[Jef] [EXTERNAL] Re: QNP talk of Rafel Escribano

[Shepherd, Matthew]

> On Sep 9, 2022, at 10:59 AM, Igal Jaegle <ijaegle at jlab.org> wrote:
> 
> There was an interesting talk this morning, https://indico.jlab.org/event/344/contributions/10404/attachments/8449/12080/QNP2022_REscribano.pdf. 


An note about sensitivity and BESIII:  that talk that Igal sent references publications that use a sample of 1.3 x 10^9 J/psi decays from BESIII.

I noticed when I was preparing a recent talk that BESIII has just started publishing papers that use the full sample of 10^10 J/psi events.  This should push useable data up by an order of magnitude from those publications.

With 10^10 J/psi one has just from the radiative decay alone about 10^7 eta and 5 x 10^7 eta', each of which could be tagged by the mono energetic photon.  (There are other channels like phi + eta and phi + eta' that are of the same order could maybe get some factors of 2-3 in some modes.)  

Looks like this is still not quite at the KLOE2 level for eta:  B. Cao [KLOE-2], PoS EPS-HEP2021 (2022) 409 notes 3 x 10^8 eta's from phi decay.

In addition, BESIII also has 2.7 x 10^9 psi' decays which provide interesting opportunities with eta due to these decays:

psi' -> J/psi eta (3%)
psi' -> pi+ pi- J/psi; J/psi -> gamma (eta or eta')

The first provides pretty pure sample of almost 10^8 eta decays.. but very different kinematics from J/psi radiative -- these etas are nearly at rest in the lab.  Starting from the psi' is nice because you can tag the eta by using the J/psi or the di-pion + photon system.  You need these high-purity hadron tags to suppress QED backgrounds in the e+/e- environment if you want to do searches for things like eta(') -> invisible.

I'm not sure how these yields compare with JEF anticipated yields.  The experimental environments and detectors are also different so one needs to consider sensitivity for certain kinds of measurements.  And, as has been often discussed, the eta kinematics plays an important part, especially for high-multiplicity neutral decays.

I'm diverging a bit from the initial note... but this whole global picture must be considered somehow when we discuss potential extensions of JEF to realize some particular sensitivity.

Cheers and have a good weekend!

Matt

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