Re: [Brahms-l] 63 AGeV results

Hi Ionut and others,

I think that it is ofcourse up to the data to see if 
dN/dy \propto s^(0.25) or s^(0.5)
BTW this is the total dN/dy, so that in the Landau picture you would 
expect dN/dy (y=0) to be bigger since the width of the distribution is 
smaller at 63AGeV. One nice paper about the Landau model is the one by 
Peter Steinberger:
http://xxx.lanl.gov/abs/nucl-ex/0405022
Unfortunately I have not found a good paper for an experimentalist like me
about these things and most original papers are in russian.

To check your results at y=0 it is also good to look at 
Total dN/dycharged (y=0) = N_pi+- + N_K+- + N_pp-bar ~ 1.2 dN/deta 
charged (eta = 0)
If you draw a y-pT histogram and plot the acceptance for eta = -1 - +1, 
you 
can convince yourself that the dN/dy yield is larger. The factor 1.2 
depends on the p_T distribution and as I remeber 1.2 is a good assumption.
Then I would also check pi/K which should agree with the systematics 
observed. Your K/pi~24/165~14.5 looks ok, while my K/pi~100/160~0.63 looks 
absolutely wrong and I now realise that in the meson paper was plottet K*4 
so that my estimate for your data would be 25, which agrees quite well;)

Cheers,
   Peter


On Mon, 21 Mar 2005, Ionut Christian Arsene wrote:

> 
>    Hi Flemming, Peter,
> 
>   Thank you for your prompt reply. I'm trying now to find what could be
> wrong in my analysis. The problem at mid-rapidity seems to be the biggest
> one since I get pion ratios significantly different than 1.
>   First I want to point out the rough results that come out from the
> analysis. At 0-10% centrality, around mid-rapidity, the yields are:
>   165 for pions,
>   ~24 for kaons,
>   ~17 for protons,
>   ~8 for anti-protons.
>  The ratios are
>   ~1 for pions,
>   0.9-0.95 for kaons,
>   ~0.5 for pbar/p.
>  The net proton yield at mid-rapidity is aprox. 9 (at 200GeV was 7).
>  At least for mesons the numbers seems to be right, following the Landau
> formula, as Peter said.
>    The corrections that I used are: acceptance, tracking efficiency (only
> for FS because it seems that in the dst version that I used the MRS hits
> was not available and I could not use Truls's curves), pid efficiency,
> decay, multiple scattering and absorption for anti-protons. The acceptance
> maps are maked with the 'generateMaps' script. I think is basicly Peter's
> work.
>    As Trine suggested, for the MRS, I tryied to use only data from one
> polarity at a time, e.g. \pi^{+} only from A polarity settings, and
> compare the results. Doing this I observed a correlation between
> the setting that I used and the resulting yield. The spectra is very well
> fitted at mid-rapidity, so maybe this can come from the acceptance maps?
> 
>               Ionut
> 
> P.S. Please reply at this address, since my address from the brahms-l
> seems not to be available at the moment
> 
> 
> On Fri, 18 Mar 2005, Peter H.L. Christiansen wrote:
> 
> > Hi Ionut,
> >
> > A few comments:
> > If it is possible I would make a 0-5% sample, becuase it is well known
> > that theorists (ok, most people) only remember values for this centrality
> > class.
> >
> > I think that for a fixed centrality class dN/dy \propto s^(0.25) (Landau)
> > so that you would expect the yields to be sqrt(63.0/200.0)~0.56 times the
> > 200 GeV yields. We published ca. dN/dy(y=0)=290 pions and dN/dy(y=0)=180
> > kaons, so I would expect your yields to be roughly 160 and 100. The fit to
> > the dN/dy curves should be done with Gaussians with fixed mean (0) or at
> > least be symmetrical in y (K+ looks strange). There you could compare the
> > width to the Landau estimate: sigma^2 = ln (gamma_beam).
> >
> > If I were you I would focus on 1 specie e.g. pions where statistic is not
> > a problem. Then I would cut down on centrality classes and do maybe 0-5%
> > and 30-40%.
> >
> > About pions:  As Flemming writes more details are needed, but what is a
> > great idea (and not so difficults) is to make a plot of the yield in the
> > acceptance range which should be damn close for pi+ and pi- (if you use
> > the same range) and then the extrapolated yield from the fit, so that you
> > can see the acceptance coverage. It is fx. clear that your fits don't have
> > the same shape for pion spectra which is usually the case (both as a
> > function of rapidity and centrality).
> >
> > I think there is a really good story with the pion yields alone.....
> >
> > Cheers,
> >    Peter
> >
> > P.s: I'm really looking forward to the final net-proton spectra!!!!!
> >
> > On Fri, 18 Mar 2005, Ionut Christian Arsene wrote:
> >
> > >
> > >      Hi all,
> > >
> > >    I obtained some results from the Au+Au 63 AGeV data run. A part of the
> > > graphs are posted at the following address:
> > >   http://www4.rcf.bnl.gov/~aic/.
> > > In the next days I will update the page with new plots.
> > >    I would like to present these results at the workshop that will take
> > > place in Bergen at the end of this month, so I will appreciate your
> > > comments and sugestions about these results.
> > >
> > >              Regards,
> > >                 Ionut
> > >
> > >
> > > _______________________________________________
> > > Brahms-l mailing list
> > > Brahms-l@lists.bnl.gov
> > > http://lists.bnl.gov/mailman/listinfo/brahms-l
> > >
> >
> > --
> > :-) --------------------------- )-:
> >  Peter H L Christiansen
> >  pchristi@nbi.dk / (+41)764870425
> > :-D --------------------------- \-:
> >
> >
> >
> 

-- 
:-) --------------------------- )-:
 Peter H L Christiansen
 pchristi@nbi.dk / (+41)764870425
:-D --------------------------- \-:


_______________________________________________
Brahms-l mailing list
Brahms-l@lists.bnl.gov
http://lists.bnl.gov/mailman/listinfo/brahms-l