[Halld-physics] Reading Group Friday

Fri Aug 7 15:17:32 EDT 2015

Also see figure 7 in this
http://arxiv.org/pdf/hep-ex/9712027v1.pdf
for more J/psi photoproduction data.

Ryan

On Aug 7, 2015, at 1:44 PM, Eugene Chudakov <gen at jlab.org<mailto:gen at jlab.org>> wrote:

There is not much room for a large cross section times BR, because of
the existing measurements of J/psi photoproduction (Cornell), which
integrated the incoming photon energies. A 100MeV full width bump
produced at 1ub and decaying 100% to J/psi+p would produce 1000 times
more J/psi-s than observed.

A very high cross section for gamma+p-->P should be seen in the Compton scattering (Moskov is looking into it).

Eugene

On Fri, 7 Aug 2015, Curtis A. Meyer wrote:

I am still not sure I understand the numbers in the Karliner/Rosner paper, but they have peak
cross sections in the ub (micro barn) range, not the nb range for J/Psi production. This is probably
when I first started hearing about this, I assumed that the rates we could observe with nb or smaller
cross sections would make this incredibly hard to pull out. If a ub cross section is real, this would
stand out pretty clearly in our data.

Curtis
---------
Curtis A. Meyer MCS Associate Dean for Faculty and Graduate Affairs
Wean:    (412) 268-2745 Professor of Physics
Doherty: (412) 268-3090 Carnegie Mellon University
Fax:         (412) 681-0648 Pittsburgh, PA 15213
curtis.meyer at cmu.edu<mailto:curtis.meyer at cmu.edu> http://www.curtismeyer.com/

On Aug 7, 2015, at 12:31 PM, Eugene Chudakov <gen at jlab.org> wrote:

There is a collection of various links concerning J/psi
close-to-threshold photoproduction (see "meeting, talks") as well as
the older papers:

https://userweb.jlab.org/~gen/charm/

A few numbers:

The expected gamm+p-->J/psi+p cross section at 10 GeV is about 0.1nb.
The lowest Cornell point was about 0.5nb for <12 GeV. This led Brodsky
to speculate that there could be some anomaly.

We do not know the gamma+p-->P-->J/psi rate, but may assume, as the
starting point, the same ratio to non-resonance J/psi+p events as LHCB
had for the LB spectrum.  They had about 500 events per 15MeV bin. For
the incoming photon it would be an 80 MeV bin.

Assuming 0.1nb I estimated that one can get about 1600 events/bin in
Hall C (based on PR12-07-006 proposal)) and 100 events in Hall B
(based on PR12-12-001 proposal) for a 3-month run.

For GlueX at "low" intensity and the regular running (peak at 9 GeV
and 3mm hole) it would be about 2 ev/bin. Using the 5mm hole and 5
times more current would give about 20 ev/bin.

Eugene

------------------------------------------------------
Eugene Chudakov
https://userweb.jlab.org/~gen/
phone (757) 269 6959  fax (757) 269 6331
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave, STE 4,
Newport News, VA 23606 USA

On Fri, 7 Aug 2015, Richard Jones wrote:

Matt,

As this paper makes clear, Reinhard's idea of looking for this state in
formation mode with GlueX at 10GeV is well within reach. Of course the BR
to J/Psi,p might be miniscule but if so then why would this be the first
mode in which it has been seen? My comment to Reinhard last Friday that
searching for ccbar baryons in GlueX would be a long shot was incorrect.

-Richard Jones

On Wed, Jul 22, 2015 at 11:11 AM, Shepherd, Matthew <mashephe at indiana.edu>
wrote:

Hi all,

We decided to break momentarily from the photoproduction theme to read and
discuss this timely paper from LHCb on pentaquarks with hidden charm.

http://arxiv.org/abs/1507.03414

Let’s meet Friday at 3:30 in F326/7.  Focus primarily on the article
itself, which is the first 15 pages.

Please bring questions and topics for discussion!

Matt

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Department of Physics, Indiana University, Swain West 265
727 East Third Street, Bloomington, IN 47405

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