Dear Jens,
Gordon Baym once said that a great hope of relativistic
heavy ions was that we might finally be able to cleanly
separate sourcesas a function of rapidity. The thermal modelers
at RHIC are already implicitly doing this when they use spectra
and ratios at y=0 for there fits, thus avoiding all the messy
(and so far unpublished) forward rapidity measurements.
It is quite possible that a fluid element at y=3 will lose
communication with its cousin at y=0 before it achives chemical
equilibrium. Uli Heinz was doing this years ago.
If this is the case then we can do our chemical analysis
versus rapidity and the answers will change. NA49 has raised
a resonable objection to this by noting that even in pp the rapidity
distributions of k- and k+ are not the same. However in the
limit of an infinite rapidity range this difference would
become irrelevent. While dY=3 is not infinite it is large compared
to the difference in the widths of the k- and k+ yields from
pp collisions.
Put another way if all particles produced for a nucleon-nucleon
collison whose center of mass was at y_cm were ejected at y_cm
then we could study the chemical equilibration in very fine
intervals of y. However if the underlying pp collision produces
particles over a width of dy then that sets a minimium scale
of our resolution for measuring changes in y.
Yours Michael
Quoting Jens Jørgen Gaardhøje <gardhoje@nbi.dk>:
> Hi Michael,
> I have a problem with the thermal model at fwd rap.
> If we argue that the drop is due to a '2 source picture', then we cannot
> use
> a thermal model to extract any meaningfull chem. pots.
> Indeed, we (I) claim that the drop of the K and p ratios at fwd rap. are
> due
> to the inclusion of
> direct processes in addition to pair prod. I am not sure that I would
> venture the claim that also the
> particles of direct origin are in chem. and thermal eq. with the rest.
> Do you agree?
> JJ
>
> ----- Original Message -----
> From: "Michael Murray" <murray@cyclotronmail.tamu.edu>
> To: <brahms-l@bnl.gov>
> Sent: Tuesday, May 14, 2002 7:19 PM
> Subject: Re: QM02 abstract
>
>
> > Dear Peter,
> > why not give some hint of what the thermal models
> > say about our forward data? What is happening to mu_q and mu_s
> > as we go forward?
> > Michael
> >
> > Quoting "Peter H. L. Christiansen" <pchristi@nbi.dk>:
> >
> > > Hi
> > >
> > > I would like to get the collaboratiosn comments on an abstract I
> will
> > > submit for QM02 tomorrow on charged particle ratios. Comments have
> to
> > > here
> > > before 10 tomorrow (european time).
> > >
> > > http://www.nbi.dk/~pchristi/BRAHMS/abstract.ps
> > > or
> > > http://www.nbi.dk/~pchristi/BRAHMS/abstract.pdf
> > >
> > > Cheers
> > > Peter
> > >
> > > --
> > > :-) --------------------------- )-:
> > > Peter H L Christiansen @ NBI
> > > EMAIL : pchristi@nbi.dk
> > > OFFICE : Tb1@NBI (353 25269)
> > > HOME : Hjertensfrydsgade 3, st
> > > PHONE : 33330493(New)/ 40840492(mob.)
> > > :-D --------------------------- \-:
> > >
> >
> >
> >
> > Michael Murray, Cyclotron TAMU, 979 845 1411 x 273, Fax 1899
> >
> >
>
Michael Murray, Cyclotron TAMU, 979 845 1411 x 273, Fax 1899
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