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Event shape analysis in diffractive DIS (past and future)

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Title: Event shape analysis in diffractive DIS (past and future)


1
Event shape analysis in diffractive DIS(past and
future)
  • Alice Valkárová
  • Charles University, Prague

2
Definition of thrust
For each event obtain the information
on Orientation w.r.t. photon pomeron axis Shape
given by thrust T
Thrust finds the direction in CMS along which
the energy flow is maximal
½ lt T lt
1
fully aligned qq system
3
Motivation
The thrust is the possible tool to distinguish
between two-jet (qq) and three-jet (qqg)
configurations. It was very useful also in the
case of gluon discovery. The important quantity
is also the pt of the thrust axis w.r.t. the
interaction axis
?
pomeron
Thrust axis pt was not measured by ZEUS!
4
The past
H1 publication Thrust Jet Analysis of
Deep-Inelastic Large-Rapidity-Gap Events C.Adloff
et al.,Eur.Phys.J. C1 (1998) 495-507
1994 data with 2 pb-1 using rapidity gap method
ZEUS publication Event Shape Analysis of DIS
Events with Large Rapidity Gap at HERA J.Breitweg
et al.,Phys.Lett. B 421 (1998),368
1994 data with 2.6 pb-1 using of Mx metod
ZEUS publication Properties of hadronic final
states in diffractive DIS at HERA S.Chekanov et
al.,Phys.Rev.D65,052001 (2002)
1997 data with 13.8 pb-1 using LPS spectrometer
5
ep diffraction ee-
Thrust from H1 paper 1998
Thrust in ep diffraction was found to be smaller
than in ee- thus indicating larger fraction of
higher parton multiplicities in ep than in ee-
It was not confirmed by ZEUS paper from 1998!
6
ZEUS paper from 2002. Using of LPS helped a lot.
Diffractive system is more spherical than in ee-
interactions, H1 results confirmed.
7
MCs development
The significant improvement of RAPGAP generator
from 1997
Old comparison from the paper
HZTOOLs-RAPGAP 3.01
8
MCs development
Ptlt1 GeV and Ptgt1 GeV
Old comparison from paper
New RAPGAP-HZTOOLs
9
Distributions of pt2 in Mx intervals
New RAPGAP-HZTOOLs, more steep distributions
Fitted data in Mx intervals, slope is close to
?1/pt2
10
Fraction of events with pt2gt1GeV2
New comparison
Old comparison (1997)
Not much improvement..
11
Fraction of events with pt2gt3 GeV2
Old comparison (1997)
New comparison
Definitely not an improvement..
12
Summary proposal
  • with new RAPGAP thrust data from 1994 are
  • described better than previously
  • distributions of pt2 of thrust axis w.r.t.axis
    of
  • interaction are still poorly described there
    is
  • not enough of events with higher pt in MC
  • use new data (lumi 50 times larger )with the
  • information from VFPS
  • (non-diffractive background suppressed) to
    analyze
  • pt2 distributions much more thoroughly,
  • (in dependence on W and other variables).

13
RAPGAP direct and resolved, ntuples used for
Kamils jet analysis
Non-diffractive, Q2gt2 GeV2
Ptgt5 GeV, -3.lt?lt0.
Azimuthal angles of first and second jet in ?p CMS
14
HZTOOLs RAPGAP 3.1 BGF
Diffraction
350 k events
Analysis of F.P.Schilling 4ltQ2lt80 GeV2, CDF cone,
ptgt4GeV -3.lt?lt0. in HCMS
Jets on hadron level
250 kevents
200 kevents
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