We present a measurement of the top quark pair production cross section in pp collisions at {radical}(s)=1.96 TeV using 318 pb{sup -1} of data collected with the Collider Detector at Fermilab. We ...select tt decays into the final states e{nu}+jets and {mu}{nu}+jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178 GeV/c{sup 2}, we measure a cross section of 8.7{+-}0.9(stat){sub -0.9}{sup +1.1}(syst) pb. We also report the first observation of tt with significance greater than 5{sigma} in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1{sub -1.4}{sup +1.6}(stat){sub -1.3}{sup +2.0}(syst) pb.
We present the results of a search for standard model Higgs boson production with decay to WW*, identified through the leptonic final states e{sup +}e{sup -}{nu}{nu},e{sup {+-}}{mu}{sup {+-}}{nu}{nu} ...and {mu}{sup +}{mu}{sup -}{nu}{nu}. This search uses 360 pb{sup -1} of data collected from pp collisions at {radical}(s)=1.96 TeV by the upgraded Collider Detector at Fermilab (CDF II). We observe no signal excess and set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson to WW* or any new scalar particle with similar decay products. These upper limits range from 5.5 to 3.2 pb for Higgs boson masses between 120 and 200 GeV/c{sup 2}.
We present the first precise measurement of the B{sub s}{sup 0}-B{sub s}{sup 0} oscillation frequency {delta}m{sub s}. We use 1 fb{sup -1} of data from pp collisions at {radical}(s)=1.96 TeV ...collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3600 fully reconstructed hadronic B{sub s} decays and 37 000 partially reconstructed semileptonic B{sub s} decays. We measure the probability as a function of proper decay time that the B{sub s} decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with B{sub s}{sup 0}-B{sub s}{sup 0} oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to B{sub s}{sup 0}-B{sub s}{sup 0} oscillations, we measure {delta}m{sub s}=17.31{sub -0.18}{sup +0.33}(stat){+-}0.07(syst) ps{sup -1} and determine vertical bar V{sub td}/V{sub ts} vertical bar =0.208{sub -0.002}{sup +0.001}(expt){sub -0.006}{sup +0.008}(theor)
A search for excited lepton production in e(+)e(-) collisions was performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies ranging from 189 GeV to 209 GeV, ...corresponding to an integrated luminosity of approximately 600 pb(-1). No evidence for excited lepton production was found. In searches for pair-produced excited leptons, lower mass limits were established in the range 94-103 GeV/c(2), depending on the channel and model assumptions. In searches for singly-produced excited leptons, upper limits on the parameter f/Lambda were established as a function of the mass.
The New Small Wheel electronics Iakovidis, G; Levinson, L; Afik, Y ...
arXiv (Cornell University),
05/2023
Paper, Journal Article
Odprti dostop
The increase in luminosity, and consequent higher backgrounds, of the LHC upgrades require improved rejection of fake tracks in the forward region of the ATLAS Muon Spectrometer. The New Small Wheel ...upgrade of the Muon Spectrometer aims to reduce the large background of fake triggers from track segments that are not originated from the interaction point. The New Small Wheel employs two detector technologies, the resistive strip Micromegas detectors and the "small" Thin Gap Chambers, with a total of 2.45 Million electrodes to be sensed. The two technologies require the design of a complex electronics system given that it consists of two different detector technologies and is required to provide both precision readout and a fast trigger. It will operate in a high background radiation region up to about 20 kHz/cm\(^{2}\) at the expected HL-LHC luminosity of \(\mathcal{L}\)=7.5\(\times10^{34}\)cm\(^{-2}\)s\(^{-1}\). The architecture of the system is strongly defined by the GBTx data aggregation ASIC, the newly-introduced FELIX data router and the software based data handler of the ATLAS detector. The electronics complex of this new detector was designed and developed in the last ten years and consists of multiple radiation tolerant Application Specific Integrated Circuits, multiple front-end boards, dense boards with FPGA's and purpose-built Trigger Processor boards within the ATCA standard. The New Small Wheel has been installed in 2021 and is undergoing integration within ATLAS for LHC Run 3. It should operate through the end of Run 4 (December 2032). In this manuscript, the overall design of the New Small Wheel electronics is presented.
A search for the pair production of fourth generation b'-quarks was performed using data taken by the DELPHI detector at LEP-II. The analysed data were collected at centre-of-mass energies ranging ...from 196 to 209 GeV, corresponding to an integrated luminosity of 420 pb(-1). No evidence for a signal was found. Upper limits on BR(b'-> bZ) and BR(b'-> bZ) were obtained for b' masses ranging from 96 to 103 GeV/c(2) stop. These limits, together with the theoretical branching ratios predicted by a sequential four generations model, were used to constrain the value of R-CKM=vertical bar V-cb(') /V-tb'V-tb vertical bar there V-cb', V-tb' and V-tb are elements of the extended CKM matrix.
Study of double-tagged γγ events at LEPII Abdallah et al, DELPHI Collaboration: J; Åsman, Barbro; Berntzon, Lisa ...
European physical journal. C, Particles and fields,
06/2006, Letnik:
46, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Double-tagged interactions of photons with virtualities Q2 between 10 GeV2 and 200 GeV2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated ...luminosity of 550 pb-1. The γ*γ*→μ+μ- data agree with QED predictions. The cross-section of the reaction γ*γ*→hadrons is measured and compared to the LO and NLO BFKL calculations.
Study of double-tagged gamma gamma events at LEPII Abdallah, J.; Botner, Olga; Brenner, Richard ...
The European physical journal. C, Particles and fields,
2006, Letnik:
46, Številka:
3
Journal Article
Recenzirano
Double-tagged interactions of photons with virtualities Q(2) between 10 GeV2 and 200 GeV2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated ...luminosity of 550 pb(-1). The gamma*gamma* -> mu(+)mu(-) data agree with QED predictions. The cross-section of the reaction gamma*gamma* -> hadrons is measured and compared to the LO and NLO BFKL calculations.
A search for the dimuon decay of the Standard Model (SM) Higgs boson is performed using data corresponding to an integrated luminosity of 139 fb−1 collected with the ATLAS detector in Run 2 pp ...collisions at s=13 TeV at the Large Hadron Collider. The observed (expected) significance over the background-only hypothesis for a Higgs boson with a mass of 125.09 GeV is 2.0σ (1.7σ). The observed upper limit on the cross section times branching ratio for pp→H→μμ is 2.2 times the SM prediction at 95% confidence level, while the expected limit on a H→μμ signal assuming the absence (presence) of a SM signal is 1.1 (2.0). The best-fit value of the signal strength parameter, defined as the ratio of the observed signal yield to the one expected in the SM, is μ=1.2±0.6.
The observation of Higgs boson production in association with a top quark pair (tt¯H), based on the analysis of proton–proton collision data at a centre-of-mass energy of 13 TeV recorded with the ...ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb−1, and considering Higgs boson decays into bb¯, WW⁎, τ+τ−, γγ, and ZZ⁎, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the tt¯H searches using a dataset corresponding to integrated luminosities of 4.5 fb−1 at 7 TeV and 20.3 fb−1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total tt¯H production cross section at 13 TeV is measured to be 670 ± 90 (stat.) −100+110 (syst.) fb, in agreement with the Standard Model prediction.
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