[Frost] Prospects for Double Pions in Deuterized Butanol

[Bill Briscoe]

Yes, this is very important to realize. 

----- Original Message -----
From: Michael Dugger <dugger at jlab.org>
Date: Sunday, May 30, 2010 11:17 pm
Subject: Re: [Frost] Prospects for Double Pions in Deuterized Butanol
To: Eugene Pasyuk <pasyuk at jlab.org>
Cc: frost at jlab.org

> Hi,
> 
> The neutron efficiency is highly dependent on the momentum. The EC 
> gets an 
> efficiency for protons of ~50% when the momentum is about 1.8 GeV. For 
> a 
> neutron with a momentum of 1 GeV we only get an efficiency of ~25% At 
> 0.6 
> GeV momentum the efficiency drops to ~10%.
> 
> -Michael
> 
> On Sun, 30 May 2010, Eugene Pasyuk wrote:
> 
> > 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
> >>
> >>
> >>
> >> _______________________________________________
> >> Frost mailing list
> >> Frost at jlab.org
> >> 
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> > 
> >
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