[Hallc] [EXTERNAL] Backward-angle Exclusive pi0 Production above the Resonance Region

[gabriel at jlab.org]

Dear all-
thank you for your kind invite. Yes, I would like to join in this efforts.

Best,
Gabriel Niculescu

> Dear Colleagues,
>
> We are inviting you to provide comments and hopefully join our new
> experimental
> proposal before submitting it to PAC 48.
>
> The proposal can be downloaded from:
>     https://urldefense.proofpoint.com/v2/url?u=http-3A__lichen.phys.uregina.ca_-7Ehuberg_pizero_PAC48-5Fpi0-5Fproposal.pdf&d=DwICaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=QxP5KTzkAiDxkNbQw9W17g&m=qho3NbSI7EBBkswZ3AGkQdLk9WPnOJoYXx5FFNauLV8&s=X9I-PYwiZz-_pOelaR9oNtYBdqYF7iBd9ST7rWaai08&e=
>
> In a short summary, this is standard hall C L/T measurement: standard
> HMS+SHMS
> configuration, standard unpolarized LH2 target and standard accelerator
> gradient (2.2 GeV/pass).  The proposed run time is 674 PAC hours.
> Technically,
> the experiment is as straightforward as an L/T-separation experiment ever
> gets.
>
> The unique aspect of this measurement is we aim to probe the nucleon
> structure
> at the backward-angle (t=t_max, u'=0) through exclusive process:
> 1H(e,e'p)pi0
> above the resonance region (W>2), x=0.36.  In this interaction picture,
> the
> recoil nucleon absorbs most of the induced momentum and is detected in the
> spectrometer at forward angles, while the scattered electron will be
> detected
> in other spectrometer (typically the HMS).  The backward pi0 (CM frame) is
> produced 180 degree opposite to the q-vector (central proton momentum)
> almost
> at rest, and is identified from the missing mass. You could call it a
> "knocking
> a proton out of a proton process".
>
> We aim to perform L/T separation at Q^2 range of 2-5 GeV^2, and two
> additional
> measured for check the W and Q^2 scaling.
>
> The objectives of the measurement are as follows:
>
> 1. Demonstrate the existence of a backward-angle (t=t_max) peak in the
> exclusive 1H(e,e'p)pi0 cross section above the resonance region.  The
> kinematics have been selected to facilitate comparison to forward angle
> exclusive pi0 data from E12-13-010, and the ideas behind the experiment
> have
> been presented previously at NPS Collaboration meetings.
>
> 2. Once the backward angle peaks are confirmed, the separated cross
> sections
> sigma_T and sigma_L at Q^2 =2, 3, 4 and 5 GeV^2 will be used to confirm
> the
> dominance of sigma_T over sigma_L, one of the predictions of the backward
> angle
> collinear factorization regime (Transition Distribution Amplitudes=TDA).
>
> 3. Perform a sigma_T~1/Q^n scaling test for 2<Q^2<6.25 GeV^2, which would
> further validate or refute the TDA factorization, and hopefully identify
> the
> scale at which the factorization regime is reached.
>
> If you have suggestions for improvement, please send them to us no later
> than
> June 17, and please include the relevant line number in your comment.
>
> We are looking forward to have your support for this proposal.
>
> Many thanks,
>
> Bill (Wenliang) Li, billee at jlab.org
> Justin Stevens, jrstevens at jlab.org
> Garth Huber, huberg at uregina.ca
>
> --
> Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2,
> Canada.
> tel: 1-306-585-4240. fax: 1-306-585-5659.
>
> _______________________________________________
> Hallc mailing list
> Hallc at jlab.org
> https://mailman.jlab.org/mailman/listinfo/hallc
>