Search for single photon direct production in p + p collisions at s=53.2 GeV

doi:10.1016/0370-2693(78)90630-5

Physics Letters B

Volume 77, Issue 2, 31 July 1978, Pages 240-244

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Abstract

From measurements at the ISR of CERN with a lead glass counter matrix we establish an upper limit of 6% (at 95% C.L.) for the ratio of the directly produced photons to the produced π⁰ at 90° and $s = 53.2 GeV$ in the $p^{∗}_{T}$ region 2.3–3.7 GeV/c.

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The significance of the quark-quark scattering process (quark+quark→quark+quark+photon) for the production of large-q_T real photons is discussed in the framework of perturbative QCD. To extract the finite contribution of this process to the differential cross section dσ/dy d² q_T (hadron 1+hadron 2→photon+anything) we define the gluon distribution and the quark-to-photon fragmentation function beyond the leading approximation. The calculations are performed consistently in the dimensional regularization scheme. Our numerical estimates show the resulting finite qq→qqγ contribution to be a small (order α_s/2π) correction in comparison with the basic QCD subprocesses.
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As part of a study of large p_T phenomena in photon-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is 〈γ/all〉 = 0.074 ± 0.012 for 6 GeV/c < p_T 10 GeV/c, and 〈γ/all〉 = 0.26 ± 0.04 for p_T > 10 GeV/c, with an additional systematic uncertainty of ±0.05 for both values.
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¹: Research supported by the U.S. National Aeronautics and Space Administration and U.S. Energy Research and Development Administration.

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Search for single photon direct production in p + p collisions at s=53.2 GeV

Abstract

Nucl. Phys.

Nuovo Cimento Lett.

Nuovo Cimento Lett.

Nuovo Cimento

Phys. Rev. Lett.

Search for single photon direct production in p + p collisions at $s =53.2 GeV$