We report the observation of a narrow charmoniumlike state produced in the exclusive decay process B+/--->K+/-pi(+)pi(-)J/psi. This state, which decays into pi(+)pi(-)J/psi, has a mass of ...3872.0+/-0.6(stat)+/-0.5(syst) MeV, a value that is very near the M(D0)+M(D(*0)) mass threshold. The results are based on an analysis of 152M B-Bmacr; events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The signal has a statistical significance that is in excess of 10sigma.
We present a measurement of the standard model CP violation parameter sin2 phi(1) based on a 29.1 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB ...asymmetric-energy e(+)e(-) collider. One neutral B meson is fully reconstructed as a J/psi K(S), psi(2S)K(S), chi(c1)K(S), eta(c)K(S), J/psi K(L), or J/psi K(*0) decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin2 phi(1) = 0.99+/-0.14(stat)+/-0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.
The muon detector of the HERA-B experiment at DESY (Hamburg, Germany) is a gaseous detector that provides muon identification in a high-rate environment. Pairs of muons with an invariant mass in the ...region of the J//spl psi/, meson ensure the first-level trigger for the experiment. Three different types of gas proportional chambers are employed: tube, pad, and pixel. The muon detector is fully installed and has been continuously running since November 1999. A clear signal for J//spl psi//spl rarr//spl mu//spl mu/, is reconstructed from data taken during the commissioning run. Design of the muon system as well as experience gained with detector commissioning are presented in this paper. The severe radiation environment of the HERA-B experiment leads to a maximum charge deposit on a wire, within the muon detector, of 200 mC/cm per year. We report recent results of aging studies performed by irradiating proportional wire chambers filled with Ar/CF/sub 4/,/CK and Ar/CF/sub 4//CO/sub 2/ mixtures under various conditions. These results show that aging rates obtained by irradiating a small region of the wire with a radioactive source cannot be extrapolated to the irradiation of large areas in an environment of hadronic interactions. Our experience shows that the aging rate depends not only on the total collected charge but also on the mode of operation and area of irradiation.
A simple gas pixel chamber Balagura, V; Belyaev, I; Chistov, R ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/1996, Letnik:
379, Številka:
3
Journal Article
Recenzirano
We present a new design of a wire gas detector referred to as the gas pixel chamber. Several prototypes with cell sizes of 10 × 10, 8 × 8 and 6 × 6 mm
2 have been built and successfully tested at ...ITEP, Moscow. These chambers are capable of working at very high intensities, higher than 10
5 particles/cm
2/s, with an efficiency above 99% and with a drift time less of than 80 ns even for the largest cell size of 10 × 10 mm
2. The chamber can be built with a thickness of less than 1% of a radiation length. Gas pixel chambers are proposed to be used in the inner parts of the muon system and the high-
p
t trigger system of the HERA-B experiment at DESY.
The lifetimes of the B(0) and B- mesons are extracted from 29.1 fb(-1) of data collected with the Belle detector at the KEK B factory. A fit to the decay length differences of neutral and charged B ...meson pairs, measured in events where one of the B mesons is fully reconstructed in several hadronic modes, yields tau(B(0)) = 1.554+/-0.030(stat)+/-0.019(syst) ps, tau(B-) = 1.695+/-0.026(stat)+/-0.015(syst) ps, and tau(B-)/tau(B(0)) = 1.091+/-0.023(stat)+/-0.014(syst).
Observation of B+-->psi(3770)K Chistov, R; Abe, K; Akatsu, M ...
Physical review letters,
07/2004, Letnik:
93, Številka:
5
Journal Article
Recenzirano
We report the first observation of the decay B+-->psi(3770)K+ where the psi(3770) is reconstructed in the D0(-)D(0) and D+D- decay channels. The obtained branching fraction is ...B(B+-->psi(3770)K+)=(0.48+/-0.11+/-0.07)x10(-3). We have measured the branching fraction for the decay B+-->D0(-)D0K+ to be (1.17+/-0.21+/-0.15)x10(-3) and set a 90% confidence level upper limit of 0.90 x 10(-3) for the decay B+-->D+D-K+. We also present the results of a search for possible decays to D(-)D and D0(-)D(0)pi(0) of the recently observed X(3872) particle. The analysis is based on 88 fb(-1) of data collected at the Upsilon(4S) resonance by the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.
We report the first measurement of the branching fraction for the inclusive decay B-->X(s)l(+)l(-), where l is either an electron or a muon, and X(s) is a hadronic recoil system that contains an s ...quark. We analyzed a data sample of 65.4 x 10(6) B meson pairs collected with the Belle detector at the KEKB e(+)e(-) asymmetric-energy collider. We find B(B-->X(s)l(+)l(-))=6.1 +/-1.4(stat) +1.4-1.1(syst) x 10(-6) for dilepton masses greater than 0.2 GeV/c(2).
Using the HERA-B detector, the b (b) over bar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b (b) over bar production was tagged via ...inclusive bottom quark decays into J/psi by exploiting the longitudinal separation of J/psi --> l(+)l(-) decay vertices from the primary proton-nucleus interaction. Both e(+)e(-) and mu(+)mu(-) channels have been reconstructed and the combined analysis yields the cross section sigma(b (b) over bar) = 32(-12)(+14)(stat) (+6)(-7)(sys) nb/nucleon.
The radiative decay B-->phi K gamma is observed for the first time. The branching fraction for the charged B--->phi K- gamma decay mode is measured to be B(B--->phi K- ...gamma)=(3.4+/-0.9+/-0.4)x10(-6). The photon energy distribution for the B--->phi K- gamma decay is presented. The signal for the neutral B(0)-->phi K(0)gamma decay mode is not statistically significant and an upper limit, B(B(0)-->phi K(0)gamma)<8.3x10(-6) at 90% C.L., is set. The analysis is based on a data set of 90 fb(-1) collected by the Belle experiment at the e(+)e(-) asymmetric collider KEKB.
PDF
