Event shape analysis in diffractive DIS (past and future)

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Event shape analysis in diffractive DIS(past and
future)

• Alice Valkárová
• Charles University, Prague

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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
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fully aligned qq system
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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!
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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
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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!
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ZEUS paper from 2002. Using of LPS helped a lot.
Diffractive system is more spherical than in ee-
interactions, H1 results confirmed.
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MCs development
The significant improvement of RAPGAP generator
from 1997
Old comparison from the paper
HZTOOLs-RAPGAP 3.01
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MCs development
Ptlt1 GeV and Ptgt1 GeV
Old comparison from paper
New RAPGAP-HZTOOLs
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Distributions of pt2 in Mx intervals
New RAPGAP-HZTOOLs, more steep distributions
Fitted data in Mx intervals, slope is close to
?1/pt2
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Fraction of events with pt2gt1GeV2
New comparison
Old comparison (1997)
Not much improvement..
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Fraction of events with pt2gt3 GeV2
Old comparison (1997)
New comparison
Definitely not an improvement..
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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).

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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
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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