We report measurements of charm particle production asymmetries from the Fermilab photoproduction experiment E687. An asymmetry in the rate of production of charm versus anticharm particles is expected to arise primarily from fragmentation effects. We observe statistically significant asymmetries in the photoproduction of D + , D ∗+ and D 0 mesons and find small (but statistically weak) asymmetries in the production of the D s + meson and the Λ c + baryon. Our inclusive photoproduction asymmetries are compared to predictions from nonperturbative models of charm quark fragmentation.
Production asymmetry. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Antiparticle/particle production ratio. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Production asymmetry for particles produced in association with a D*(2010)+-. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table.
The high mass μ + μ − pairs produced by 280 GeV μ + on a carbon target are studied in a search for the Y production. The high mass continuum in the region 2–18 GeV is interpreted in terms of QED pair production and of μ pairs originating from the decay of hidden and open charm particles as well as of hadrons ( π , K) from deep inelastic interactions. The upper limit for the upsilon production by muons is found to be, at the 90% confidence level, σ γ ·(γ→μ + μ − )<13·10 −39 cm 2 /nucleon.
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We have observed the production of the Ds± by a high-energy neutron beam on nuclear targets. The Ds± was observed in the decay mode Ds±→φπ±, φ→K+K−. The average of the inclusive cross sections for Ds+ and Ds− hadroproduction is measured to be BdσdxF=2.85±0.80±0.86 μb/nucleon at xF=0.175 on the assumption of a linear A dependence, where B≡Γ(Ds±→φπ±)Γ(Ds±→all).
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CHARGED PARTICLES HAVE LARGE ESCAPE ANGLE. DIFRACTIVE SCATTERED PION.
CHARGED PARTICLES HAVE LARGE ESCAPE ANGLE. DIFRACTIVE SCATTERED PION.
Coherent 3 π production on nine different nuclear targets has been studied using a 40 GeV/ c π − beam at the Serpukhov accelerator (CERN-Serpukhov experiment no. 5). The absorption in nuclear matter of the produced system has been measured, analysing the data on the different nuclear targets. Identica results are obtained from the differential cross sections and from the coherent nuclear cross sections. The 1 + waves show a very weak absorption, definitely smaller than 0 − and 2 − waves. No influence on the absorption comes from the spin-flip amplitudes, which have been found to be negligible in the coherent region.
Data are extracted from graph by JINR data group.
A sample of $1.69\times 10^7$ fully reconstructed $\pi^0\to\gamma e^+e^-$ decay candidates collected by the NA48/2 experiment at CERN in 2003--2004 is analysed to search for the dark photon ($A'$) production in the $\pi^0\to\gamma A'$ decay followed by the prompt $A'\to e^+e^-$ decay. No signal is observed, and an exclusion region in the plane of the dark photon mass $m_{A'}$ and mixing parameter $\varepsilon^2$ is established. The obtained upper limits on $\varepsilon^2$ are more stringent than the previous limits in the mass range $9~{\rm MeV}/c^2<m_{A'}<70~{\rm MeV}/c^2$. The NA48/2 sensitivity to the dark photon production in the $K^\pm\to\pi^\pm A'$ decay is also evaluated.
The obtained 90% CL upper limits (ULs) on the mixing parameter $\epsilon^2$ for each dark photon (DP) mass hypothesis tested.
The inclusive cross sections of backward proton production in π − ( K − , p ) -Be, Al, Cu, Pb interactions at 40 GeV/ c are presented. Protons have been detected in the angular range 150°–165° and kinetic energy region 0.1–0.3 GeV. The invariant cross-section ratios for various beam particles are independent of the values of kinetic energy and of the nuclear target type: 〈ƒ K − /ƒ π − 〉= 0.87 ± 0.03 stat ± 0.03 syst , 〈ƒ p /ƒ π − 〉 = 1.82 ± 0.10 stat ± 0.05 syst . The A -dependence of the cross-section slope parameter for A ⩾27 is less than ∼2%.
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Results for the Cabibbo suppressed semileptonic decays D 0 → π − e + ν and D 0 → π − μ + ν (charge conjugates are implied) are reported by Fermilab photoproduction experiment E687. We find 45.4 ± 13.3 events in the electron mode and 45.6 ± 11.8 in the muon mode. The relative branching ratio BR (D 0 →π − l + v) BR (D 0 →K − l + v) for the combined sample is measured to be 0.101 ± 0.020 (stat.) ± 0.003 (syst.) 14 .
CONST(C=V-CD and CONST(C=V-CS) are the Cabibbo-Kobayashi-Maskawa matrix elemets.
Charged hadronic four-body decays of D 0 mesons have been studied in the E687 photoproduction experiment at Fermilab. Branching ratios relative to the D 0 → K − π + π + π − decay mode for the Cabibbo-suppressed decays D 0 → π − π + π − π + , D 0 → K − K + π − π + have been measured and the first evidence of the D 0 → K − K + K − π + decay mode is reported. An analysis of the D 0 → K − K + π − π + resonance structure is also presented.
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CHARGED IS CUMULATIVE PI+-, OR K+-, OR P+-.
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