Dear collaborators,

I am posting the final version of my Ph.D. thesis.  The title and
abstract are given below.


Regards,

Wendy Taylor
University of Toronto



	   A Measurement of b-quark Fragmentation Fractions
	       in pbar-p Collisions at sqrt{s}=1.8 TeV


Fragmentation   is the process   by  which quarks and gluons  organize
themselves into  hadrons.  The fragmentation  properties of the bottom
quark cannot  be predicted from fundamental  principles and hence must
be determined empirically.  We  investigate one such property,  namely
the flavour dependence of the fragmentation  process for bottom quarks
produced in    1.8-TeV   proton-antiproton collisions.   This  flavour
dependence is investigated  by  determining the $B$-hadron  production
ratios.

We  use   a sample  of  pbar-p  data   corresponding to  an integrated
luminosity of 110 pb^{-1} and  reconstruct the following  semileptonic
B-hadron  decays into electrons and  charmed hadrons:  B^+ -> e^+ nu_e
{Dbar}^0 X, B^0 -> e^+ nu_e D^{*-} X, B^0 -> e^+  nu_e D^- X, B^0_s ->
e^+ nu_e D_s^- X  and  {Lambdabar}^0_b -> e^+ nu_e Lambda_c^- X.  With
these data, we measure the ratios of fragmentation fractions

     f_d/f_u         =   (88 +\- 21)%,
   f_s/(f_u+f_d)     = (21.5 +\- 7.1)% and
f_{baryon}/(f_u+f_d) = (12.0 +\- 4.2)%.

Assuming that     these    four  hadrons   saturate   production    of
weakly-decaying B hadrons, that is, that f_u  + f_d + f_s + f_{baryon}
= 1, we determine

      f_u  = (39.8 +\- 5.4)%,
      f_d  = (35.2 +\- 4.8)%, 
      f_s  = (16.1 +\- 4.5)% and
f_{baryon} =  (9.0 +\- 2.9)%.

These  results  represent the first  measurement   of all four b-quark
fragmentation fractions in a single  experiment.  These fractions  are
in agreement  both with  previous phenomenological interpretations and
with other experimental measurements.
















Posted to /cdf/pub/thesis/cdf4913_bfrag_thesis.ps
    http://www-cdf.fnal.gov/thesis/cdf4913_bfrag_thesis.ps

Posted by wendyt@cdfsga