Re: [Brahms-l] meson paper

Howdy Djamel et al.

Djamel Ouerdane wrote:
> -weak decay corrections: I haven't done that and I believe that if I am
> to do it, this will delay the paper a great deal. On the other hand,
> things are maybe not so bad, I remember a correspondence with Becattini,
> Dieter and Jens Ivar and I swear I saw numbers :) so it means that someone
> took a stab at it (Jens Ivar ?). If numbers exist, I'm willing to put
> them in. I think the real issue is K0. Isospin conservation tells us that
> we have N(K+) = N(K0) and N(K-) = N(K0bar). How many decay early enough to
> pions that are seen by the spectrometers ? If someone can make a short
> brag simulation, I would be infinitely grateful :)

The weak decay correction has clearly some effect. Whether it should be 
called bad or not so bad I will not be the judge.  But they are significant.

Here are some snippets from communication with Becattini where he has 
fitted BRAHMS data:

a) Assuming all weak decay products are detected:

For the 4pi fit:
T         = 154.7 +- 2.6 MeV
muB/T     = 0.634 +- 0.028
gamma_S   = 0.888 +- 0.017
 From T and mu_B and taking into account the correlation
-->  mu_B = 98.1 +- 3.0 MeV

The results for the midrap fit are as follows:
T         =  149.3 +- 1.4 MeV
mu_B/T    =  0.143 +- 0.035
gamma_S   = 0.893 +-  0.018
-->  mu_B = 21.4 +- 5.1 MeV

b) Quoting Becattini:

by switching OFF weak decays and keeping the same data
points as in the previous fits, I get a consistently higher
temperature (an effect that I observed some time ago, as
I mentioned in the previous message). Other parameters
seem to be less affected by this change.

At midrap:

T = 170.3 +- 2.5 MeV  (20 MeV higher !)
gS = 0.837 +- 0.016            chi2 = 3.1/2
muB = 23.5 +- 5.1 MeV

In 4pi:

T = 164.6 +- 5.7 MeV
gS = 0.834 +- 0.015           chi2 = 5.4/2
muB = 91.4 +- 4.0 MeV

c) Using some rough Oslo estimates from simulations run by Trine of the 
decay products we see in our spectrometers, still quoting Becattini:

taking 85% of the pions from K0s and 60% from
Lambdas,Sigma+-,Xi- in 4pi and 90%,70% at midrap
I get:

At midrap:

T = 148.2 +- 1.3 MeV
gS = 0.864 +- 0.017            chi2 = 3.4/2
muB = 21.9 +- 4.9 MeV

In 4pi:

T = 153.4 +- 4.4 MeV
gS = 0.848 +- 0.018           chi2 = 0.97/2
muB = 96.4 +- 4.3 MeV

Best wishes from
Jens Ivar

-- 
           _____________________________________________________
  ________|                  Jens Ivar Jørdre                   |_______
  \       | Dept. of Physics                        Office: 521 |      /
   \      | Allégt 55                    Phone: +47 55 58 27 92 |     /
    \     | 5007 Bergen                    Fax: +47 55 58 94 40 |    /
    /     | Norway            E-mail: jensivar.jordre@fi.uib.no |    \
   /      |_____________________________________________________|     \
  /__________)                                               (_________\

                          "To be or not to bop"
                            (Dizzy Gillespie)


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