Tancredi:
I am still puzzled as why we only have 4 runs for the very good beam
period of Saturday afternoon till Sunday morning (1.5 shifts)? Was it
the wire chambers charging up? The beam was quite good and my
understanding is that the BQM's were within the spec.
Manouchehr
Manouchehr
Tancredi Botto wrote:
>
> Willing to put up a fight, and appreciating the difference between
> measuring something consistent with zero against the odds of having a 100%
> unpolarized target (also, the 100% molecules scenario is rather
> unsatisfying) I went back to the "final" results before calling them
> final. Also, since only the WFT unit switches on/off in the target, we are
> likely to retain at least the polarization of state1, were the WFT and
> thus state3 completely wrong.
>
> The first two attachments are an asymmetry, in the L and R blast sector
> and as a function of scatterd electron angle, consistent with a product of
> Pe*Pt = 0.05. Being generous (60% beam polarization) this is consistent
> with an 8% vector polarized H target. Of course the actual nuclear
> polarization of atoms is higher if we allow for molecular dilution. In
> particular, the number above corresponds - by eye- to a decent confidence
> level in terms of X2.
>
> The are two main differences from results shown recently:
>
> _ I allowed for a sign error in either the helicity or the target. In
> other words I allowed that one of the spin directions is attributed
> wrong. Indeed this may be for the beam helicity, it has to be checked
> out against compton and "unfortunately" we most often flip the beam
> helicity during a run. I hope we have compton for runs 564-567 but I'd
> not know how to replay them (...). We are sure about the holding field
> direction (beam left) and the sign of the target state.
>
> _ I ventured in a cerenkov cut, assuming of course it is not spin
> dependent, and you can see I have a rather clean sample in the second
> plot (the correlation of L/R sector angles for elastic events in either
> sector). Note that the cerenkovs are still not in their optimal setting.
> however now they are shielded fromthe B field. Note also that we may not
> be critically dependent on the CC only, since with better reconstruction
> we could apply cuts on kinematically overdetermined elastic scattering
>
> Other comments:
> _ our small measured value and our "false asymmetries" conspire for a
> large (relative) systematic error
> _ My definition of false asymmetries (see yesterday) is not very solid,
> since such "asymmetries" are of type (0 - 0)/(0 + 0) which can become
> uncontrollable. But nevertherless they are small.
> _ We simply have no sufficient data (only 4 runs sunday 27) for an
> analysis of the asymmetry for runs with fixed spin directions.
> - hope we get beam soon! tomorrow I'll be reachable by email.
>
> grinning,
> -tancredi
>
> --
> ________________________________________________________________________________
> Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
> research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
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--____________________________________________________________________ Manouchehr Farkhondeh manouch@mit.edu Principal Research Scientist Division Head of Physics, Accelerator MIT, Bates Linear Accelerator Center tel (617)253-9298 Middleton, MA 01949 fax (617) 253-9599 ____________________________________________________________________
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