# WA70 experiment

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The WA70 calorimeter viewed from downstream of the beam line.  Photo by R.W. Poultney 1986

The **WA70 experiment** was a collaboration between the Universities of [Geneva](/source/University_of_Geneva), [Glasgow](/source/University_of_Glasgow), [Liverpool](/source/University_of_Liverpool), [Milan](/source/University_of_Milan) and [Neuchatel](/source/University_of_Neuch%C3%A2tel) using the facilities of the OMEGA spectrometer at [CERN](/source/CERN).[1]

The purpose of the experiment was to study [direct photons](/source/Direct_photons) produced in [proton](/source/Proton)-[proton](/source/Proton) and [proton](/source/Proton)-[pion](/source/Pion) collisions within a fixed target of [liquid hydrogen](/source/Liquid_hydrogen) at the [CERN SPS](/source/Super_Proton_Synchrotron).[2] The experiment was proposed on 6 August 1980 [2] and formally approved on 22 October 1981.[3] Preliminary data was taken in 1983 with physics runs in 1984, 1985 and 1986.[4]

A novel feature of the experiment was a liquid scintillator [calorimeter](/source/Calorimeter_(particle_physics)),[5] which was built in quadrants and designed to measure the energy of [direct photons](/source/Direct_photons) and other particles produced by the collisions. This was situated downstream of the [liquid hydrogen](/source/Liquid_hydrogen) target.

Results were presented at scientific conferences and published in scientific journals.[6] The measured [cross section](/source/Cross_section_(physics)) for direct photon production was in agreement with predictions from perturbative [QCD](/source/Quantum_chromodynamics).[7]

The spokesperson for the experiment was Professor Michel Martin,[2] and participants included Dr. [Fabiola Gianotti](/source/Fabiola_Gianotti)[8] (who went on to become [CERN](/source/CERN)'s first woman [Director General](/source/List_of_Directors_General_of_CERN)).

## References

1. **[^](#cite_ref-BonvinBopp1989_1-0)** Bonvin, E.; Bopp, R.; Carroll, L. J.; Cass, A. J.; Chung, S. U.; Donnat, M.; Dorsaz, P. A.; Feliks, M. E.; Fluri, L.; Jackson, J. N.; Kienzle-Focacci, M. N.; Lynch, J. G.; Martin, M.; Mathys, L.; Negus, P. J.; Perini, L.; Poultney, R.; Range, W. H.; Rosselet, L.; Snow, S. W.; Thompson, A. S.; Turnbull, R. M.; Werlen, M. (1989). ["Double prompt photon production at high transverse momentum byπ − on protons at 280 GeV/c"](https://cds.cern.ch/record/191522). *Zeitschrift für Physik C*. **41** (4): 591–598. [doi](/source/Doi_(identifier)):[10.1007/BF01564702](https://doi.org/10.1007%2FBF01564702). [ISSN](/source/ISSN_(identifier)) [0170-9739](https://search.worldcat.org/issn/0170-9739). [S2CID](/source/S2CID_(identifier)) [119370172](https://api.semanticscholar.org/CorpusID:119370172).

1. ^ [***a***](#cite_ref-proposal_2-0) [***b***](#cite_ref-proposal_2-1) [***c***](#cite_ref-proposal_2-2) Bachmann, L. (6 August 1980). [Proposal to the SPSC : study of direct photon events in hadronic collisions](https://cds.cern.ch/record/601279/files/cm-p00045423.pdf) (PDF) (Report). CERN. CERN-SPSC-80-61; SPSC-P-147. Retrieved 28 January 2020.

1. **[^](#cite_ref-3)** [Decision of the 54th Meeting of the Research Board held on 22 October 1981](https://cds.cern.ch/record/1014193/files/CM-P00060196.pdf) (PDF) (Report). CERN. 23 October 1981. CERN-DG-RB-81-21. Retrieved 28 January 2020.

1. **[^](#cite_ref-4)** ["WA70/OMEGA/DIRPHOTON : Study of Direct Photon Events in Hadronic Collisions"](https://greybook.cern.ch/greybook/experiment/detail?id=WA70). *The CERN Experimental Programme*. CERN. Retrieved 28 January 2020.

1. **[^](#cite_ref-5)** Bonesini, M.; et al. (1987). "A Lead-Liquid Scintillator Electromagnetic Calorimeter for Direct Photon Physics". *Nuclear Instruments and Methods*. **A261** (3): 471–480. [Bibcode](/source/Bibcode_(identifier)):[1987NIMPA.261..471B](https://ui.adsabs.harvard.edu/abs/1987NIMPA.261..471B). [doi](/source/Doi_(identifier)):[10.1016/0168-9002(87)90356-1](https://doi.org/10.1016%2F0168-9002%2887%2990356-1).

1. **[^](#cite_ref-6)** ["List of WA70 publications recorded by CERN"](https://cds.cern.ch/search?ln=en&cc=CERN+Published+Articles&p=experiment%3Awa70&action_search=Search&op1=a&m1=a&p1=&f1=&c=CERN+Published+Articles&c=&sf=&so=a&rm=&rg=50&sc=1&of=hb). *CERN Document Server (CDS)*. CERN. Retrieved 28 January 2020.

1. **[^](#cite_ref-Martin1988_7-0)** Martin, Michel (1988). "Direct Photon Production by π-p, π+p and pp Interaction at 280 GeV/c: Results from the WA70 Experiment at CERN". *QCD Hard Hadronic Processes*. NATO ASI Series. Vol. 197. pp. 113–124. [doi](/source/Doi_(identifier)):[10.1007/978-1-4684-8842-5_9](https://doi.org/10.1007%2F978-1-4684-8842-5_9). [ISBN](/source/ISBN_(identifier)) [978-1-4684-8844-9](https://en.wikipedia.org/wiki/Special:BookSources/978-1-4684-8844-9). [ISSN](/source/ISSN_(identifier)) [0258-1221](https://search.worldcat.org/issn/0258-1221).

1. **[^](#cite_ref-8)** ["Recorded WA70 publications with Fabiola Gianotti as author"](http://inspirehep.net/search?ln=en&p=find+au+Gianotti+and+exp+CERN-WA-070&of=hb&action_search=Search&sf=earliestdate&so=d). *INSPIRE-HEP*. Retrieved 28 January 2020.

## External links

- [CERN-WA-070 experiment record](https://inspirehep.net/experiments/1109441) on [INSPIRE-HEP](/source/INSPIRE-HEP)

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