A study of charged charm production is made at 400 GeV incident energy of protons in nuclear emulsion. A total of 7005 primary stars have been scrutinized to look for charm particle decays in the forward cone within a decay distance of 100–1,000 μm (3,056 stars) and 100–2,000 μm (3,949 stars). In all 10 charm candidates decaying to 3 charged particles plus neutrals have been observed. Background due to secondary interactions for events of such topology is estimated to be ≈3. Background due to strange particle decays is estimated to be negligible. The rest of the events are attributed toΛc+ andD± decays. This leads to a value of 91±35 μb/nucleon for the total charged charm production cross section. Using production cross section forD± from other experiments we obtainΛc+ production cross section as 62±27 μb/nucleon. Two cases of pair production of charm have been seen.
Axis error includes +- 0.0/0.0 contribution (NOT GIVENDECAY-BR(BRN=D+ --> 3CHARGED (NEUTRALS), BR=0.5)//DECAY-BR(BRN=D- --> 3CHARGED (NEUTRALS), BR=0.5)//DECAY-BR(BRN=LAMBDA/C+ --> 3CHARGED (NEUTRALS), BR=0.6)).
Axis error includes +- 0.0/0.0 contribution (NOT GIVENDECAY-BR(BRN=D+ --> 3CHARGED (NEUTRALS), BR=0.5)//DECAY-BR(BRN=D- --> 3CHARGED (NEUTRALS), BR=0.5)//DECAY-BR(BRN=LAMBDA/C+ --> 3CHARGED (NEUTRALS), BR=0.6)).
Narrow states observable through the emission of monoenergetic charged pions have been searched for in p p annihilation at rest in a gaseous hydrogen target where annihilation from atomic angular momentum L = 1 states dominates. No structure is observed. The 5σ upper limit for the production of narrow states in the mass range 1100–1670 MeV is 2 × 10 −3 of all annihilations.
X means a narrow state.
2550 interactions of 12 C in emulsion at 4.5 A GeV / c have been used to study the properties of projectile fragments. The multiplicity and projected angular distributions of projectile fragments in different target groups have been studied. The production cross section of the reaction in which projectile 12 C breaks up into two Z = 3 fragments is found to be 6.6 × 10 −3 of the total inelastic cross section. The projected angular distributions of fragments exhibit features of limiting fragmentation. Statistically significant azimuthal correlations among fragments in the azimuthal plane indicates that the fragmenting nucleus gets a transverse momentum during the collision.
No description provided.
NUCLEUS IS CNO.
NUCLEUS IS AGBR.
A detailed study of the mechanism of emission of pions and protons in the forward and backward hemispheres in 4.5A GeV/c silicon-emulsion interactions has been carried out. For this purpose, a random sample comprising 1024 interactions caused by silicon nuclei is analyzed to examine the behavior of the emission characteristics of pions and protons emitted in the forward and backward hemispheres. The values of the forward-backward ratio and the asymmetry parameter as a function of the number of heavily ionizing particles are determined. The behavior of the angular distributions of pions and protons in the backward hemisphere and multiplicity correlations is also investigated. The results yield quite interesting information regarding the mechanism of production of pions and protons in the backward hemisphere.
No description provided.
We report on the first measurement of the spin-dependent structure function g 1 d of the deuteron in the deep inelastic scattering of polarised muons off polarised deuterons, in the kinematical range 0.006< x <0.6, 1 GeV 2 < Q 2 <30 GeV 2 . The first moment, Γ 1 d =ʃ 0 1 g 1 d d x=0.023±0.020 ( stat. ) ± 0.015 ( syst. ) , is smaller than the prediction of the Ellis-Jaffe sum rules. Using earlier measurements of g 1 p , we infer the first moment of the spin-dependent neutron structure function g 1 n . The difference Γ 1 p − Γ 1 n =0.20±0.05 (stat.) ± 0.04 (syst.) agrees with the prediction of the Bjorken sum rule, Γ 1 p − Γ 1 n =0.191±0.002.
Virtual photon asymmetry A1.
Spin-dependent structure function G1.
The dijet invariant mass distribution has been measured in the region between 140 and 1000 GeV/c2, in 1.8 TeV p p¯ collisions. Data collected with the Collider Detector at Fermilab show agreement with QCD calculations. A limit on quark compositeness of Λc>1.3 TeV is obtained. Axigluons with masses between 240 and 640 GeV/c2 are excluded at 95% C.L. if we assume ten open decay channels. Model-independent limits on the production of heavy particles decaying into two jets are also presented.
No description provided.
If quarks are composite particles then excited states are expected. We have searched in pp¯ collisions for excited quarks (q*) which decay to common quarks by emitting a W boson (q*→qW) or a photon (q*→qγ). The simplest model of excited quarks has been excluded for mass M*<540 GeV/c2 at 95% confidence level.
No description provided.
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We present the results of a search for the top quark in 19.3 pb−1 of p¯p collisions at √s =1.8 TeV. The data were collected at the Fermilab Tevatron collider using the Collider Detector at Fermilab (CDF). The search includes standard model tt¯ decays to final states eeνν¯, eμνν¯, and μμνν¯ as well as e+ν+jets or μ+ν+jets. In the (e,μ)+ν+jets channel we search for b quarks from t decays via secondary vertex identification and via semileptonic decays of the b and cascade c quarks. In the dilepton final states we find two events with a background of 0.56−0.13+0.25 events. In the e,μ+ν+jets channel with a b identified via a secondary vertex, we find six events with a background of 2.3±0.3. With a b identified via a semileptonic decay, we find seven events with a background of 3.1±0.3. The secondary vertex and semileptonic-decay samples have three events in common. The probability that the observed yield is consistent with the background is estimated to be 0.26%. The statistics are too limited to firmly establish the existence of the top quark; however, a natural interpretation of the excess is that it is due to tt¯ production. We present several cross-checks. Some support this hypothesis; others do not. Under the assumption that the excess yield over background is due to tt¯, constrained fitting on a subset of the events yields a mass of 174±10−12+13 GeV/c2 for the top quark. The tt¯ cross section, using this top quark mass to compute the acceptance, is measured to be 13.9−4.8+6.1 pb.
Cross section refers to top quark mass equals 174 +- 10 +13 - 12 GeV. Two events in the dilepton final states and six events in the electron or muon nu jets final states.
Experimental data on multiplicities and correlations of charged particles of different types produced in collisions of 4.5 A GeV/c carbon-12 with emulsion are reported and discussed. The data are compared with the results of other experiments on nucleus–nucleus and hadron–nucleus collisions. It is found that the particle production mechanism in nucleus–nucleus collisions is almost the same as in hadron–nucleus collisions. It is also observed that the shower particles' multiplicity distributions obey a KNO type scaling law, which supports the aforementioned result.
No description provided.
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We present an analysis of data from p p¯ collisions at a center-of-mass energy of √s =1800 GeV. A measurement is made of the ratio R≡σB(p p¯→W→eν)/σB(p p¯→Z0→ee). The data represent 19.6 pg−1 collected by the Collider Detector at Fermilab during the 1992–1993 collider run of the Fermilab Tevatron. We find R=10.90±0.32(stat)±0.29(syst), and from this value we extract a measurement of the W→eν branching ratio Γ(W→eν)/Γ(W)=0.1094±0.0033(stat)±0.0031(syst). From this branching ratio we set a limit on the top quark mass of mt>62 GeV/c2 at the 95% confidence level. In contrast with direct searches for the top quark, this limit makes no assumptions about the allowed decay modes of the top quark. In addition, we use a calculation of the leptonic width Γ(W→eν) to obtain a value for the W total decay width: Γ(W)=2.064±0.060(stat)±0.059(syst) GeV.
The cross section ratio contains the branching ratio of W --> E NU and Z0 --> E+ E-. RE = PBAR P --> W+ X.