From: Dieter Rohrich (dieter@fi.uib.no)
Date: Wed Aug 27 2003 - 13:48:29 EDT
Dear colleagues, some comments on the RBUP. I would like to second Flemming's arguments. Our main focus should be high-pt spectra of identified particles and flow. Both observables depend on initial temperature and volume which we think we can control be varying beam energy and the collision system. Since with lowering the beam energy our probe (parton jet) disappears, I would give central collisions of a lighter system highest priority (of course only after having collected sufficient statistics in (semi)-central AuAu at 200 GeV). Peripheral AuAu collisions behave differently from central FeFe or SiSi and the geometry is much less well defined. With best wishes, Dieter On Mon, 25 Aug 2003, Flemming Videbaek wrote: > Hi > > some additional thoughts on RBUP - and it would be useful to get comments from other interested parties. > Afterall the plan has to be complted by the end of this week. > > In the mean time the RBUP will be corrected with several suggestons received, as well as having added > information on transverse asymmetry measurements for pp. Too I will continue to make an (internal list) for > proposed measurement to get the needed integrated luminosity better understood for 200 GeV AuAu. > One point which does need some work from the people interested is to make a real estimate how much Luminosity (not weeks) is needed to do a coalesnce measurement at high y . What rapidities can one get both deuterons and protons (not from same angle > field settings) with well defined goal of yield. > > > Certainly the trust of the 200 GeV running is high-pt and flow. (where for the latter we cannot go as high as one would really like for identified particle). The order of the priority should certainly reflect this, in particulr to measure at a place where dn/dy is roughly half of that of y~0 to reflect the change in energy density. > > > The physics addressed in the two cases is of course different. > - with a light projectile (Fe is actually more and more my own choice) one essentailly change only one parameter namely > the transverse size of the system, while the energy densities are (likely) similar, thus a reduction in high-pt yield can check this important change. > > - At low energy one will attempt to see the disappereance of high-pt suppression. From a physics point this is another > change in behaviour that can help in the understanding of partonic matter. > > So why do I prioritize (prefer) one over the other in terms of run period This basically comes to to feasibility. > Initially I also thought as JJ, but now I do not beliveve we can make a measurement above pt ~2 GeV/c (two) particular since one do need the peripheral settings to construc RCP. At pt=3 the pion yield in pp is down by ~ factor 5 and at 4 by factor 12- at the same time the luminosity is down by at least a factor of 3, and possibly by another factor of 2-3 due to the limitation in the apertures of the triplets. To put this more into perspective I have put several plots on my pii3 web-page that shows the quality of spectra d2n/dptdy (not invariant spectra) in count for specific amount of luminosity. > http://pii3.brahms.bnl.gov/~videbaek/run4/index.html > > Thus for a run period of say 5 weeks at 63 GeV we can get one reasonable spectrum of at 40 deg, and basically > one measurements at one angle/field setting with FS. So one question to answer is e.g. How important is a high y > measurement at low energy - does not y~0 (or 1) settle the issue? Too, both Star and Phenix can in about 1-day make a > measurement equivalent to our that would take 4-6 weeks, and we would have almost no other physics result at high rapidity. I still think it should be attempted, the question is when; If the coming run goes very well i.e. we get what we need > at 200 GeV, from an operational point of view you certainly would not go to another specie. A new specie clearly is for > another run period. > > On the other hand with a lighter projectile (Si, Fe) one can in the same amount time get spending ~ 2-3 weeks on high-pt > several setteings and two charge states say at two rapidities, and in remaining time measure complete distributuons of > soft physics. > > > Lastly on the observation of dn/dy of pions. I agree, one do not really need to say the pions are gaussian; They are though surprisingly close , I understand they can be described by both shifted double Gaussians as well as other parametrizations that > gives a small flat region near y~0. - in any case the <RMS> of the pion-distributions from AGS to RHIC are very close to the Landau picture e.g as discussed by Carruthers. The main point I real wanted to make was the surpise these distributions have been to many, and that we can measure these well. > > > > regards > Flemming > > ------------------------------------------------------ > Flemming Videbaek > Physics Department > Brookhaven National Laboratory > > tlf: 631-344-4106 > fax 631-344-1334 > e-mail: videbaek@bnl.gov > > ----- Original Message ----- > From: Jens Jørgen Gaardhøje > To: brahms-l@bnl.gov > Cc: gardhoje@nbi.dk > Sent: Saturday, August 23, 2003 8:00 AM > Subject: Re: Beam Use Proposal > > > Dear Flemming et al. > > A few first quick comments to the document(RBUP). > > 1) I disagree with the strong statement about Gaussian meson rap. dist. Looking at Djamels data fits with a Wood Saxon type functional is just as good. In fact the chi-squaresd is probably better. At the same time the avergage pt and the appa. T seem to be flat at |y|<1.5. I would not make a strong conclusive statement, but point out that this is what we would like to understand better. I don't think we are at the end of that story. > > 2) I feel quite strongly that our main thrust in the Au+Au runs should be to focus on the new interesting signals, e.g high pt at various rapidities, and our unique possibility to study this with identiffies particles. Related issues are the CGC search. Consequently we need long Au+Au runs at max energy for these low cross section items. > Most of the other physics can be done in a short time if we have high luminosity. Not to say that they should not be done, primarily the highest rapidities, but they should not shape the program. > > 3) I disagree with the priority given to lighter ion species over lower energy. I think it is of paramount importance > to establish the systematics of high pt. suppression. sqrt(s)=56 or better 63 is not a bad choice. > I fail to fully appreciate the significance of smaller systems as opposed to more peripheral Au+Au collisions. There may be some small second order differences, but I personally doubt that there is any major physics issue hidden there. > I propose that our request for RUN IV is AU+AU max energy and Au+Au at lower energy for (1/4?) of the time IF the preceeding full energy run has proceeded well with adequate integrated lum. The request for RUN V should include studies of p+p for the reference for high pt studies at fwd. rap, and of the pol p+p at fwd rap. > I suggest that we also include some Au+Au (possibly one could put in the lighter ion runs there) > > > Well, thats my two pennys worth. Opinions? > > > cheers > JJ > > PS: it struck me that RBUP could also be Beam Use RHIC Proposal...... > ____________________________________________________________ > Jens Jørgen Gaardhøje, Assoc. Prof., Dr. Sc. > Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark. > Tlf: (+45) 35 32 53 09, secr. (+45) 35 32 52 09, Fax: (+45) 35 32 50 16. > UNESCO Natl. Comm., secr. (+45) 33 92 52 16. > Email: gardhoje@nbi.dk. > ____________________________________________________________ > > > ----- Original Message ----- > From: Flemming Videbaek > To: brahms-l@bnl.gov > Sent: Friday, August 22, 2003 10:46 PM > Subject: Beam Use Proposal > > > Dear Colleague, > > Based on the outline and a fisrt go around between a couple of people in particular the BNL group , Steve Sanders > and Michael a (still rough) draft for the beam use proposl has been written. A fair number of details in terms of luminosity estimates has still to be worked out in details, and will be done. Input on the document and strategy, as outlined both here and in the earlier shorted document is appreciated. The deadline is next Sunday (8/31) but I intend to have it complete by Friday if at all possible. > > regards > Flemming > > ------------------------------------------------------ > Flemming Videbaek > Physics Department > Brookhaven National Laboratory > > tlf: 631-344-4106 > fax 631-344-1334 > e-mail: videbaek@bnl.gov -- ----------------------------------------------------------------- Dieter Roehrich | Fysisk institutt | Email: Dieter.Rohrich@fi.uib.no Universitetet i Bergen | Tel: +47-555-82722 Allegt. 55 | Fax: +47-555-89440 N-5007 Bergen, Norway | WWW: http://www.fi.uib.no/php/drhrich.html On Mon, 25 Aug 2003, Flemming Videbaek wrote: > Hi > > some additional thoughts on RBUP - and it would be useful to get comments from other interested parties. > Afterall the plan has to be complted by the end of this week. > > In the mean time the RBUP will be corrected with several suggestons received, as well as having added > information on transverse asymmetry measurements for pp. Too I will continue to make an (internal list) for > proposed measurement to get the needed integrated luminosity better understood for 200 GeV AuAu. > One point which does need some work from the people interested is to make a real estimate how much Luminosity (not weeks) is needed to do a coalesnce measurement at high y . What rapidities can one get both deuterons and protons (not from same angle > field settings) with well defined goal of yield. > > > Certainly the trust of the 200 GeV running is high-pt and flow. (where for the latter we cannot go as high as one would really like for identified particle). The order of the priority should certainly reflect this, in particulr to measure at a place where dn/dy is roughly half of that of y~0 to reflect the change in energy density. > > > The physics addressed in the two cases is of course different. > - with a light projectile (Fe is actually more and more my own choice) one essentailly change only one parameter namely > the transverse size of the system, while the energy densities are (likely) similar, thus a reduction in high-pt yield can check this important change. > > - At low energy one will attempt to see the disappereance of high-pt suppression. From a physics point this is another > change in behaviour that can help in the understanding of partonic matter. > > So why do I prioritize (prefer) one over the other in terms of run period This basically comes to to feasibility. > Initially I also thought as JJ, but now I do not beliveve we can make a measurement above pt ~2 GeV/c (two) particular since one do need the peripheral settings to construc RCP. At pt=3 the pion yield in pp is down by ~ factor 5 and at 4 by factor 12- at the same time the luminosity is down by at least a factor of 3, and possibly by another factor of 2-3 due to the limitation in the apertures of the triplets. To put this more into perspective I have put several plots on my pii3 web-page that shows the quality of spectra d2n/dptdy (not invariant spectra) in count for specific amount of luminosity. > http://pii3.brahms.bnl.gov/~videbaek/run4/index.html > > Thus for a run period of say 5 weeks at 63 GeV we can get one reasonable spectrum of at 40 deg, and basically > one measurements at one angle/field setting with FS. So one question to answer is e.g. How important is a high y > measurement at low energy - does not y~0 (or 1) settle the issue? Too, both Star and Phenix can in about 1-day make a > measurement equivalent to our that would take 4-6 weeks, and we would have almost no other physics result at high rapidity. I still think it should be attempted, the question is when; If the coming run goes very well i.e. we get what we need > at 200 GeV, from an operational point of view you certainly would not go to another specie. A new specie clearly is for > another run period. > > On the other hand with a lighter projectile (Si, Fe) one can in the same amount time get spending ~ 2-3 weeks on high-pt > several setteings and two charge states say at two rapidities, and in remaining time measure complete distributuons of > soft physics. > > > Lastly on the observation of dn/dy of pions. I agree, one do not really need to say the pions are gaussian; They are though surprisingly close , I understand they can be described by both shifted double Gaussians as well as other parametrizations that > gives a small flat region near y~0. - in any case the <RMS> of the pion-distributions from AGS to RHIC are very close to the Landau picture e.g as discussed by Carruthers. The main point I real wanted to make was the surpise these distributions have been to many, and that we can measure these well. > > > > regards > Flemming > > ------------------------------------------------------ > Flemming Videbaek > Physics Department > Brookhaven National Laboratory > > tlf: 631-344-4106 > fax 631-344-1334 > e-mail: videbaek@bnl.gov > > ----- Original Message ----- > From: Jens Jørgen Gaardhøje > To: brahms-l@bnl.gov > Cc: gardhoje@nbi.dk > Sent: Saturday, August 23, 2003 8:00 AM > Subject: Re: Beam Use Proposal > > > Dear Flemming et al. > > A few first quick comments to the document(RBUP). > > 1) I disagree with the strong statement about Gaussian meson rap. dist. Looking at Djamels data fits with a Wood Saxon type functional is just as good. In fact the chi-squaresd is probably better. At the same time the avergage pt and the appa. T seem to be flat at |y|<1.5. I would not make a strong conclusive statement, but point out that this is what we would like to understand better. I don't think we are at the end of that story. > > 2) I feel quite strongly that our main thrust in the Au+Au runs should be to focus on the new interesting signals, e.g high pt at various rapidities, and our unique possibility to study this with identiffies particles. Related issues are the CGC search. Consequently we need long Au+Au runs at max energy for these low cross section items. > Most of the other physics can be done in a short time if we have high luminosity. Not to say that they should not be done, primarily the highest rapidities, but they should not shape the program. > > 3) I disagree with the priority given to lighter ion species over lower energy. I think it is of paramount importance > to establish the systematics of high pt. suppression. sqrt(s)=56 or better 63 is not a bad choice. > I fail to fully appreciate the significance of smaller systems as opposed to more peripheral Au+Au collisions. There may be some small second order differences, but I personally doubt that there is any major physics issue hidden there. > I propose that our request for RUN IV is AU+AU max energy and Au+Au at lower energy for (1/4?) of the time IF the preceeding full energy run has proceeded well with adequate integrated lum. The request for RUN V should include studies of p+p for the reference for high pt studies at fwd. rap, and of the pol p+p at fwd rap. > I suggest that we also include some Au+Au (possibly one could put in the lighter ion runs there) > > > Well, thats my two pennys worth. Opinions? > > > cheers > JJ > > PS: it struck me that RBUP could also be Beam Use RHIC Proposal...... > ____________________________________________________________ > Jens Jørgen Gaardhøje, Assoc. Prof., Dr. Sc. > Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark. > Tlf: (+45) 35 32 53 09, secr. (+45) 35 32 52 09, Fax: (+45) 35 32 50 16. > UNESCO Natl. Comm., secr. (+45) 33 92 52 16. > Email: gardhoje@nbi.dk. > ____________________________________________________________ > > > ----- Original Message ----- > From: Flemming Videbaek > To: brahms-l@bnl.gov > Sent: Friday, August 22, 2003 10:46 PM > Subject: Beam Use Proposal > > > Dear Colleague, > > Based on the outline and a fisrt go around between a couple of people in particular the BNL group , Steve Sanders > and Michael a (still rough) draft for the beam use proposl has been written. A fair number of details in terms of luminosity estimates has still to be worked out in details, and will be done. Input on the document and strategy, as outlined both here and in the earlier shorted document is appreciated. The deadline is next Sunday (8/31) but I intend to have it complete by Friday if at all possible. > > regards > Flemming > > ------------------------------------------------------ > Flemming Videbaek > Physics Department > Brookhaven National Laboratory > > tlf: 631-344-4106 > fax 631-344-1334 > e-mail: videbaek@bnl.gov -- ----------------------------------------------------------------- Dieter Roehrich | Fysisk institutt | Email: Dieter.Rohrich@fi.uib.no Universitetet i Bergen | Tel: +47-555-82722 Allegt. 55 | Fax: +47-555-89440 N-5007 Bergen, Norway | WWW: http://www.fi.uib.no/php/drhrich.html
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