Evidence is presented that although s-channel helicity conservation is dominant in p” photoproduction, a small amount of helicity flip which is not strongly dependent on photon energy occurs for dipions 0 near the p mass. The ratio of helicity single-flip to nonflip amplitudes at the y-p vertex is comparable in magnitude to that found in q s tattering . Work supported by the U. S. Atomic Energy Commission and the National Science Foundation. ** On leave from the Weizmann Institute, Rehovoth, Israel. *** Present address: Max-Planck-Institut fiir Physik und Astrophysik, Miinchen. f Present address: University of Glasgow, Physics Dept., Glasgow, Scotland. ‘?Present address: University of Hamburg, Hamburg, Germany. tftPresent address: DESY, Hamburg, Germany. (Submitted to the XVI International Conference on High Energy Physics, Batavia, Illinois, September 6-13, 1972, and to Phys. Rev. Letters.) Photoproduction of p” mesons in the reaction yp -pop is generally considered to be diffractive, i. e., dominated by Pomeron exchange. 192y3 It has previously been shown 2y 3 that at low 1 ti the s-channel helicity of the photon is almost completely conserved by the pea This led Gilman et al. 4 -to speculate that s-channel helicity conservation (SHC) was a property of Pomeron exchange. Analysis of w elastic scattering5 and of polarization correlations6 at 6 GeV/c indicates that SHC is approximately valid for the proton vertex as well, the I=0 exchange helicity flip amplitudes being N 10% of the nonflip amplitudes at that energy. In this letter we investigate the contribution of helicity flip at the y-p vertex using new photoproduction data at 9.3 GeV. Because of background interference problems 3,7 we shall first present the experimental data on the dipion angular distributions and discuss the underlying p” amplitude structure later. The data presented here are from a 1.2 million picture exposure of the SLAC-LBL 82” hydrogen bubble chamber to a 9.3 GeV linearly polarized photon beam. This beam is produced by backscattering laser photons from the SLAC 19 GeV electron beam. For comparison we use data from exposures at 2.8 and 4.7 GeIQ2’ 3 a comprehensive description of experimental details can be found in Ref. 2, 3, and 8. In this letter we consider in detail only the angular distributions of p” decay in yp pop, although we have made a parallel analysis of the reaction yp --wp and shall include some relevant parameters of this reaction for comparison with the p”. In Fig. 1 we show the density matrix elements for dipion pairs in the p” region in the helicity system from a maximum-likelihood fit to the data in t intervals as described in Appendix A of Ref. 3. This fitting procedure removes +!incoherent A and phase-space backgrounds but assumes no coherent

A method is developed for separating ν N interactions from interactions involving an intranuclear cascade in νNe scattering at a mean neutrino energy of 145 GeV. The fraction of events featuring a cascade is evaluated by using a sample of νNe charged-current interactions. It is found that the multiplicity of charged particles in the forward direction takes the same value for events with and without a cascade for 4< W 2 <550 GeV 2 . In the backward direction, cascade events have the charge multiplicity higher than the multiplicity for cascade-free events by 2.36 units. It is found that particles with momenta less than 2 GeV/ c make a dominant contribution to the rescattering process. A depletion of the fastest particles for W 2 <50 GeV 2 is observed, in accord with the formation-time concept.

Rho photoproduction is studied at 2.8 and 4.7 GeV using a linearly polarized photon beam in a hydrogen bubble chamber. The dependence of the p” mass shape on the momentum transfer ‘is inconsistent with the Ross-Stodolsky factor. The production of n+rpairs in the s-channel C. m, helicity-conserving p-wave state accounts for almost all events in the p region. Evidence is presented for an interference of p” production with background. The data are compared with the Siiding model and total and differential cross sections for p 0 production are presented. (Submitted to Phys. Rev. Letters) * . Work supported in part by the U. S. Atomic Energy Commission and the National Science Foundation. ** *** Visitor from Laboratoire Interuniversitaire des Hautes Energies, Brussels, Belgium. f On leave from Max-Planck-Institut fiir Physik und Astrophysik, Munich, Germany. On leave from Weizmann Institute, Rehovoth, Israel. f f fff On leave from Brookhaven National Laboratory, Upton, New York. On leave from DESY, Hamburg, Germany, Previous studies of p” photoproduction in the reaction yp-p?r+?r(1) have shown that the rho shape is skewed with respect to a p-wave Breit-Wigner resulting in an apparent mass shift of the order of 40 MeV. 1,2 _ These observations have necessitated the use of models to fit the data, and because no model has been preferred experimentally, the p” production cross section has been uncertain to -20%. We present model-independent cross sections for production ._ of r’7rrpairs from reaction (1) in the s-charmel C. m. helicity-conserving p-wave state which dominates in the p region. 3 We also determined the p” production cross sections using the SSding model, 4 which was found to agree with the data. The results published here are part of a detailed study of photoproduction with a bubble chamber using a linearly polarized photon beam. We obtained 90 f 4 events/pb and 149 * 6 events/pb at 2.8 and 4.7 GeV, respectively, Measurements of the total yp cross se&ion at 1.4, 2.8 and 4.7 GeV have already been reported; 5a the analysis of the p” decay distributions and results on o and h* production are given elsewhere. 3 I. EXPERIMENTAL SETUP The 82-inch hydrogen bubble chamber at SLAC was exposed to a photon beam obtained by Compton backscattering a linearly polarized ruby laser beam on high energy electrons. By collimating both the electron and the backscattered photon beam to less than ld5 radians the width at half maximum of the photon energy spectrum is f 2.6% and i 3.3% at 2.8 and 4.7 GeV, respectively. The average degree of linear polarization as calculated for the Compton scattering process is 94% and 92%, respectively. Most of the film was taken with 70-80 photons/picture. MO& details of the beam can be found elsewhere. 5b

The cross section for bb¯ production in 800GeV/c pN interactions has been measured in Fermilab experiment E771 to be 43−17+27(stat)−7+7(syst)nb per nucleon from the observation of events in which both the b and the b¯ decay semimuonically or a B decays into a J/ψ followed by J/ψ→μ+μ−.Received 7 July 1997DOI:https://doi.org/10.1103/PhysRevLett.82.41©1999 American Physical Society

Holography has been used successfully in combination with conventional optics for the first time in a large cryogenic bubble chamber. the 15-foot bubble chamber at Fermilab, during a physics run. The innovative system combined the reference beam with the object beam, irradiating a conical volume of similar to 1.4 m(3). Bubble tracks from neutrino interactions with a width of similar to 120 mu m have been recorded with good contrast. The ratio of intensities of the object light to the reference light striking the him is called the beam branching ratio. We obtained in our experiment an exceedingly small minimum-observable ratio of (0.54 +/- 0.21) x 10(-7). The technology has the potential for a wide range of applications. (C) 1999 Elsevier Science B.V. All rights reserved.

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. Jψ, ψ′ and γ total cross sections as well as the ratio B(ψ′ → μμ)σ(ψ′)(B(Jψ → μμ)σ(Jψ)) have been measured. Results are compared with theoretical predictions and with results at other energies.

A measurement of the strong coupling constant {alpha}{sub s} using the event-shape variable y{sub 3} (the differential two-jet rate) in the reaction e{sup +}e{sup {minus}} {yields} hadrons is presented. The analysis is based on data from the TPC/Two-Gamma detector at the PEP e{sup +}e{sup {minus}} storage ring taken between 1984 and 1986 at a center-of-mass energy of E{sub cm} = 29 GeV. A value of {alpha}{sub s}(29 GeV) = 0.160 {+-} 0.012 is obtained, where the error is the quadratic sum of experimental and theoretical uncertainties. The procedure for determining {alpha}{sub s} is the same as that used by the ALEPH and TOPAZ experiments, which allows for a consistent comparison of the {alpha}{sub s} values obtained at different center-of-mass energies. The observed energy dependence {open_quotes}running{close_quotes} of {alpha}{sub s} is found to be in good agreement with the QCD prediction, and is clearly incompatible with a constant value.

We present branching fraction measurements of three-prong decays of the tau- lepton based on data from the TPC/Two-Gamma detector at SLAC PEP. The decays are classified according to the identities of the charged tracks to give simultaneous measurements of B[tau- --> nu(tau)K-pi+pi-]=0.58(-0.13)+0.15% and B[tau- --> nu(tau)K-K+pi-]=0.15+0.15(-0.07)+0.09)%, and upper limits of B[tau- --> nu(tau)pi-K+pi-]<0.25% B[tau- --> nu(tau)K-pi+K-]<0.09%, and B[tau- --> nu(tau)K-K+K-]<0.21%, where additional neutrals may be present in each case. The branching fractions are normalized to the world average three-prong topological branching fraction and there is an estimated 20% systematic error in addition to the listed statistical errors. We find the mass distributions in the K-pi+pi- decay are consistent with K1 dominance, and obtain branching fractions of B[tau- --> nu(tau)K1-(1270)]=0.41(-0.35)+0.41% and B[tau- --> nu(tau)K1-(1400)]=0.76(-0.33)+0.40%

Using data from the TPC/Two-Gamma experiment at the SLAC e+e- storage ring PEP, a C = +1 resonance has been observed in the pi+pi-pi0gamma final state resulting from the fusion on one nearly real and one quite virtual photon. The actual decay channel is probably pi+pi-pi0pi0, where one final-state photon is not detected, and the mass of the fully reconstructed state would be approximately 1525 MeV. A four-pion decay mode in turn implies that the resonance has even isospin. The nonobservation of this R (1525) when both initial-state photons are nearly real suggests a spin-1 assignment. Since the large measured value of the product of the branching ratio into pi+pi-pi0pi0 and the gammagamma coupling makes it unlikely that this state is the mostly ssBAR f1(1510), its interpretation may lie outside of conventional meson spectroscopy. There is a second, less-significant enhancement observed in the same reaction at a four-pion mass centered around 2020 MeV.

Two-photon production of the charmonium state χc has been studied by the TPC/Two-Gamma experiment at the SLAC e+e− collider PEP. We observe evidence of the χc2 state in the channel γγ→χc2, χc2→γJ/ψ, J/ψ→l+l− and obtain a value of Γγγ(χc2)=3.4±1.7±0.9 keV. This is the first observation of the two-photon production of a χc state. Comparison is made with previous experimental results and QCD predictions for Γγγ(χc2).

From an exposure of the Fermilab 15-foot bubble chamber to the Tevatron quadrupole triplet neutrino beam, we have determined the ratio of neutral-current (NC) to charged-current (CC) interactions to be 0.288 +/- 0.032 for events with visible hadron momentum above 10 GeV/c. The mean nu (nuBAR) event energy is 150 (110) GeV, which is higher than that for any previous beam. This result agrees with those from previous experiments at lower energies. The NC/CC ratio is derived for a combined sample of nu and nuBAR events. A value of 0.274 +/- 0.038 is obtained for the dominant nu-component assuming nuBAR NC/CC = 0.39 +/- 0.08. For events with visible hadron momentum above 25 GeV/c, where the neutral hadron contamination remaining in the NC sample is assumed to be negligible, the combined NC/CC is 0.323 +/- 0.025 and the K0 production rates are 0.375 +/- 0.064 per CC and 0.322 +/- 0.073 per NC event. The corresponding LAMBDA-rates are 0.161 +/- 0.030 per CC and 0.113 +/- 0.030 per NC event. The K0 and LAMBDA-distributions of the fractional hadron energy variable z in NC events are consistent with those in CC events.

-Two-photon production of the charmonium state xc has been studied by the TPC/Two-Gamma experiment at the SLAC e+e-collider PEP. We observe evidence of the xc2 state in the channel yy + ~~2, xc2 +-yJ/$, J/T/I + l+l-and obtain a value of lYrr(xc2) = 3.4 f 1.7 f 0.9 keV. This is the first observation of the two-photon production of a xc state. Comparison is made with previous experimental results and QCD predictions for Prr(xc2). The two-photon decay widths, F- ,-,, of the C = +l charmonium states such as the xc2 provide valuable information in understanding the nature of heavy .-. quarkonia. In potential models, the xc2 is assumed to be a CC bound state, 3P2 in spectroscopic notation. Predictions for Prr have been made in relativistic potential- .-models[ " " and in dispersion-relation models based upon QCD sum rules!' These calculations lead to a rather wide range of values 0.4 < Frr(xc2) c 2.0 keV. A precise experimental measurement of rrr(Xc2) would set a constraint on these models. Furthermore, since the ratio of partial widths into two gluons and into two photons, rgg(xc2)lWxc2), is related to the strong coupling constant clef*] the experimental determination of this ratio offers a method to test the validity of perturbative QCD predictions. Experimental measurements of two-photon decay widths for charmonium states are difficult due to their lack of dominant decay modes. The two-photon decay of the xc2 state has been directly observed in production from radiative $' decayi5' B " ' and in pp annihilation. Since the decay branching rat,e to two photons is small, about O.l%, these results have large uncertainties. Two-photon reactions at eSe-colliders provide another method for measuring rrr. The TPC/Two-Gamma' " ] and CLEO'glcollaborations have used four-hadron final states, such as 7rITs7rlT-rsr~ and K+K-n+r-, to search for the ~~2, but the substantial background from the continuum makes observing the expected few signal events difficult, and only upper limits on Fyy(xc2) have been obtained. The VENUS Collaboration " " has reported a search for the two-photon production of xc2 in the decay channel xc2-+-yJ/$, J/T) '-t Z+l-, where I is either an 3 electron or a muon. Again, only an upper limit on l?yy(xcz) has been reported. The overall decay branching ratio to the sum of two lepton flavors, (1.65 f 0.15)%~ " ' is. .. comparable to each of the four-hadron decays mentioned above, and has a smaller 1-uncertainty. …

E771 is a Fermilab fixed target open geometry high acceptance spectrometer experiment to study production of beauty states in 0.8 TeV proton‐nucleus interactions, and beauty decay particularly to final states containing a J/Ψ (detected via its decay to μ+μ−). The spectrometer consists of a silicon microstrip vertex detector (final configuration, 24 planes; x, y, u, v; of 25 and 50 micron pitch), upstream of which are beam‐defining planes of silicon microstrip detectors and target foils of various materials and thicknesses; the SVD is followed by tracking planes of drift‐ and proportional‐wire‐chambers, a momentum‐analysing bending magnet, further planes of DC’s, PWC’s and pad chambers, a γ‐ and electron‐detecting lead glass wall, and finally several meters of iron interspersed with muon‐detecting resistive pad chambers and scintillators. Progress is reviewed in building, installing and tuning the equipment for the next Fermilab fixed target run beginning in mid‐1991, and expected to continue for 5 months. An extensive data run is anticipated for the 1993–4 fixed target period. In the 1991 run several dozen fully‐ reconstructed B to J/Ψ to μ=μ− events should be obtained per month of good running at an interaction rate of 2 MHz. For future runs the goal is to operate at 10 MHz and to reconstruct several thousand B decays per year to measure B decay branching ratios, study B0B̄0 mixing, and search for CP violation effects.