Message 3/4053 From Sharon@FSU Mar 21, 97 08:14:07 am -0500 Resent-Message-Id: <9703211312.AA28602@nscpmail.physics.umd.edu> Resent-Date: Fri, 21 Mar 1997 08:12:16 EST Resent-From: Resent-To: Date: Fri, 21 Mar 1997 8:14:07 -0500 (EST) To: "FNALD0::LANDSBERG"@FSHEWC.HEP.FSU.EDU, ENO@UMDHEP.UMD.EDU, HOBBS@FNAL.GOV Subject: Boos on choice of Q2 scale for pair prod. of LQ From: SMTP%"boos@ifh.de" 21-MAR-1997 07:18 To: HAGOPIAN CC: Subj: Q**2 scale = MLQ? (fwd) X-Authentication-Warning: hpl3zeu1.ifh.de: boos owned process doing -bs Date: Fri, 21 Mar 1997 13:17:02 +0100 (MET) From: Edward Boos To: hagopian@fshewc.hep.fsu.edu Subject: Q**2 scale = MLQ? (fwd) Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hi Scharon, We have to check and discuss that. I hadn't any contacts with Bluemlien these days, may be he is somewhere around the world. I am in Darmstadt University at the moment as a visitor professor. Well. The statement of Mangano is also a bit strange. The natural scale, seems, should at least not smaller than 4*M_LQ^2 which is the reaction threshold. We have the only one s-channel diagram. In fact most of the cross section comes from the integration around the threshold region. And that is why it is rather strange to expect a large difference between 4*M_LQ^2 and s-hat scales. ((We will check that). The scale just 1*M_LQ^2 looks very strange because it is far away from the main for the reaction physical region. And in fact there is a big difference with s-quark pair production because in case of s-quark production in the q,q-bar subreaction there is one more t-channel diagram with the t-channel gluino exchange. And the existence of t-channel diagram could make conclusions about the loop contribution completely different. In the case of LQ for q,bar-q we have only one s-channel diagram. In some sence before any correct NLO calculations for the LQ pair production the limit from D0 is a bit conservative but correct. In the opposite way the D0 prediction would be based on not a correct callculations but on some analogy with s-quarks which in fact strictly speaking doesn't work. So let we will think and discuss. Cheers, Edward Subject: theorists, theorist, theorist... To: wanggl@fnald0.fnal.gov, hagopian@fnald0.fnal.gov, hobbs@fnald0.fnal.gov, weerts@fnald0.fnal.gov, mont@fnald0.fnal.gov, hedin@fnald0.fnal.gov, norman@fnald0.fnal.gov, bantly@fnald0.fnal.gov, dclaes@unlhep.unl.edu, pgrannis@fnald0.fnal.gov, wyatt@fnald0.fnal.gov, blessing@fnald0.fnal.gov, landsberg@fnald0.fnal.gov, gwatts@fnald0.fnal.gov, cutts@fnald0.fnal.gov, flattum@fnald0.fnal.gov, sirotenko@fnald0.fnal.gov, murphy@fnald0.fnal.gov Date: Thu, 20 Mar 1997 16:05:48 -0500 (EST) Hi Gang, I called Michelangelo, and he told me that we are using the wrong scale. he says from squarks are very similar to leptoquarks. for squarks, NLO calculations have been done. they find for scale = s-hat, the kfactor is 2, while for scale = M(LQ) the k factor is only 10-15%. he says he has called Blumlein, and Blumlein agrees now, and will put out a new version of his paper with these new cross sections. This means, when this new version comes out, out limit will go up again! I told Michelangelo that we would not change until we see some discussion in writing of this. he said that Blumlein is indeed planning on doing this. He said he will keep us informed. man oh man... michelangelo's paper is hep-ph 9703276 cheers, Sarah Forwarded message: > From MLM@vxcern.cern.ch Thu Mar 20 15:53:04 1997 > Date: Thu, 20 Mar 1997 21:52:58 +0100 (CET) > From: Michelangelo MANGANO > To: ENO@nscpmail.physics.umd.edu > Cc: MLM@vxcern.cern.ch > Message-Id: <970320215258.21032cbe@vxcern.cern.ch> > Subject: lq x-sect > > > hello sarah, I saw a note you forwarded to herbie and > bluemlein. I don't understand the statement that the x-section > at 200 gev changed from 0.16 to 0.11. The cross section for a > 200gev scalar LQ at the tevatron IS 0.16pb (in fact, it is a bit higher, > 0.18pb). You get 0.1-0.11 if you use the scale mu2=shat. The right scale, > however, is of the order of mlq (this being the lq mass), and for this scale > the cross section (as you can se from our paper) is 0.18 pb. In any > case, this mass limits should come with a detailed explanation of the > parameters used in the cross section estimate, otherwise they are not > very useful ! > > I am at fnal for a coule of days, in case you want to discuss > this more. My phone is 3466 > > bests, mlm >