HEPData Search

Showing 8 of 18 results

Threshold structure of the quasifree p + n --> d + eta reaction.

Calen, H. ; Dyring, J. ; Fransson, K. ; et al.

Phys.Rev.Lett. 80 (1998) 2069-2072, 1998.

Inspire Record 468434 DOI 10.17182/hepdata.19524

The quasifree p+n→d+η reaction cross section has been measured at the threshold using 1295 MeV protons in the CELSIUS storage ring and an internal cluster-jet deuterium target. The kinematics is chosen such that the target proton can be assumed to be a spectator. The Fermi momentum of the target neutron is used to extract the energy dependence of the cross section by reconstructing the kinematics on an event-by-event basis. The data cover excess energies from threshold to 10 MeV in the center of mass of the final dη system. Approaching the threshold the cross section is enhanced compared to what is expected from phase space. This behavior is typical for a strong final-state interaction.

1 data table

Table 1

Cross section as a function of the C.M. excess energy.

Two-body neutral final states produced in anti-proton - proton annihilations at 2.911-GeV <= s**(1/2) <= 3.686-GeV

The Fermilab E760 collaboration Armstrong, T.A. ; Bettoni, D. ; Bharadwaj, V. ; et al.

Phys.Rev.D 56 (1997) 2509-2531, 1997.

Inspire Record 444897 DOI 10.17182/hepdata.22300

We have performed an experiment in the Antiproton Accumulator at Fermilab to study two-body neutral final states formed in p¯p annihilations. Differential cross sections are determined in the center-of-mass energy range 2.911<s<3.686 GeV for the final states π0π0, ηπ0, ηη, π0γ, and γγ. The energy dependence of differential cross sections at 90° in the center of mass is studied to test the predictions of phenomenological QCD scaling hypotheses which predict power-law dependence.

43 data tables

Table 1

No description provided.

Table 2

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Table 3

No description provided.

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Forward - backward charge asymmetry of electron pairs above the Z0 pole

The CDF collaboration Abe, F. ; Akimoto, H. ; Akopian, A. ; et al.

Phys.Rev.Lett. 77 (1996) 2616-2621, 1996.

Inspire Record 417098 DOI 10.17182/hepdata.50121

We present a measurement of the forward-backward charge asymmetry of the process pp¯→Z0/γ+X,Z0/γ→e+e− at Mee>MZ, using 110pb−1 of data at s=1.8TeV collected at the Collider Detector at Fermilab. The measured charge asymmetries are 0.43±0.10 in the invariant mass region Mee>105GeV/c2, and 0.070±0.016 in the region 75<Mee<105GeV/c2. These results are consistent with the standard model values of 0.528±0.009 and 0.052±0.002, respectively.

1 data table

Table 1

The forward-backward asymmetry resuts from angular differential cross section : D(SIG)/D(COS(THETA*) = A*(1 + COS(THETA*)**2) + B*COS(THETA*), where THETA * is the emission angle of the E- relative to the quark momentum in the rest frame of the E+ E- pair.

Measurements of the proton elastic form-factors for 1-GeV/c2 <= Q2 <= 3-GeV/C**2 at SLAC

Walker, R.C. ; Filippone, B. ; Jourdan, J. ; et al.

Phys.Rev.D 49 (1994) 5671-5689, 1994.

Inspire Record 360764 DOI 10.17182/hepdata.22469

We report measurements of the proton form factors GEp and GMp extracted from elastic scattering in the range 1≤Q2≤3 (GeV/c)2 with total uncertainties < 15% in GEp and < 3% in GMp. Comparisons are made to theoretical models, including those based on perturbative QCD, vector-meson dominance, QCD sum rules, and diquark constituents in the proton. The results for GEp are somewhat larger than indicated by most theoretical parametrizations, and the ratios of the Pauli and Dirac form factors Q2(F2pF1p) are lower in value and demonstrate a weaker Q2 dependence than those predictions. A global extraction of the elastic form factors from several experiments in the range 0.1 0.1<Q2<10 (GeV/c)2 is also presented.

6 data tables

Table 1

Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.

Table 2

Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.

Table 3

Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.

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Measurement of the proton electromagnetic form-factors in the timelike region at 8.9-GeV2 - 13-GeV2

The E760 collaboration Armstrong, T.A. ; Bettoni, D. ; Bharadwaj, V. ; et al.

Phys.Rev.Lett. 70 (1993) 1212-1215, 1993.

Inspire Record 340584 DOI 10.17182/hepdata.19781

Cross sections for the reaction pp¯→e+e− have been measured at s=8.9,12.4, and 13.0 GeV2. The cross sections have been analyzed to obtain the proton electromagnetic form factors in the timelike region. We find that GM(q2)∝q−4αs2(q2) for q2≥5 (GeV/c)2.

5 data tables

Table 1

No description provided.

Table 2

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Table 3

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Upper Limits of the Proton Magnetic Form-factor in the Timelike Region From $\bar{p} p \to e^+ e^-$ at the {CERN} {ISR}

The Annecy(LAPP)-CERN-Genoa-Lyon-Oslo-Rome-Strasbourg-Turin collaboration Baglin, C. ; Baird, S. ; Bassompierre, G. ; et al.

Phys.Lett.B 163 (1985) 400-403, 1985.

Inspire Record 218159 DOI 10.17182/hepdata.49639

From the measurement of e + e - pairs from the reaction p̄p→e + e - at the CERN-ISR, using an antiproton beam and a hydrogen jet target, we derived upper limits for the proton magnetic form factor in the time-like region at Q 2 ⋍8.9( GeV c ) 2 and Q 2 ⋍12.5( GeV c ) 2 .

1 data table

Table 1

No description provided.

Limit on the B ---> u Coupling from Semileptonic B Decay

The CLEO collaboration Chen, A. ; Goldberg, M. ; Horwitz, N. ; et al.

Phys.Rev.Lett. 52 (1984) 1084, 1984.

Inspire Record 199380 DOI 10.17182/hepdata.20474

We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.

2 data tables

Table 1

No description provided.

Table 2

No description provided.