Soft photon production in 450 GeV/cp-Be collisions

Antos̆, J.; Beker, H.; Brons, S.; Bussmann, Klaus; Dagan, S.; Drees, A.; C, Erd; Esten, M.J.; Fabjan, C.; Glässel, P.; Goerlach, U.; Hedberg, V.; Lissauer, D.; Mazzoni, M. A.; McCubbin, N. A.; Neubert, Matthias; Nevski, P.; Olsen, L.; Pfeiffer, A.; Ray, Anne E.; Schukraft, J.; Shapira, D.; Soltani, J.; Specht, H. J.; Stumer, I.; Thompson, J.; Veenhof, R.; Willis, W.; Woody, C. L.

doi:10.1007/bf01562546

Cited by 27 publications

(32 citation statements)

References 14 publications

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“…In addition, the yield seemed to increase approximately as the square of the associated hadron multiplicity, which would have signified a collective production mechanism [12]. These findings were not confirmed by a more extensive later experiment [9] by some members of the same group.…”

Section: Introductionmentioning

confidence: 81%

“…For data which provide absolute normalization, the procedure is straightforward. They are those listed in the Introduction except for the AFS [3] and Antoš et al [9] experiments. In paper [3], the AFS Collaboration presented the p T -spectrum of photons observed in pp collisions at √ s = 63 GeV (their Fig.…”

Section: Comparison Of Models To Datamentioning

confidence: 99%

“…The inclusive production of soft photons in particle collisions at high energies has been studied in several experiments [1][2][3][4][5][6][7][8][9] using various experimental techniques.…”

Section: Introductionmentioning

confidence: 99%

“…Antoš et al [9] used a modified setup of the HELIOS experiment [6] and measured the inclusive p T spectra of soft photons produced at central and slightly backward rapidities in 450 GeV/c p-Be collisions. Two independent photon measurement methods with corresponding detectors and analysis chains were used in parallel: (i) a combination of gas chambers, converter plates and a BGO matrix for the conversion method; (ii) a BaF 2 array for the time of flight photon identification method.…”

Section: Introductionmentioning

confidence: 99%

“…Two independent photon measurement methods with corresponding detectors and analysis chains were used in parallel: (i) a combination of gas chambers, converter plates and a BGO matrix for the conversion method; (ii) a BaF 2 array for the time of flight photon identification method. The authors of [9] observed a significant excess of direct photons at very low p T (< 15 MeV/c) above the background from hadronic decays. This excess was consistent with the expected contribution from hadronic bremsstrahlung, calculated from the classical electrodynamics formula [10].…”

Section: Introductionmentioning

confidence: 99%

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Consistency of data on soft photon production in hadronic interactions

Lichard

1994

Phys. Rev. D

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The glob model of Lichard and Van Hove and the modified soft annihilation model (MSAM) of Lichard and Thompson are used as a phenomenological tool for relating results from various experiments on soft photon production in high energy collisions. The total phenomenological expectation is composed of contributions from classical bremsstrahlung, the soft annihilation model and the glob model. The empirical excess above the background from hadronic decays at very small longitudinal momenta of photons is well reproduced, as well as that for transverse momenta p T > ∼ 10 MeV/c. Some data do not require the glob model and MSAM components in the phenomenological mixture, but do not exclude them. On the basis of consistency of all data with the total theoretical expectation we argue that the results of all experiments are mutually consistent. The models are unable to describe the excess of ultrasoft photons (p T < ∼ 10 MeV/c), seen by some, but not all, experiments. This may indicate an as yet unknown projectile-mass-dependent production mechanism. Possible relations of soft photon production to other phenomena are discussed. A simple-to-use, but physically equivalent version of the glob model is developed, which enables an easy check of presented results.

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Section: Introductionmentioning

confidence: 81%

Section: Comparison Of Models To Datamentioning

confidence: 99%

“…The inclusive production of soft photons in particle collisions at high energies has been studied in several experiments [1][2][3][4][5][6][7][8][9] using various experimental techniques.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Consistency of data on soft photon production in hadronic interactions

Lichard

1994

Phys. Rev. D

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Soft photons in hadron-hadron collisions: synchrotron radiation from the QCD vacuum?

Botz¹,

Haberl²,

Nachtmann³

1995

Z. Phys. C - Particles and Fields

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We discuss the production of soft photons in high energy hadron-hadron collisions. We present a model where quarks and antiquarks in the hadrons emit "synchrotron light" when being deflected by the chromomagnetic fields of the QCD vacuum, which we assume to have a nonperturbative structure. This gives a source of prompt soft photons with frequencies ω ∼ < 300 MeV in the c.m. system of the collision in addition to hadronic bremsstrahlung. In comparing the frequency spectrum and rate of "synchrotron" photons to experimental results we find some supporting evidence for their existence. We make an exclusive-inclusive connection argument to deduce from the "synchrotron" effect a behaviour of the neutron electric formfactor G n E (Q 2 ) proportional to (Q 2 ) 1/6 for Q 2 ∼ < 20 fm −2 . We find this to be consistent with available data. In our view, soft photon production in high energy hadron-hadron and leptonhadron collisions as well as the behaviour of electromagnetic hadron formfactors for low Q 2 are thus sensitive probes of the nonperturbative structure of the QCD vacuum.

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Spin correlations in the Drell–Yan process, parton entanglement, and other unconventional QCD effects

Nachtmann

2014

Annals of Physics

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We review ideas on the structure of the QCD vacuum which had served as motivation for the discussion of various non-standard QCD effects in high-energy reactions in articles from 1984 to 1995. These effects include, in particular, transverse-momentum and spin correlations in the Drell-Yan process and soft photon production in hadron-hadron collisions. We discuss the relation of the approach introduced in the above-mentioned articles to the approach, developed later, using transverse-momentum-dependent parton distributions (TDMs). The latter approach is a special case of our more general one which allows for parton entanglement in high-energy reactions. We discuss signatures of parton entanglement in the Drell-Yan reaction. Also for Higgs-boson production in pp collisions via gluon-gluon annihilation effects of entanglement of the two gluons are discussed and are found to be potentially important. These effects can be looked for in the current LHC experiments. In our opinion studying parton-entanglement effects in high-energy reactions is, on the one hand, very worthwhile by itself and, on the other hand, it allows to perform quantitative tests of standard factorisation assumptions. Clearly, the experimental observation of parton-entanglement effects in the Drell-Yan reaction and/or in Higgs-boson production would have a great impact on our understanding how QCD works in high-energy collisions.

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Soft photon production in 450 GeV/cp-Be collisions

Cited by 27 publications

References 14 publications

Consistency of data on soft photon production in hadronic interactions

Consistency of data on soft photon production in hadronic interactions

Soft photons in hadron-hadron collisions: synchrotron radiation from the QCD vacuum?

Spin correlations in the Drell–Yan process, parton entanglement, and other unconventional QCD effects

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