[Frost] Prospects for Double Pions in Deuterized Butanol

[Igor Strakovsky]

Mike,

Let me add that the neutron efficiency depends from the threshold of
the registration.  I do not know exactly CLAS value

Igor

On Sun, 30 May 2010 23:17:04 -0400 (EDT), Michael Dugger <dugger at jlab.org> 
wrote:

> 
> 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