3,814 research outputs found
ZγH Vertex Effects at Future Colliders
No full textWe show that the Higgs production in e gamma collisions, through the one-loop reaction e gamma \to eH at large transverse momentum, can provide a precise determination of the Z gamma H vertex. We concentrate on the analysis of signal rates vs background looking for strategies to improve the ratio S/B. Possible bounds on anomalous contributions to the Z gamma H vertex are derived
The ATLAS Insertable B-layer
No full textThe ATLAS Insertable B-Layer (the IBL) will be inserted into ATLAS before the startup of the LHC Run 2. It consists of an assembly of pixel detectors to be mounted very close to the interaction point of ATLAS, together with a new beam pipe with a smaller radius than the one used in run 1. This talk presents the IBL detector, with emphasis on the improvements of sensor and readout technologies that have been developed in order to satisfy the requirements for proper operation of the IBL in Run 2
Summary on tau leptonic branching ratios and universality
No full textThe large samples of tau decays available from CLEO and the four LEP experiment have resulted in new, precise measurements of the leptonic branching ratios of the tau . The experimental techniques to obtain these results are reviewed with special emphasis on the DELPHI measurement. World averages are found to be B( tau to e nu nu )= (17.81+or-0.06) and B( tau to mu nu nu )=(17.36+or-0.06). These results are consistent with universality in the charged current couplings to a precision of about 0.25The branching ratio measurement can also be used to constrain the "low energy parameter" eta . It is shown that the sensitivity to eta depends on details of the momentum acceptance for muon identification in the different experiments. Assuming universality in the couplings, the estimate eta =0.012+or-0.024 is obtained. (19 refs).The large samples of tau decays available from CLEO and the four LEP experiment have resulted in new, precise measurements of the leptonic branching ratios of the . The experimental techniques to obtain these results are reviewed with special emphasis on the DELPHI measurement. World averages are found to be Be = (17.81 +/- 0.06) % and Bmu = (17.36 +/- 0.06) %. These results are consistent with universality in the charged current couplings to a precision of about 0.25 %. The branching ratio measurements can also be used to constrain the "low energy parameter" eta. It is shown that the sensitivity to eta depends on details of the momentum acceptance for muon identification in the different experiments. Assuming universality in the couplings, the estimate eta = 0.012 +/- 0.024 is obtained
Search for W ' -> t(b)over-bar in the lepton plus jets final state in proton-proton collisions at a centre-of-mass energy of root s=8 TeV with the ATLAS detector
No full textA search for new charged massive gauge bosons, called W', is performed with the ATLAS detector at the LHC, in proton-proton collisions at a centre-of-mass energy of root s = 8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb(-1). This analysis searches for W' bosons in the W' -> t (b) over tilde decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W' bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W' -> t (b) over bar cross-section times branching ratio and on the W'-boson effective couplings as a function of the W'-boson mass using the CLs procedure. For a left-handed (right-handed) W' boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1016/j.physletb.2015.02.051</p
Search for new resonances decaying to a or boson and a Higgs boson in the , , and channels with collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors, 18 pages (plus author list + cover pages: 36 pages total), 13 figures, 1 table. Submitted to PLB. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2015-18/International audienceA search is presented for new resonances decaying to a or boson and a Higgs boson in the , , and channels in collisions at TeV with the ATLAS detector at the Large Hadron Collider using a total integrated luminosity of 3.2 fb. The search is conducted by looking for a localized excess in the / invariant or transverse mass distribution. No significant excess is observed, and the results are interpreted in terms of constraints on a simplified model based on a phenomenological Lagrangian of heavy vector triplets
Measurements of Cross Sections and Couplings of the Higgs Boson Using the ATLAS Detector
No full textMeasurements of cross sections and couplings of the Higgs boson using the ATLAS detector at CERN's LHC are presented. Data from proton proton collisions at 7, 8 and 13 TeV are discussed. A range of production and decay couplings can be tested with a precision that depends on the generality of the assumptions made. Data at 7 and 8 TeV are also combined with CMS results to enhance the precision.The results are all consistent with predictions of the Standard Model
Search for a CP-odd Higgs boson decaying to Zh in pp collisions at root s=8 TeV with the ATLAS detector
No full textSee paper for full list of authors – 13 pages plus author list + cover pages (30 pages total), 5 figures, 2 tables, submitted to Phys. Lett. B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2013-06/International audienceA search for a heavy, CP-odd Higgs boson, , decaying into a boson and a 125 GeV Higgs boson, , with the ATLAS detector at the LHC is presented. The search uses proton--proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb. Decays of CP-even bosons to or pairs with the boson decaying to electron or muon pairs are considered, as well as decays with the boson decaying to neutrinos. No evidence for the production of an boson in these channels is found and the 95% confidence level upper limits derived for \sigma (gg\rightarrow A) \times \mbox{BR}(A \rightarrow Zh) \times \mbox{BR}(h \rightarrow f\bar{f}) are 0.098--0.013 pb for and 0.57--0.014 pb for in a range of 220--1000 GeV. The results are combined and interpreted in the context of two-Higgs doublet models
Search for B→K^{(*)}νν̅ and Invisible Quarkonium Decays
No full textWe search for the flavor-changing neutral-current decays B→K^{(*)}νν¯, and the invisible decays J/ψ→νν̅ and ψ(2S)→νν̅ via B→K^{(*)}J/ψ and B→K^{(*)}ψ(2S), respectively, using a data sample of 471×10⁶ BB̅ pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the B mesons in the Ψ(4S)→ BB̅ decay, and search for the B→K^{(*)}νν̅ decay in the rest of the event. We observe no significant excess of signal decays over background and report branching fraction upper limits of B(B⁺→K⁺νν̅) < 3.7×10⁻⁵, B(B⁰→K⁰ νν̅) <8.1×10⁻⁵, B(B⁺→K*⁺ νν̅) < 11.6×10⁻⁵, B(B⁰→K*⁰ νν̅) < 9.3×10⁻⁵, and combined upper limits of B(B→Kνν̅) <3.2×10⁻⁵ and B(B→K*νν̅) < 7.9×10⁻⁵, all at the 90% confidence level. For the invisible quarkonium decays, we report branching fraction upper limits of B(J/ψ→νν̅) < 3.9×10⁻³ and B(ψ(2S)→νν̅) < 15.5×10⁻³ at the 90% confidence level. Using the improved kinematic resolution achieved from hadronic reconstruction, we also provide partial branching fraction limits for the B→K^{(*)}νν̅ decays over the full kinematic spectrum
Measurement of the rate of b anti-b b anti-b events in hadronic Z decays and the extraction of the gluon splitting into b anti-b
No full textThe rate was measured using about hadronic decays collected by the DELPHI experiment in 1994 and 1995. Events were forced into 3-jets with and a b-tag was required for every jet. The rate was measured to be: where the invariant mass of every system is above twice the b quark mass. Using the value of the probability of secondary production of a pair from a gluon per hadronic decay, , was extracted and found to be:
Dalitz plot analyses of B-0 -> (D-DK+)-K-0 and B+-> (D)over-bar(-)D(0)K(+) decays
No full text© 2015, APS Journal
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