From: Flemming Videbaek (videbaek@sgs1.hirg.bnl.gov)
Date: Fri Oct 18 2002 - 20:40:13 EDT
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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