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R Verdier

Publications and source records attributed to R Verdier.

10 recordsLinked to original sources
PubMed2000

First direct measurement of the parity-violating coupling of the Z0 to the s quark

We present the first direct measurement of A(s), the parity-violating coupling of the Z0 boson to the strange quark, using approximately 550 000 e(+)e(-)-->Z0-->hadrons events recorded by the SLC Large Detector with a polarized e(-) beam. We tagged Z0-->s&smacr; events by the absence of B or D hadrons and the presence in each hemisphere of a high momentum K+/- or K(0)(s). Fitting the polar angle distributions of the strangeness-signed thrust axis gave A(s) = 0.895+/-0.066(stat)+/-0.062(syst). The analyzing power and uu+d&dmacr; background were constrained using the data, greatly reducing any model dependence.

Journal Article↗
PubMed2000

Charged-particle multiplicity near midrapidity in central Au+Au collisions at sqrt[SNN]=56 and 130 GeV.

We present the first measurement of pseudorapidity densities of primary charged particles near midrapidity in Au+Au collisions at sqrt[s(NN)] = 56 and 130 GeV. For the most central collisions, we find the charged-particle pseudorapidity density to be dN/deta|(|eta|<1) = 408+/-12(stat)+/-30(syst) at 56 GeV and 555+/-12(stat)+/-35(syst) at 130 GeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.

Journal Article↗
PubMed2000

Precise measurement of the b-quark fragmentation function in Z0 boson decays

We have developed a new technique for inclusive reconstruction of the energy of B hadrons. The excellent efficiency and resolution of this technique allow us to make the most precise determination of the b-quark fragmentation function, using e(+)e(-)-->Z0 decays recorded in the SLAC Large Detector experiment. We compared our measurement with the predictions of a number of fragmentation models. We excluded several of these models and measured the average scaled energy of weakly decaying B hadrons to be = 0.714+/-0. 005(stat)+/-0.007(syst)+/-0.002 (model dependence).

Journal Article↗
PubMed1997

Study of eight cases of cancer in 426 rheumatoid arthritis patients treated with methotrexate.

OBJECTIVE: To report cancer cases in 426 rheumatoid arthritis patients treated with methotrexate, and determine whether there was an increased incidence of cancer compared with patients never treated with methotrexate (rheumatoid controls) and to the whole regional population. METHODS: The duration of methotrexate treatment was 37.4 (SD 27.9) months. This population was compared with 420 rheumatoid arthritis controls and with a regional population of 812,344 people. Life table analysis was performed to compare the cancer incidence in the two rheumatoid populations. Adjustment for potentially confounding factors was done. The indirect standardisation methods was used to compare each rheumatoid population with the regional population. RESULTS: Eight cases of cancer (1.88%; 4.04 cases/1000 person years) were diagnosed in the methotrexate population v six (1.43%; 58.8 cases/1000 person years) in the rheumatoid controls. The life table method showed a higher incidence of cancer in the rheumatoid controls (P = 0.0001). In a multivariate analysis (Cox model), the only significant factor explaining this difference in the cancer incidence was age (P = 0.02). In the regional population there were 6418 new cases of cancer (0.79%; 2.85 cases/1000 person years). By the indirect standardisation method, the ratio of observed cases to expected cases of cancer in each of the rheumatoid populations was not significantly different from 1. CONCLUSIONS: In these eight cases, methotrexate was not found to be responsible for generating cancers. However, because of data regarding lymphomas and methotrexate, and because of the short follow up, especially in the control group, longer prospective studies are warranted.

Adult↗
PubMed1987

Cryptosporidiosis in Haitian children.

We used a modified acid-fast stain to detect Cryptosporidium oocysts in unconcentrated stools from 824 Haitian children less than 2 years of age with acute diarrhea. Oocysts were identified in stools from 17.5% of 291 children seen at a rural dispensary and in 16.3% of stools from 533 children in an urban hospital. Children with cryptosporidiosis were identified throughout a 22-month period from October 1982 to July 1984, without seasonal predilection. Cryptosporidiosis was twice as common in infants greater than 6 months of age than in younger infants. Cryptosporidium oocysts were rarely found in stools of infants receiving only breast milk. The clinical presentation of children with cryptosporidiosis was similar to other patients with diarrhea who did not have cryptosporidiosis. No asymptomatic Cryptosporidium infections were detected among 71 family members of 31 children with cryptosporidiosis. Three of the 71 family members less than 3 years of age were found to have diarrhea and Cryptosporidium oocysts. In follow-up studies of 31 patients, oocysts persisted in stools for a mean of 14 days (range 5-31 days). Duration of oocyst excretion was directly correlated with duration of diarrhea. These findings suggest that Cryptosporidium is an important cause of acute self-limited diarrheal illness to Haitian children.

Breast Feeding↗