Re: [Brahms-l] lambda/p ratio vs rapidity

Hi JH,

I agree with you.

Cheers,
  Peter

On Thu, 2009-08-13 at 12:49 -0400, J.H. Lee wrote:
> Hi, Peter,
> 
> Isn't the condition  K^+ - K^- ~ Lambda  - Lambda_bar at each
> rapidity 
> coming from local strangeness conservation rather than chemical
> equilibrium ?
> If we assume strangeness is only carried by lambdas and kaons and
> conserved, 
> s - s_bar =  (K^- +  Lambda) - (K^+ + Lambda_bar) =  0
> K^+ - K^-  =  Lambda  - Lambda_bar,
> which doesn't explicitly need chemical equilibrium.
> 
> JH
> 
> Peter Christiansen wrote: 
> > Dear Michael,
> > 
> > I have tried to play with these things from another angle once
> > (following chemical ideas of BRAHMS, you, and others) that might be
> > useful. If you would have chemical equilibration at each rapidity you
> > would expect:
> > K^+-K^- ~ Lambda - Lambda-bar
> > 
> > If I look at NA49 data this does not seem so bad an estimate, see
> > attached plot (there is one of the data sets where the centralities are
> > not the same for Ks and Lambdas as I remember).
> > 
> > It might not help you to get p/Lambda (or the pT dependence - I think
> > Flemming has done some work on this), but it might give some cross
> > check:-)
> > 
> > Cheers,
> >    Peter
> > 
> > On Wed, 2009-08-12 at 17:15 -0500, Michael Murray wrote:
> >   
> > > Dear Casper,
> > >                   BRAHMS has found that the strange chemical  
> > > potential m_s = 0.28 +- 0.04 * m_q
> > > Since lambda is like a proton that has an up quark changed to a  
> > > strange quark then lambda/p is proportional to exp (mu_s - mu_q) =  
> > > exp (0.72 mu_q)  or (pbar/p)**0.12
> > > 
> > > Given the change of pbar/p from 0.75 to 0.23 from y=0 to y=3.1 I find  
> > > that the lambda/proton ratio should decrease by a factor of 0.86+-0.02
> > > 
> > > The antilambda/antiproton ratio should INCREASE by this factor.
> > > 
> > > This seems like a reasonable estimate for the overall change in the  
> > > ratio. I will work on the Pt dependence next.
> > > Michael
> > > 
> > > 
> > > 
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-- 
Peter Christiansen
Email: peter.christiansen_at_hep.lu.se
Phone: (+46) 046-2227709

Address:
Lund University
Department of Physics
Div. of Experimental High-Energy Physics
Box 118
SE-221 00 Lund
Sweden


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