Old Physics Analysis Old Physics Analysis

This page is intended to provide access to the various physics analysis topics that are being pursued with the GlueX detector. At this stage these typically consist of Monte Carlo studies which help demonstrate the feasibility of a particular analysis.

Ongoing Analyses

• Grid issues, reconstruction, and PWA of pi+pi+pi-n (Jake Bennett)

• Particle ID and tracking issues using K+K-p and pi+pi-p (Kei Moriya)

• Analysis of omega pi+ pi- (Igor Senderovich)

• Kinematic fitting in b1pi (Will Levine)

• Simulations of cascade baryons (Nathan Sparks)

• Analysis of gamma p --> eta pi0 p (Irina Semenova and Andrei Semenov)

Completed Analyses

• Analysis of gamma p --> eta pi0 p (Blake Leverington)
  • University of Regina PhD Thesis (see chapter 7)

Physics at the Information Frontier Center

• Collaborative Analysis Toolkit Wiki

Expected Statistics for GlueX

• The expected statistics for GlueX in 1 year of running will depend on several crucial factors, summarized below.
• Initial studies for the expected data rates for GlueX were done in
  • GlueX PAC30 Documentation
  • Potential GlueX Physics During the First Two Years of 12 GeV Running
  • Talk:The First Two Years of GlueX Physics
• The experimental data input for the cross sections at 9 GeV come from SLAC, namely
  • H. H. Bingham et al. (SLAC) Phys. Rev. D8, 1277
  • J. Ballam et al. (SLAC) Phys. Rev. D7, 3150
  • and references therein
• SLAC photoproduction results

$\sigma _{{tot}}$	124.0$\pm$2.5 $\mu$b
$p\pi ^{{+}}\pi ^{{-}}$	14.7 $\pm$0.6 $\mu$b
$pK^{{+}}K^{{-}}$	0.58 $\pm$0.05 $\mu$b
$n2\pi ^{{+}}\pi ^{{-}}$	3.2 $\pm$0.7 $\mu$b

• Basic formula to calculate expected events: $N_{{raw}}=\sigma \times N_{{t}}\times N_{{\gamma }}\times T$ where
  • $N_{{raw}}$: expected raw events
  • $\sigma$: cross section for wanted reaction
  • $N_{{t}}$: density of target
  • $N_{{\gamma }}$: number of photons/s
  • $T$: integrated time
• The total number of events that we actually detect is then $n=N_{{raw}}\times \epsilon \times BR$ where
  • $\epsilon$: expected construction efficiency for this channel
  • $BR$: the branching fraction of the particular decay to this channel

so that $n=\sigma \times N_{{t}}\times N_{{\gamma }}\times T\times \epsilon \times BR$, and the number of events is the product of 6 factors.

• The target density, $N_{{t}}$ is the easiest to determine. With a 30cm $LH_{{2}}$ target, the density is $1.26b^{{-1}}$
• The photon rate is expected to start at $10^{{7}}\gamma /s$, with a gradual increase to the maximum of $10^{{8}}\gamma /s$
• For the integrated time $T$, we assume, as in the previous studies listed above, that we run for 1 year, of which 6 months is datataking, with 1/3 efficiency (effectively 2 months out of the first year), which gives us $5\times 10^{{6}}$ s (this efficiency also takes into account the tagging ratio)
• The most difficult estimates are the factors of $\sigma$ (the cross section), $\epsilon$ (the efficiency of reconstruction), and $BR$ (the branching ratio), all of which are dependent on the specific channel of interest. Here we take the channel $\pi \pi \pi (n)$, since this is one of the prime channels of interest, and Monte Carlo studies have been done on this channel. According to the SLAC data above, the cross section for $n2\pi ^{{+}}\pi ^{{-}}$ is $\sigma =3.2\mu b$, of which an unknown fraction will be our signal of interest, the $\pi _{{1}}(1600)$. Current (2011) efficiency studies by Jake Bennett at IU show that the reconstruction efficiency in the mass region of interest is around $20\%$, with hopefully an increase as the kinematic fitter is further developed. Taking $BR=1$, we come to our final estimate of

$n=3.2[\mu b]\times 1.26[b^{{-1}}]\times 10^{{7}}[s^{{-1}}]\times 5\times 10^{{6}}[s]\times 0.20\times 1=400M$ events.

• This number can be contrasted with the estimates given in the above references, for example, $p\pi ^{{+}}\pi ^{{-}}$ assuming $\sigma =20\mu b$ and $\epsilon =0.75$ and the same flux and integrated time as above gives $940M$ events in the 1st year.
• Also to be contrasted is the number of events in other analyses. These include:
  • Nozar et al. (CLAS) photoproduction of $\pi ^{{+}}\pi ^{{+}}\pi ^{{-}}(n)$: 83k events for PWA
  • Dzierba et al. (E852-IU) pionproduction of $\pi ^{{-}}\pi ^{{-}}\pi ^{{+}}p$: 2.6M events
  • Alekseev (COMPASS) pionproduction of $\pi ^{{-}}\pi ^{{-}}\pi ^{{+}}p$: 420k events
• In conclusion, even with the relatively pessimistic numbers of $T=$ 2 months effective running, $\epsilon =0.20$, $N_{{\gamma }}=10^{{7}}\gamma /s$, GlueX should accumulate on the order of several hundred million events in the channels of interest, which is at least 2-3 orders of magnitude higher than other experiments.

Documentation/Studies

• Potential GlueX Physics During the First Two Years of 12 GeV Running
• Talk:The First Two Years of GlueX Physics
• Simulations of Exotic Mesons in GlueX
• Calorimeter physics simulations and reconstruction for the Calorimetry Review (GlueX Portal)
• PrimEx at GlueX
• Photoproduction & Lattice QCD
• A Summary of Hybrid Masses and Decays
• Radiation length scans
• b1pi with GlueX Monte Carlo

Software Analysis Tools

1. JANA-based GlueX Analysis Framework:
   1. GlueX Analysis Library: JANA-based, details on GlueX reconstruction classes, event selection, etc.
2. Partial Wave Analysis Tutorials
   1. pwa-ruby wiki : An installation and usage howto for the ruby-pwa code. The site also includes a fully worked out simple example.
3. The qft++ code
   1. The qft++ code was developed by Mike Williams at Carnegie Mellon University to facilitate analytic calculation of tree-level diagrams for partial wave analysis.
   2. Details can be found on the qft++ Website.
   3. A paper has also been submitted to Comp. Phys. Comm. (2008). arXiv:0805.2956
4. Software Packages
   1. The Ruby-Minuit Package Ruby-Minuit is a Ruby binding to CERNLIB's MINUIT package (which is written in FORTRAN). It provides access to MINUIT's powerfull minimization routines from the infinitely flexible Ruby language.
   2. The qft++ package was written (in C++) to numerically calculate quantum field theory expressions. The API was designed such that the code strongly resembles the hand-written expressions.
5. Maximum Likelihood Fitting.
   1. A short note on maximum Likelihood Fitting.
6. A generalized background subtraction method was developed to facilitate the baryon PWA done at CMU. This has been published as JINST 4 P10003, (2009), arXiv:0809.2948.

Useful Articles

• Article Archive from Curtis
• Reconstruction References

Meetings

Physics Working Group Meetings

BCAL Reconstruction Work

Useful Links

• Institute for Nuclear Theory (INT) workshop in November 2009
• Workshop on photon-hadron physics with the GlueX detector
• JLab PWA wiki