[Halld-physics] Reading Group Friday

[Justin Stevens]

The microbarn peak cross sections in the Rosner paper assume that the BR(P_c -> J/psi + p) = 1, but if this is not be the dominant decay mode the cross section can be much smaller.  This was illustrated in one of the other papers earlier this week http://arxiv.org/abs/1508.00339v1: see fig 3 vs fig 4.
-Justin

On Aug 7, 2015, at 12:59 PM, 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
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> 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
>>>> 
>>>> ---------------------------------------------------------------------
>>>> Matthew Shepherd, Associate Professor
>>>> Department of Physics, Indiana University, Swain West 265
>>>> 727 East Third Street, Bloomington, IN 47405
>>>> 
>>>> Office Phone:  +1 812 856 5808
>>>> 
>>>> 
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