180 research outputs found
Search for the Cryptoexotic Member of the Baryon Antidecuplet 1/2+ in the Reactions pi- p --> pi- p and pi- p --> K L
The main goal of this proposal is the search for a narrow cryptoexotic
nucleon resonance by scanning of the pi- p system invariant mass in the region
(1610-1770) MeV with the detection of pi- p and K Lambda decays. The scan is
supposed to be done by the variation of the incident pi- momentum and its
measurement with the accuracy of up to +-0.1% (better than 1 MeV in terms of
the invariant mass in the whole energy range) with a set of proportional
chambers located in the first focus of the magnetooptical channel. High
sensitivity of the method to the resonance under search is shown. The secondary
particles scattered from a liquid hydrogen target are detected by sets of the
wire drift chambers equipped with modern electronics. The time scale of the
project is about 3 years. The budget estimate including manpower, the apparatus
and operation cost, is about 40 million rubles. The beam time required is (4-6)
two week runs on "high" (10 GeV/c) flattop of the ITEP proton synchrotron.Comment: 16 pages, 10 figures. v2: an acknowledge adde
A high-pressure hydrogen time projection chamber for the MuCap experiment
The MuCap experiment at the Paul Scherrer Institute performed a
high-precision measurement of the rate of the basic electroweak process of
nuclear muon capture by the proton, . The
experimental approach was based on the use of a time projection chamber (TPC)
that operated in pure hydrogen gas at a pressure of 10 bar and functioned as an
active muon stopping target. The TPC detected the tracks of individual muon
arrivals in three dimensions, while the trajectories of outgoing decay (Michel)
electrons were measured by two surrounding wire chambers and a plastic
scintillation hodoscope. The muon and electron detectors together enabled a
precise measurement of the atom's lifetime, from which the nuclear muon
capture rate was deduced. The TPC was also used to monitor the purity of the
hydrogen gas by detecting the nuclear recoils that follow muon capture by
elemental impurities. This paper describes the TPC design and performance in
detail.Comment: 15 pages, 13 figures, to be submitted to Eur. Phys. J. A; clarified
section 3.1.2 and made minor stylistic corrections for Eur. Phys. J. A
requirement
First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+
We report the first observation of a charm-strange meson DsJ(2632) at a mass
of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production
experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and
D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a
significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a
corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9
MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2
at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta)
is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its
decay pattern is also unusual, being dominated by the Ds eta decay mode.Comment: 5 pages, 3 included eps figures. v2 as accepted for publication by
PR
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