[Frost] Prospects for Double Pions in Deuterized Butanol

[Igor Strakovsky]

Dear FROSTies,
  
There are several facts in recent pol measurements.  I think that is good
to consider Eg = 1.1 and 2 GeV cases for FROSTd in July first of all.  The
attractive reactions are: gn-->pi-p, pi+(pi-n), and KLambda.
  
http://alosha.phys.va.gwu.edu/~igor/mytalk/2010/FROSTb.pdf

Cheers, Igor
  
> On Wed, 26 May 2010 18:12:38 -0400 (EDT), Volker Crede 
><crede at hadron.physics.fsu.edu> wrote:
> 
>> Dear Eugene,
>> 
>> you suggested this morning the possibility to study double-pion production 
>>with a deuterized butanol target. I have attached some pictures from g9a 
>>using a lineary-polarized beam with a coherent edge at 1.3 GeV; only one 
>>target orientation has been used (L-+,<=) to make these distributions. For 
>>this polarization configuration, we have a total of 5 observables (all 
>>degrees of polarization are set to 1.0):
>> 
>>  I = I_0 ( ( 1 + P_z ) +
>>       sin [ (2 beta) (I_s + P^s_z) ] + cos [ (2 beta) (I_c + P^c_z) ] )
>> 
>> The picture 'I_s_energyIndex13.eps' shows (very, very preliminary) the 
>>combination of (I_s + P^s_z), i.e. the combination of the beam asymmetry I_s 
>>(that Chuck Hanretty has been extracting from g8b data) and the new
>> beam-target observable P^s_z. The photon energy is [1100, 1150] MeV; the 
>>observable is plotted versus phi*, which is the azimuthal angle of the pi+ in 
>>the rest frame of the two mesons. The different distributions show the 
>>binning in the corresponding cos(theta*) variable (pretty much the same thing 
>>that Chuck always shows). It starts out very flat, but polarization effects 
>>are clearly visible at larger values for cos(theta*).
>> 
>> The other two pictures show the missing proton peak integrated over all bins 
>>(only pi+ and pi- detected) as well as the lab_beta modulation for just 0.1 < 
>>cos(theta*) < 0.2 and the corresponding fourth data point in there ... a very 
>>fine binning.
>> 
>> These are distributions for double-polarization and with a pretty fine 
>>binning in three of the 5 independent variables. The statistics is very
>> good. No background subtraction has been performed and there is still a lot 
>>of background involved (of the order of 50%). The total cross section for 
>>two-pion production off the proton is of the order of 40-60 microb for this 
>>energy range; the cross sections off the neutron are about 60-70% of the 
>>proton cross sections ... still pretty big. Most important, the attached 
>>distributions are based on just 35 hours of data-taking ... less than two 
>>days. The total number of events for PARA is 179,647,134 and for PERP is 
>>163,187,819.
>> 
>> If we decide to go with just 1.1 GeV or 0.9 GeV coherent-edge position, the 
>>count rates should even be better. This corresponds to the 1500-1700 MeV mass 
>>region, very interesting to study for example N* decays into Delta pi, which 
>>are poorly understood for many states. Delta-pi decays in D-wave seem to be 
>>stronger or equal in strength to Delta-pi decays in S-wave ... not expected 
>>from naive phasespace arguments. This could be part of a physics motivation.
>> 
>> Best wishes
>> 
>>    Volker