G. Smadja

A search for B and ϱ′(1250) production in the reaction γp → pπ+π− + neutrals at 2.8, 4.7 and 9.3 GeV☆

Abstract We have studied the reaction γ p → p π + π − + neutrals in the LBL-SLAC 82″ hydrogen bubble chamber exposed to a linearly polarized photon beam at 2.8., 4.7 and 9.3. GeV. We observe an enhancement at 1.24 GeV in the mesonic mass recoiling against the proton. The enhancement is produced peripherally with slopes of 5−7 GeV −2 and cross sections of 1−3 μb. We show that ωπ o is likely to be the major decay mode and give upper limits for other decay modes. The enhancement can be either the J P = 1 + B meson, a yet unestablished J P = 1 − meson decaying via ωπ o , or a diffractively produced Deck-type background. The observed decay correlations are compatible with an s -channel helicity conserving production process. Our data at higher masses are consistent with a ϱϵ decay of the ϱ′(1600) and we obtain an upper limit of 4±1 μ b for ϱ′(1600) production in the final state p π + π − + neutrals at 9.3 GeV.

Inclusive ϱ0 production in γp interactions at 2.8, 4.7, and 9.3 GeV☆

Abstract Inclusive ϱ 0 production in γ p → ϱ 0 + anything is studied at 2.8, 4.7, and 9.3 GeV, using the SLAC linearly polarized backscattered laser photon beam and the 82 inch hydrogen bubble chamber. Over this energy range the inclusive inelastic ϱ 0 cross section rises from 6.0 μb to 20.5 μb. The multiplicity, i.e. the average number of μ 0 mesons per inelastic hadronic event, has an energy dependence consistent with 1n s . The inclusive cross section is studied as a function of Feynman x , c.m. rapidity, and p T 2 variables, and is also broken down into exclusive channels. At 9.3 GeV a forward inelastic peak is observed in the x distribution, containing mainly polarized ϱ 0 mesons. The cross section for this inealastic diffractive component is 2.7 ± 0.6 μ b. The p T 2 distributions are exponential with a slope of 3 − 4 (GeV/ c ) −2 , similar to that found in inclusive ϱ 0 production in pp and μ p reactions.

Observation of a four-pion vector-meson state of mass ≈ 1.5 GeV produced by linearly polarized 9.3 GeV photons

Abstract From a study of γp → 2 π + 2 π − p using 9.3 GeV linearly polarized photons, evidence is found for a J P = 1 − , I G = 1 + four pion enhancement of mass ∼ 1.5 GeV with a production cross section of 1.6 ± 0.4 μb .

OBSERVATION OF A FOUR PION VECTOR - MESON STATE OF MASS approximately equal to 1.5-GeV PRODUCED BY LINEARLY POLARIZED 9.3-GeV PHOTONS

Abstract From a study of γp → 2 π + 2 π − p using 9.3 GeV linearly polarized photons, evidence is found for a J P = 1 − , I G = 1 + four pion enhancement of mass ∼ 1.5 GeV with a production cross section of 1.6 ± 0.4 μb .