1. Event shape analysis in diffractive DIS (past and future)
Alice Valkárová
Charles University, Prague
1/2/2019
Diffractive meeting, Antwerpen 2005

2. Diffractive meeting, Antwerpen 2005
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 < T <
isotropic
fully aligned
qq system
1/2/2019
Diffractive meeting, Antwerpen 2005

3. Diffractive meeting, Antwerpen 2005
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 pt γ
pomeron
Thrust axis pt was not measured
by ZEUS!
1/2/2019
Diffractive meeting, Antwerpen 2005

4. Diffractive meeting, Antwerpen 2005
The past
H1 publication:
Thrust Jet Analysis of Deep-Inelastic Large-Rapidity-Gap Events
C.Adloff et al.,Eur.Phys.J. C1 (1998)
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, (2002)
1997 data with 13.8 pb-1 using LPS spectrometer
1/2/2019
Diffractive meeting, Antwerpen 2005

5. Diffractive meeting, Antwerpen 2005
ep diffraction & e+e-
Thrust from H1 paper 1998
Thrust in ep diffraction was
found to be smaller than in
e+e- thus
indicating larger fraction
of higher parton multiplicities
in ep than in e+e-
It was not confirmed by ZEUS
paper from 1998!
1/2/2019
Diffractive meeting, Antwerpen 2005

6. Diffractive meeting, Antwerpen 2005
ZEUS paper from Using of LPS helped a lot….
Diffractive system is more spherical than in e+e- interactions,
H1 results confirmed.
1/2/2019
Diffractive meeting, Antwerpen 2005

7. Diffractive meeting, Antwerpen 2005
MC’s development
The significant improvement of RAPGAP generator from 1997
Old comparison from the paper
HZTOOLs-RAPGAP 3.01
1/2/2019
Diffractive meeting, Antwerpen 2005

8. Diffractive meeting, Antwerpen 2005
MC’s development
Pt<1 GeV and Pt>1 GeV
Old comparison from paper
New RAPGAP-HZTOOLs
1/2/2019
Diffractive meeting, Antwerpen 2005

9. Distributions of pt2 in Mx intervals
New RAPGAP-HZTOOLs,
more steep distributions
Fitted data in Mx intervals,
slope is close to ∝1/pt2
1/2/2019
Diffractive meeting, Antwerpen 2005

10. Fraction of events with pt2>1GeV2
New comparison
Old comparison (1997)
Not much improvement……..
1/2/2019
Diffractive meeting, Antwerpen 2005

11. Fraction of events with pt2>3 GeV2
Old comparison (1997)
New comparison
Definitely not an improvement..
1/2/2019
Diffractive meeting, Antwerpen 2005

12. Diffractive meeting, Antwerpen 2005
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).
1/2/2019
Diffractive meeting, Antwerpen 2005

13. Diffractive meeting, Antwerpen 2005
RAPGAP direct and resolved, ntuples used for Kamil’s jet analysis
Pt>5 GeV,
-3.<η<0.
Non-diffractive, Q2>2 GeV2
Azimuthal angles of first and second jet in γp CMS
1/2/2019
Diffractive meeting, Antwerpen 2005

14. Diffractive meeting, Antwerpen 2005
HZTOOLs – RAPGAP 3.1 BGF
350 k events
Diffraction
Analysis of F.P.Schilling
4<Q2<80 GeV2,
CDF cone, pt>4GeV
-3.<η<0. in HCMS
Jets on hadron level
250 kevents
200 kevents
1/2/2019
Diffractive meeting, Antwerpen 2005