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new UrQMD [message #15472]

Mon, 09 September 2013 08:43

Anna Senger
Messages: 49
Registered: April 2005
Location: GSI

continuous participant

From: *gsi.de

Hi. As you know Alla reported some problems with di-e J/psi due to new UrQMD. I checked this for di-mu J/psi. Last time I tried to produce MuCh start version for J/psi@10AGeV I can not understand, why it does not work anymore: S/B ratio = 0.02. I got early 0.8. Many thinks were changed: new more realistic STS, clustering in MuCh etc. But... I found that background is increased in new UrQMD too ! OK, it is really good to understand the problem. We need to live with that Rolling Eyes

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Re: new UrQMD [message #15503 is a reply to message #15472]

Wed, 18 September 2013 10:10

Volker Friese
Messages: 365
Registered: April 2004
Location: GSI CBM

first-grade participant

From: *gsi.de

Dear Anna,

so what you see is very similar to what Alla observes in the di-electron channel: an increase of the combinatorial background by a factor of about 4.

However, this cannot explain your S/B's going down from 0.8 to 0.02 (i.e., by a factor of 40). If that holds true, there must be an additional source of reduction, which we should understand.

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