0000000000347165
AUTHOR
H. D. Yoo
Search for Stopped Gluinos frompp¯Collisions ats=1.96 TeV
Long-lived, heavy particles are predicted in a number of models beyond the standard model of particle physics. We present the first direct search for such particles' decays, occurring up to 100 h after their production and not synchronized with an accelerator bunch crossing. We apply the analysis to the gluino (g), predicted in split supersymmetry, which after hadronization can become charged and lose enough momentum through ionization to come to rest in dense particle detectors. Approximately 410 pb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector during Run II of the Fermilab Tevatron collider are analyzed in search of such "stopped gluinos" decaying in…
Measurement of theΛbLifetime in the Exclusive DecayΛb→J/ψΛ
We have measured the {lambda}{sub b} lifetime using the exclusive decay {lambda}{sub b}{yields}J/{psi}{lambda}, based on 1.2 fb{sup -1} of data collected with the D0 detector during 2002-2006. From 171 reconstructed {lambda}{sub b} decays, where the J/{psi} and {lambda} are identified via the decays J/{psi}{yields}{mu}{sup +}{mu}{sup -} and {lambda}{yields}p{pi}, we measured the {lambda}{sub b} lifetime to be {tau}({lambda}{sub b})=1.218{sub -0.115}{sup +0.130}(stat){+-}0.042(syst) ps. We also measured the B{sup 0} lifetime in the decay B{sup 0}{yields}J/{psi}({mu}{sup +}{mu}{sup -})K{sub S}{sup 0}({pi}{sup +}{pi}{sup -}) to be {tau}(B{sup 0})=1.501{sub -0.074}{sup +0.078}(stat){+-}0.050(sy…
Measurement of the Semileptonic Branching Ratio ofBs0to an Orbitally ExcitedDs**State:Br(Bs0→Ds1−(2536)μ+νX)
In a data sample of approximately 1.3 fb-1 collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D* K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely from B0_s, an extraction of the semileptonic branching ratio Br(B0_s -> D_s1(2536) mu nu X) is made.
Combination of CDF and D0 measurements of the W boson helicity in top quark decays
Aaltonen, T. et al.
Search for Charged Higgs Bosons Decaying into Top and Bottom Quarks in pp Collisions
Made available in DSpace on 2022-04-28T20:54:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-14 We describe a search for production of a charged Higgs boson, qq̄′→H+, reconstructed in the tb̄ final state in the mass range 180≤MH+≤300GeV. The search was undertaken at the Fermilab Tevatron collider with a center-of-mass energy s=1.96TeV and uses 0.9fb-1 of data collected with the D0 detector. We find no evidence for charged Higgs boson production and set upper limits on the production cross section in the types I, II, and III two-Higgs-doublet models (2HDMs). An excluded region in the (MH+, tanβ) plane for type I 2HDM is presented. © 2009 The American Physical Society. Universida…
Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVusing soft electronb-tagging
The authors present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318 pb{sup -1} of data collected with the CDF II detector, they measure the t{bar t} production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9{sub -1.0}{sup +1.0}(stat.){sub -1.0}{sup +1.1}(syst.) pb. The cross section value assumes a top quark mass of m{sub t} is presented in the paper. This result is cons…
Search for flavor-changing-neutral-current D meson decays
We study the flavor-changing-neutral-current process c to u mu+ mu- using 1.3 fb^-1 of p p bar collisions at sqrt(s) = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the Ds+ and D+ to phi pi+ to mu+ mu- pi+ final states with significance greater than four standard deviations above background for the D+ state. We search for the continuum decay of D+ to pi+mu+mu- in the dimuon invariant mass spectrum away from the phi resonance. We see no evidence of signal above background and set a limit of B(D+ to pi+mu+mu-) < 3.9 x 10^-6 at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c to u mu+ mu- t…
Model-independent measurement of the W-boson helicity in top-quark decays at D0.
Made available in DSpace on 2022-04-28T20:37:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-14 Science and Technology Facilities Council We present the first model-independent measurement of the helicity of W bosons produced in top quark decays, based on a 1fb-1 sample of candidate tt̄ events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron pp̄ Collider. We reconstruct the angle θ* between the momenta of the down-type fermion and the top quark in the W boson rest frame for each top quark decay. A fit of the resulting cos θ* distribution finds that the fraction of longitudinal W bosons f0=0.425±0.166(stat)±0.102(syst) and the f…
Experimental Discrimination between Charge2e/3Top Quark and Charge4e/3Exotic Quark Production Scenarios
We present the first experimental discrimination between the 2e/3 and 4e/3 top quark electric charge scenarios, using top quark pairs (ttbar) produced in ppbar collisions at sqrt{s}=1.96 TeV by the Fermilab Tevatron collider. We use 370 pb-1 of data collected by the D0 experiment and select events with at least one high transverse momentum electron or muon, high transverse energy imbalance, and four or more jets. We discriminate between b- and bbar-quark jets by using the charge and momenta of tracks within the jet cones. The data is consistent with the expected electric charge, |q|=2e/3. We exclude, at the 92% C.L., that the sample is solely due to the production of exotic quark pairs QQba…
Properties ofL=1B1andB2*Mesons
This Letter presents the first strong evidence for the resolution of the excited B mesons B-1 and B-2(*) as two separate states in fully reconstructed decays to B+(*())pi(-). The mass of B-1 is measured to be 5720.6 +/- 2.4 +/- 1.4 MeV/c(2) and the mass difference Delta M between B-2* and B-1 is 26.2 +/- 3.1 +/- 0: 9 MeV/c(2), giving the mass of the B-2* as 5746.8 +/- 2.4 +/- 1.7 MeV/c(2). The production rate for B-1 and B-2* mesons is determined to be a fraction (13.9 +/- 1.9 +/- 3.2)% of the production rate of the B+ meson.