From: Ian Bearden (bearden@nbi.dk)
Date: Tue Oct 22 2002 - 01:53:50 EDT
Hi Alle, Flemming, how thick is the trigger counter used in the p+p running? I guess it is similar to the beam pipe, thus you see twice (roughly??) the background in p+p than in Au+Au. Also, I think that one way we can check to see how low we can 'trust' the d is too look at the ratio of dbar to d. I think that this should be flat, since the pbar to p is flat. Where this ratio starts to fall (in pt) is where the background contribution to d starts to become problematic. On a related note, you should keep in mind that one of the reasons that STAR doesn't show deuteron coalescence is that they cannot (at least they have not shown, as far as I know) measure protons. As for NA44, we did not have the same constellation of issues that we have in BRAHMS. In particular, our target was not in a beam pipe, but was in air. And (we believe!) our tracking was good enough to reject tracks which did not originate from the target position. We were also looking at ds with a quite higher momentum than in the MRS (roughly 4-12GeV/c, as opposed to 0-2GeV/c). So NA44 experience doesn't help so much for the MRS, the FS on the other hand is not so dissimilar to NA44. Cheers, Ian -------------------------------------------------------------------- | I.G. Bearden | | Niels Bohr Institute Tb 3 email: bearden@nbi.dk | | Blegdamsvej 17 phone: (+45) 35 32 53 23 | | København Ø FAX: (+45) 31 42 10 16 | | Danmark Www: http://www.nbi.dk/~bearden | -------------------------------------------------------------------- -----Original Message----- From: owner-brahms-soft-l@bnl.gov [mailto:owner-brahms-soft-l@bnl.gov]On Behalf Of Flemming Videbaek Sent: 19. oktober 2002 02:40 To: brahms-soft-l@bnl.gov Subject: Re: deuterons etc.. I just want to inject one observation based on the pp data. In pp there is a significant yield of deuterons - and in pp this MUST be from background, probably this is from the trigger counters+beam pipe- thus one should be very concerned about a similar contributions in Au+Au. I think it is not known how well geant describe deuterons from background - but I do not think this is small based on the pp results. I it also worthwhile to note that STAR did not present deuteron results but only anti-deuterons that are free from such contributions . I would think that the effect on deuterons due to absorbtion, etc roughly goes by p/2 i.e the effect for a given momentum deuteron is similar to that of a p/2 proton- this means that for p<1 GeV/c deuterons these corrections are large, nad one should not consider those. Thus any consideration should only look at p(d) > 1.2 GeV/c in my opinion. I looked briefly at the geant code from fluka,... and I do not see any straight forward to include this in the simulation. One suggestion I have is that some-one contact one the of exp. at CERN that looked at anti-deuteron production at theta~0 - and I do not mean NA44 (I guess primarely beacase the comments from there seems not to give clues to this problem). 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" <gardhoje@nbi.dk> To: <brahms-l@bnl.gov> Sent: Friday, October 18, 2002 5:43 PM Subject: Fw: deuterons etc.. > > > > > > Dear friends, > > > > The problem at hand that Marco is struggling with concerns estimating the > > corrections to p, pbar, d and anti-d in view of > > correcting the raw measured B_2 and B_anti-2 derived from the basic yields > > of these particles after acceptance correction etc. > > All for the MRS and for now at 90 deg. > > > > Let me try to summarize my understanding of these corrections and of their > > relative importances for the sake of discussion. > > All input is welcome. > > > > The experimental quantity B_A is proportional to the ratio (dN_A/dp_A) / > > (dN_p/dp_p)**A, neglecting energy dep. prefactors. > > Thus is follows directly from the measured yields of identified particles > > after correction for geometrical acceptance, contamination from > > secondary particles (produced and due to decays), absorption (in material > > between the collision vertex and the final PID detector) and decay losses > > (not applicable here). > > > > Production contribution: > > to protons: > > These can be ejected from the beam pipe and produced in secondary > reactions > > with other detectors, magnets etc... They can originate from knock-out > > reactions on nuclei or from pair production in a dense medium. Both pi, K, > > and p (and their antiparticles) can contribute to this. Thus the effect > can > > be simulated by generating particles in the MC according to spectra > > distributions with slopes and yields close to those which we have measured > > in the MRS. > > to deuterons: > > I would expect that there is a finite (but small) contribution to the > > deuteron yields from knock out from very light nuclei (mainly the Be > pipe). > > The energy required to produce a d and d-bar pair (4GeV) is so large that > > the yield from this source must be vanishing. > > to antiprotons: > > since there are not antiprotons present in the material surrounding the > > experiment the only contribution can be pair production.. this requires at > > least 2 GeV of primary energy, thus the effect must be relatively much > > smaller than for protons. > > to antideuterons: > > Since there is no knock out possible, the only contribution is from > > pairproduction. It is presumably of exactly the same magnitude as for d. > > > > Decay (feed down) contributions: > > to protons: > > These originate mainly from the decay of baryonic resonances (hyperons > > etc..). STAR has measured the Lambda yield (Lamda/p=1/2 ?). The > contribution > > from protons from such decays in our acceptance needs to be estimated. > This > > may be the most important contribution to the B2 corrections. > > to antiprotons: > > Similar. Star has measured antilambda/lambda (= 3/4 ?). > > to deuterons and antideuterons: > > unimportant. Only source I could think of is fragmentation of heavier (and > > rarer) clusters. > > > > Absorbtion contributions: > > to protons: > > absorption in pipe and in air mostly. > > to deuterons: > > idem. The main effect is presumably the larger cross section of the > > deuteron. Some estimate of this can be optained by looking in the review > of > > part. physics p. 208 and following. At E_p > 1Gev the pd cross section is > a > > factor of two larger than for pn collisions. So roughly the deuterons is > > twice the size of the nucleon - not surprisingly. > > to antiprotons: > > significant contribution due to absorbtion in the pipe and in air (at low > > momenta) > > to antideuterons: > > the absorbtion contribution should resemble that for antiprotons, but with > a > > higher cross section. I would expect that for large antideuteron energies > > ( > 1 GeV) the absorption is twice that for antiprotons (in relative > terms). > > At lower energies the Coulomb interaction plays a dominant role. But, a > > reasonable approximation is probably still to take the antiproton > absorbtion > > and multiply by two (for comparable CM energies) since the neutron does > not > > contribute to the total charge. > > > > All of these corrections are momentum dependent, i.e. dependent on the > input > > momentum of the particles. > > > > Since we have a good Monte Carlo description of the experiment, the > natural > > course of action seems to me to create a full calculation with a mix of > the > > approximately correct yields and spectrum slopes of the original particles > > and antiparticles, letting decays be operational, and then for each > particle > > type (p, d, pbar, dbar) of interest to take the ratio of the input > spectrum > > and the accepted/reconstructed spectrum after PID in TOFW. This results in > > the momentum dependent correction factors to be applied to the spectra > > before calculating the B2. As mentioned above the antideuterons present a > > problem, but I would probably apply the antiproton correction up to 0.5 > GeV > > ( the antiproton dominates the Coulomb part) and then twice that at higher > > energies (above 1GeV). > > > > This could either be done with a mix of thermal spectra or with a large > > HIJING sample of events (we know that HIJING is quite OK at mid-rapidity). > > HIJING events are probably too small to allow for a reasonable d study. > > > > hope this is of some use > > cheers > > jj > > > > ____________________________________________________________ > > 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: <murray@comp.tamu.edu> > > To: <brahms-dev-l@bnl.gov> > > Sent: Friday, October 18, 2002 12:23 AM > > Subject: Re: deuterons in brag > > > > > > > Can one not take the approach that if the dbar hits anything hard it > > > will split up into an nbar and pbar. Thus one could create a dbar in > > > GEANT and then check everytime GUHADR if it is scheduled to have a > > > hadronic interaction. At that point one could kill it and transform into > > > a pbar and nbar. > > > Alternatively one can do the analysis separely for dbars and nbars > > > at least when you are out of the magnetic fields. > > > Michael > > > > > > Quoting Flemming Videbaek <videbaek@sgs1.hirg.bnl.gov>: > > > > > > > Hi > > > > To the best of my knowledge anti-deuterons are not defined in geant ! > > > > One can certainly define a particle being a anti-deuteron, and one can > > make > > > > it behave properly in regard > > > > to multiple scattering, energy loss and tracking - but NOT for > hadronic > > > > integraction (and absorbtion) which > > > > requires a proper interface to the tracking part of hadronic > > interaction. > > > > Good but tough problem. > > > > > > > > Flemming' > > > > ------------------------------------------------------ > > > > Flemming Videbaek > > > > Physics Department > > > > Brookhaven National Laboratory > > > > > > > > tlf: 631-344-4106 > > > > fax 631-344-1334 > > > > e-mail: videbaek@bnl.gov > > > > ----- Original Message ----- > > > > From: "Marco Germinario" <germina@hilux17.nbi.dk> > > > > To: "Flemming Videbaek" <videbaek@sgs1.hirg.bnl.gov> > > > > Sent: Thursday, October 17, 2002 4:35 PM > > > > Subject: Re: deuterons in brag > > > > > > > > > > > > > > > > > > Hi Flemming, > > > > > I've been looking at the Geant manual, and the deuteron number is > > 45.Th > > > > > e problem is I can't find out how to throw antideuterons,and how to > > > > > rethreive them,if f ex i want to find the ratio between thrown and > > > > > accepted antideuterons. And at which point I should issue the > command > > > > > cont/print part 0 ? > > > > > Thanks > > > > > Marco > > > > > > > > > > > > > > > > > > > > > > > > > On Tue, 15 Oct 2002, Flemming Videbaek wrote: > > > > > > > > > > > This kind of stuff can be looked up in the Geant html > description - > > or > > > > when > > > > > > running brag > > > > > > issue an cont/print part 0 that will print all the particles that > > geant > > > > > > knows of. > > > > > > Deuteron are '42' > > > > > > > > > > > > > > > > > > ------------------------------------------------------ > > > > > > Flemming Videbaek > > > > > > Physics Department > > > > > > Brookhaven National Laboratory > > > > > > > > > > > > tlf: 631-344-4106 > > > > > > fax 631-344-1334 > > > > > > e-mail: videbaek@bnl.gov > > > > > > ----- Original Message ----- > > > > > > From: "Marco Germinario" <germina@hilux03.nbi.dk> > > > > > > To: <brahms-dev-l@bnl.gov> > > > > > > Sent: Tuesday, October 15, 2002 2:36 PM > > > > > > Subject: deuterons in brag > > > > > > > > > > > > > > > > > > > > > > > > > > I'm making some knock out simulations for the beam pipe in > > brag,and > > > > have > > > > > > > to look at protons and > > > > > > > deuterons produced, vs pt.Does someone know which is the id > number > > > > for > > > > > > > deuterons,if brag take it into account,or if some special > > procedure > > > > before > > > > > > > to launch the simulation has to be taken? > > > > > > > Thanks, > > > > > > > Marco > > > > > > > > > > > > > > -- > > > > > > > > > > > > > > Marco Germinario > > > > > > -------------------------------------------------- > > > > > > > University address : Personal address > > > > > > > : > > > > > > > Niels Bohr Institute : Noerre Alle' 75,518 > > > > > > > Blegdamesvej 17,Ta-2 : Egmont kollegium > > > > > > > Copenhagen, Danmark : 2100 Copenhagen > > > > > > > Mail: germina@nbi.dk : Danmark > > > > > > > Tlf : + 45 35325305 : Tlf: +45 82320518 > > > > > > > > > > > > > > Mob: +45 26720446 > > > > > > --------------------------------------------------- > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > Marco Germinario > > > > > -------------------------------------------------- > > > > > University address : Personal address > > > > > : > > > > > Niels Bohr Institute : Noerre Alle' 75,518 > > > > > Blegdamesvej 17,Ta-2 : Egmont kollegium > > > > > Copenhagen, Danmark : 2100 Copenhagen > > > > > Mail: germina@nbi.dk : Danmark > > > > > Tlf : + 45 35325305 : Tlf: +45 82320518 > > > > > > > > > > Mob: +45 26720446 > > > > > --------------------------------------------------- > > > > > > > > > > > > > > > > > > > > > > > > ------------------------------------------------- > > > This mail sent through IMP: http://horde.org/imp/ > > > > > > > > > > > > > >
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