I am forwarding the following message from Michael Murray on physics measurements during this first run period. Flemming Videbaek Physics Department Brookhaven National Laboratory tlf: 631-344-4106 fax: 631-344-1334 videbaek@bnl.gov ----- Original Message ----- From: Michael Murray Tel 409 845 1411,FAX 1899, Home 823 3386 To: VIDEBAEK@hi2 Sent: Saturday, July 08, 2000 3:07 PM Subject: NUCLEAR_PHYSICS.BRAHMS Dear Jens Jorgen and Flemming, it seems that for the foreseeable future we will be limited to 1-2 collisions/second with a spread in Z of sigma=75cm and with useful beam for maybe 12 hours/day. Given this limitation I suggest that as a first physics goal we try to study nuclear EM disociation. This could best be done by selectiing collisions with |Z|<15cm and using the Beam Beam counters and a COMPLETE hexagon of tiles. Since we have such a low interaction rate we would take all events. Offline we would study the forward neutron spectrum for those events that produced nothing in the beam-beam and the tiles. While this is not a complete 4pi veto of charged particles it would cover Eta=0 to 2.2 and 3.2 to 4.3 on both sides. Using collisions away from z=0 it would be possible to extend this range for at one hemisphere. As a bi-product of such a run we would get events with a range of multiplicities in each tile. The very low multiplicity events could server as a calibration for the tiles. The calibration technique could be checked for those tiles that covered the mid-rapidity TPCs. Once this calibration is finished we could publish dN/dEta vs Eta and centrality. Steve told me that it would be simple to remove drop the tiles out of the acceptance of the spectrometers onece this run is over. I would guess that we could do this measurement in 2 days. Please could you distribute this message. Currently I am blocked from using the BRHAMS messaage servers. Yours Michael
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