M. Jenkins

Measurement of J / psi, psi-prime and upsilon total cross-sections in 800-GeV/c p - Si interactions

Abstract We report on the analysis of Charmonium and Bottomium states produced in p-Si interactions at s =38.7 GeV . The data have been collected with the open geometry spectrometer of the E771 Experiment at the FNAL High Intensity Lab. J ψ , ψ′ and γ total cross sections as well as the ratio B(ψ′ → μμ)σ(ψ′) (B( J ψ → μμ)σ( J ψ )) have been measured. Results are compared with theoretical predictions and with results at other energies.

A combination drift chamber/pad chamber for very high readout rates

Details of the construction of high-rate, mid-sized (1-m*2-m) pad chambers, intended for use in Fermi National Accelerator Laboratory (FNAL) experiment E-771, are described. Each gas volume module represents a chamber doublet: two identical anode wire planes, two transverse strip planes, and two pad planes. Wire signals, from 8-mm square cells, are recorded via TDCs; corresponding stripe and pad image signals are latched. Pad sizes range from 0.8 cm*3.6 cm to 3.2 cm*35 cm. In addition to facilitating pattern recognition, pad signals are also used as inputs to an online, high transverse momentum trigger processor.<<ETX>>

Search for direct CP violation in Λ and Ξ hyperon decays

A sensitive search for direct CP violation in Ξ− (Ξ+) and Λ (Λ) decays is underway at FNAL. Experiment E871 (HyperCP) intends to perform a precision measurement of the angular distribution of protons (anti-protons) with respect to the helicity axis in the rest frame of the Λ (Λ). The slopes of these distributions give the decay parameters αΞαΛ and αΞαΛ. An asymmetry parameter A in terms of these decay parameters has been defined for which a non-zero value would be unambiguous evidence for direct CP violation. Theoretical predictions for A range from no asymmetry up to ∼ 10−3. HyperCP expects to measure A with an uncertainty of ∼ 2 × 10−4.

HyperCP (E871) experiment at Fermilab: search for direct CP violation in hyperon decays

Abstract The Fermilab HyperCP experiment has accumulated the worlds largest sample of Ξ− and Ξ + hyperon decays within two running periods in 1997 and 1999. The primary goal of the experiment is to search for direct CP violation in the decay sequences Ξ− → Λ π− → p π− π− and Ξ + → Λ π+ → p π+ π+. A violation of CP would manifest itself as a difference between the angular distribution of the proton and the antiproton in the Λ and Λ helicity frame. The amount of data is enough to reach a statistical sensitivity of 1.4 × 10−4 in the CP violating asymmetry A ΞΛ = (αΞ αΛ − α Ξ α Λ )/(αΞ αΛ + α Ξ α Λ ). We present an analysis method used to take into account the slight differences in the production of the Ξ− and Ξ + samples. A preliminary results on A ΞΛ at the level of a few 10−3 and based on a few percent of the 1997 data will be presented.

CP violation in strange baryon decays: A report from Fermilab experiment 871

Fermilab experiment 871, HyperCP, is a search for direct CP violation in Ⅺ and Λ hyperon decays. A non-zero value in the asymmetry parameter A, defined in terms of the decay parameter products αⅪαΛ and αⅪαΛ, would be unambiguous evidence for direct CP violation. The first data-taking run finished at the end of 1997 and accumulated over one billion Ⅺ− and Ⅺ+ decays. A sensitivity in A of ≈10−4 is expected. A review of CP violation in hyperon decays is given, the HyperCP detector is described, and the status of the data analysis is discussed.

The Fermilab E771 spectrometer: A large aperture spectrometer to study charm and beauty states as detected by decays into muons

This paper describes the final incarnation of the Fermilab High Intensity Lab spectrometer which operated for ten years in the Proton West Area of Fermilab in the execution of two experiments (E537 and E705) which studied hadroproduction of high mass dimuon pairs. The version of the spectrometer used in E771 differed from earlier versions of the spectrometer by the addition of a silicon microstrip detector, pad chambers and resistive plate counters. These additions were implemented to give the spectrometer the capability of detection of secondary decay vertices from B → μ or B → Jψ → μμ decays. As discussed, the spectrometer in a short data taking period was able to address many kinds of physics, other than beauty decays.

Search for CP violation in hyperon decays

Abstract Direct CP violation in nonleptonic hyperon decays can be established by comparing the decays of hyperons and anti-hyperons. For Ξ decay to Λπ followed by Λ to pπ, the proton distribution in the rest frame of Lambda is governed by the product of the decay parameters αΞαΛ. The asymmetry ΛΞΛ, proportional to the difference of αΞαΛ of the hyperon and anti-hyperon decays, vanishes if CP is conserved. We report on an analysis of a fraction of 1997 and 1999 data collected by the HyperCP (E871) collaboration during the fixed-target runs at Fermilab. The preliminary measurement of the assymmetry is AΞΛ = [−7±12(stat)±6.2(sys)] × 10−4, an order of magnitude better than the present limit.

CP Violation in Hyperon and Charged Kaon Decays

The primary purpose of the HyperCP experiment at Fermilab is to test CP in hyperon decays by comparing the decay distributions for Ⅺ− (“cascade”) decays in the decay sequence: Ⅺ− → π− + Λ0, Λ0 → π− + p, with those for the antiparticle Ⅺ+. In addition, we can test CP in charged kaon decays by comparing the slopes of the Dalitz plot for Κ+ and Κ− decays. We are also looking at rare decay modes of charged kaons and hyperons, particularly those involving muons. In two runs in 1997 and 1999, we collected approx. 500 millon charged kaon decays, 2.5 billion Ⅺ− and Ⅺ+ decays, and 19 million Ω− and Ω+ decays. This is the largest sample of fully reconstructed particle decays ever collected.

Hadroproduction of theχ1andχ2states of charmonium in 800-GeV/cproton-silicon interactions

The cross sections for the hadroproduction of the Chi1 and Chi2 states of charmonium in proton-silicon collisions at sqrt{s}=38.8 GeV have been measured in Fermilab fixed target Experiment 771. The Chi states were observed via their radiative decay to J/psi+gamma, where the photon converted to e+e- in the material of the spectrometer. The measured values for the Chi1 and Chi2 cross sections for x_F>0 are 263+-69(stat)+-32(syst) and 498+-143(stat)+-67(syst) nb per nucleon respectively. The resulting sigma(Chi1}/sigma(Chi2) ratio of 0.53+-0.20(stat)+-0.07(syst), although somewhat larger than most theoretical expectations, can be accomodated by the latest theoretical estimates.

B physics at FNAL E771

Abstract The short-term prospects for Fermilab experiment E771 - devoted to the hadroproduction of beauty - are described as well as the major characteristics of the spectrometer. Expectations for detection and reconstruction of exclusive B decay channels are discussed.