, which is comparable to that carried by nonthermal electrons above 20?keV. Afterward, the flare proceeds along the circular PIL in the counterclockwise direction to form a dark circular ribbon in D3, which apparently mirrors the bright ribbons in H? and He I 10830 ?. All of these ribbons last for over one hour in the late gradual phase. We suggest that the present event resembles the so-called black-light flare that was proposed based on continuum images, and that D3 darkening and brightening features herein may be due to thermal conduction heating and the direct precipitation of high-energy electrons, respectively.
11251914
Measurement of strange quark contributions to the vector form factors of the proton at Q2 = 0.22 (GeV / c)2.
A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q;{2} = 0.22 (Ge V / c);{2} is reported here. The measured asymmetry is A_{LR} = (-17.23 +/- 0.82_{stat} +/- 0.89_{syst}) x 10;{-6}. The standard model prediction assuming no strangeness is A_{0} = (-15.87 +/- 1.22) x 10;{-6}. In combination with previous results from measurements at forward angles, it is possible to disentangle for the first time the strange form factors at this momentum transfer, G_{E};{s} = 0.050 +/- 0.038 +/- 0.019 and G_{M};{s} = -0.14 +/- 0.11 +/- 0.11.