[Frost] Prospects for Double Pions in Deuterized Butanol

[Eugene Pasyuk]

Volker,

In case of deuterium target we will have to detect all three particles, 
pi+, pi- and neutron. Neutron detection efficiency in EC is about 50% 
and about 10% in TOF. Also momentum resolution for neutrons obviously is 
not as good as for charged particles.
We should take 3 perticle topology from g9a as a start pint for 
estimates. An then drop it by a factor of 10 or so.
If we go with deuterium target it makes sense to bring LAC on-line to 
have better efficiency for neutrons.

-Eugene


On 5/26/10 6:12 PM, Volker Crede 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
>
>
>
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