118486980
CERN LHC signals for warped electroweak neutral gauge bosons
We study signals at the Large Hadron Collider (LHC) for Kaluza-Klein (KK) excitations of the electroweak gauge bosons in the framework with the standard model (SM) gauge and fermion fields propagating in a warped extra dimension. Such a framework addresses both the Planck-weak and flavor hierarchy problems of the SM. Unlike the often studied Z{sup '} cases, in this framework, there are three neutral gauge bosons due to the underlying SU(2){sub L}xSU(2){sub R}xU(1){sub X} gauge group in the bulk. Furthermore, couplings of these KK states to light quarks and leptons are suppressed, whereas those to top and bottom quarks are enhanced compared to the SM gauge couplings. Therefore, the production of light quark and lepton states is suppressed relative to other beyond the SM constructions, and the fermionic decays of these states are dominated by the top and bottom quarks, which are, though, overwhelmed by KK gluons dominantly decaying into them. However, as we emphasize in this paper, decays of these states to longitudinal W, Z and Higgs are also enhanced similarly to the case of top and bottom quarks. We show that the W, Z and Higgs final states can give significant sensitivity at the LHC to {approx}2(3) TeVmore » KK scale with an integrated luminosity of {approx}100 fb{sup -1} ({approx}1 ab{sup -1}). Since current theoretical framework(s) favor KK masses > or approx. 3 TeV, a luminosity upgrade of LHC is likely to be crucial in observing these states.« less
118328469
Collider Signatures for Heavy Lepton Triplet in Type I+III Seesaw
The minimal SU(5) theory augmented by the fermionic adjoint representation restores the coupling constant unification and gives realistic neutrino masses and mixing through the hybrid Type I and Type III seesaw. The crucial prediction of the theory is an SU(2) lepton triplet with the mass below TeV. We study the signature of these heavy leptons and propose the strategy to test this mechanism at the hadron and lepton colliders. The smoking gun evidence of the theory is Delta L=2 lepton number violation through events of a pair of like-sign leptons plus four jets without significant missing energy at hadron colliders. We find that via this unique channel, the heavy lepton can be searched for up to a mass of 200 GeV at the Tevatron with 8 fb^-1, and up to 450 (700) GeV at the LHC of 14 TeV C.M.energy with 10 (100) fb^-1. The signal rate at the 10 TeV LHC is reduced to 60-35% for a mass of 200-700 GeV. We also comment on how to distinguish this theory from other models with similar heavy leptons. Finally, we compare the production rates and angular distributions of heavy leptons in e+e- collisions for various models.
17175505
Higgs Signal for h $\to$ aa at Hadron Colliders
We assess the prospect of observing a neutral Higgs boson at hadron colliders in its decay to two spin-zero states, a, for a Higgs mass of 90-130 GeV, when produced in association with a W or Z boson. Such a decay is allowed in extensions of the MSSM with CP-violating interactions and in the NMSSM, and can dominate Higgs boson final states, thereby evading the LEP constraints on standard Higgs boson production. The light spin-zero state decays primarily via a→b and τ+τ−, so this signal channel retains features distinct from the main backgrounds. Our study shows that at the Tevatron, there may be potential to observe a few events in the bτ+τ− or bb channels with relatively small background, although this observation would be statistically limited. At the LHC, the background problem is more severe, but with cross sections and integrated luminosities orders of magnitude larger than at the Tevatron, the observation of a Higgs boson in this decay mode would be possible. The channel h→aa→bb would provide a large statistical significance, with a signal-to-background ratio on the order of 1:2. In these searches, the main challenge would be to retain the adequate tagging efficiency of b's and τ's in the low pT region.
118142307
Tevatron for LHC report: Higgs
The search for Higgs bosons in both the standard model and its extensions is well under way at the Tevatron. As the integrated luminosity collected increases into the multiple inverse femtobarn range, these searches are becoming very interesting indeed. Meanwhile, the construction of the Large Hadron Collider (LHC) and its associated experiments at CERN are nearing completion. In this TeV4LHC workshop, it was realized that any experience at the Tevatron with respect to backgrounds, experimental techniques and theoretical calculations that can be verified at the Tevatron which have relevance for future measurements at the LHC were important. Studies and contributions to these efforts were made in three broad categories: theoretical calculations of Higgs production and decay mechanisms; theoretical calculations and discussions pertaining to non-standard model Higgs bosons; and experimental reviews, analyses and developments at both the Tevatron and the upcoming LHC experiments. All of these contributions represent real progress towards the elucidation of the mechanism of electroweak symmetry breaking.
14072481
LHC signals for warped electroweak charged gauge bosons
We study signals at the LHC for the Kaluza-Klein (KK) excitations of electroweak charged gauge bosons in the framework of the standard model (SM) fields propagating in the bulk of a warped extra dimension. Such a scenario can solve both the Planck-weak and flavor hierarchy problems of the SM. There are two such charged states in this scenario with couplings to light quarks and leptons being suppressed relative to those in the SM, whereas the couplings to top/bottom quarks are enhanced, similar to the case of electroweak neutral gauge bosons previously studied. However, unlike the case of electroweak neutral gauge bosons, there is no irreducible QCD background (including pollution from possibly degenerate KK gluons) for decays to top+bottom final states so that this channel is useful for the discovery of the charged states. Moreover, decays of electroweak charged gauge bosons to longitudinal W, Z and Higgs are enhanced just as for the neutral bosons. However, unlike for the neutral gauge bosons, the purely leptonic (and hence clean) decay mode of the WZ is fully reconstructible so that the ratio of the signal to the SM (electroweak) background can potentially be enhanced by restricting to the resonance region more efficiently. Wemore » show that such final states can give sensitivity to 2(3) TeV masses with an integrated luminosity of 100(300) fb{sup -1}. We emphasize that improvements in discriminating a QCD jet from a highly boosted hadronically decaying W, and a highly boosted top jet from a bottom jet will enhance the reach for these KK particles, and that the signals we study for the warped extra dimensional model might actually be applicable also to a wider class of nonsupersymmetric models of electroweak symmetry breaking.« less
122909812
Precision measurements of B[ψ(3686)→π+π-J/ψ] and B[J/ψ→l+l-]
Based on (106.41 +/- 0.86) x 10(6) psi(3686) events collected with the BESIII detector at the BEPCII collider, the branching fractions of psi(3686) -> pi(+)pi(-)J/psi, J/psi -> e(+)e(-), and J/psi -> mu(+)mu(-) are measured. We obtain B[psi(3686) -> pi(+)pi(-)J/psi] = (34.98 +/- 0.02 +/- 0.45)%, B[J/psi -> e(+)e(-)] = (5.983 +/- 0.007 +/- 0.037)%, and B[J/psi -> mu(+)mu(-)] = (5.973 +/- 0.0007 +/- 0.038)%. The measurement of B[psi(3686) -> pi(+)pi(-)J/psi] confirms the CLEO-c measurement, and is apparently larger than the others. The measured J/psi leptonic decay branching fractions agree with previous experiments within one standard deviation. These results lead to B[J/psi -> l(+)l(-)] = (5.978 +/- 0.005 +/- 0.040)% by averaging over the e(+)e(-) and mu(+)mu(-) channels and a ratio of B[J/psi -> e(+)e(-)]/B[J/psi -> mu(+)mu(-)] = 1.0017 +/- 0.0017 +/- 0.0033, which tests e- mu universality at the four tenths of a percent level. All the measurements presented in this paper are the most precise in the world to date.
16285379
Observation of the Hadronic transitions chi(b1,2)(2P)-->omegaUpsilon(1S).
The CLEO Collaboration has made the first observations of hadronic transitions among bottomonium (bbmacr;) states other than the dipion transitions among Upsilon(nS) states. In our study of Upsilon(3S) decays, we find a significant signal for Upsilon(3S)-->gammaomegaUpsilon(1S) that is consistent with radiative decays Upsilon(3S)-->gammachi(b1,2)(2P), followed by chi(b1,2)(2P)-->omegaUpsilon(1S). The branching ratios we obtain are B[chi(b1)(2P)-->omegaUpsilon(1S)]=(1.63(+0.35+0.16)(-0.31-0.15))% and B[chi(b2)(2P)-->omegaUpsilon(1S)]=(1.10(+0.32+0.11)(-0.28-0.10))%, in which the first error is statistical and the second is systematic.
7127495
Precision measurement of the mass of the tau lepton
An energy scan near the tau pair production threshold has been performed using the BESIII detector. About 24 pb(-1) of data, distributed over four scan points, were collected. This analysis is based on t pair decays to ee, e mu, eh, h, hh, e.,. and p. final states, where h denotes a charged p or K. The mass of the t lepton is measured from a maximum likelihood fit to the t pair production cross- section data to be m(tau) = 1776.91 +/- 0.12_0.10 - 0.13 _ MeV/c(2), which is currently the most precise value in a single measurement.
7637272
Improved measurement of B(D+ --> mu+nu) and the pseudoscalar decay constant fD+.
We extract a relatively precise value for the decay constant of the meson by measuring B(D+ --> mu+nu) = (4.40 +/-0.66(+0.09)(-0.12) x 10(-4) using 281 pb(-1) of data taken on phi(3770) the resonance with the CLEO-c detector. We find fD+ = (222.6 +/- 16.7(+2.8)(-3.4)) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on B(D+e+nu)< 2.4 x 10(-5) which constrains new physics models.