Minutes of SUSY meeting Wednesday 24 May 2000
Second look at y2k data
General comments: L~35pb-1 at <Elep>~205. GeV.
Bkg extrapolated from 202 MC.
Rpv topologies UDD (D.Fouchezs for D. Hutchcroft):
Luminosity analyzed at Ecm=200 -> 208 GeV: 34.8 pb-1 for UDD
( 8 Topologies)
No excess found. Slight discrepancy in the UDD "Multi-jets + lepton"
topology where 6 candidates are observed for a background of 3.4 expected.
At 202 GeV in 99 we had 9 candidates with a bkg of 3.85. They'll keep an
eye on this channel.
Some shape variables have been checked at the preselection level (like
Y56) .... good agreement DT-MC.
GMSB topologies with photons (G.Taylor):
Lose preselection applied (class 2) provisionally. E12 veto
inefficiency checked ~5% for nng events.
Results:
DT MC
single g + Emiss
82 84
2g + Emiss
3
5
GMSB 2g
0 0.5
MSSM 2g
1 1.5
QED 2g
215 236
Good agreement data SM bkg also at the level of shapes (missing mass,
energy and angular distribution).
GMSB stable sleptons + check on electron ID (F.Cerutti):
About 35pb-1 of y2k data analyzed.
First look at P scale, Acollinearity and dE/dx on non-radiative dimuons:
agreement DT MC quite good. The distribution of |P1-P2|/s(P)
is slightly larger in the Data. Strange shape for the distribution of
P(m+)/Ebeam ... to be followed.
Expected bkg is 0.15, 0 candidates found.
Check of RT and RL variables used in electron ID: Selected Bhabhas
and applied the same cut used in stau analysis (100>RT>-2.4 and 3>RL>-2.4).
Electron ID checked in bins of P and cos(theta). After the cuts 5<P<90
GeV and |cos(q)|<0.9 the efficiencies are
DT=90.6% and MC=89.2%. In the central region of the detector (|cos(theta)|<0.85)
the agreement is always better than 2 %. In forward region discrepancies
up to 6% found. To be cross checked with other physics groups. .
GMSB long lived sleptons (C.Booth):
About 24pb-1 of y2k data analyzed. Last year analysis applied. No candidates
found in the data. Marginal improvement on the stau mass exclusion (less
than 1 GeV).
MSSM squarks (M.Antonelli):
About 22pb-1 of y2k data analyzed. Different variables (Mhad/Elep, Mtot/Elep,
Thrust, Acopt, Eletpon-lead/Elep, b-tag) checked on preselected events
(Mainly qq(g) and WW); good agreement found
for all the variables but the b-tag which looks bad.
Results:
MC DT
stop -> c chi
1.2 2
(1 low and 1 high dM)
stop -> b l snu
0.4 0
sbot -> b chi
0.5 1
(the same candidate selected by the stop -> charm chi low-dM analysis)
MSSM charginos (P.Azzurri):
About 22pb-1 of y2k data analyzed.
For the W* BRs analyses 0 candidates for an expected bkg of 1.1; for
the generic BR analyses 2 candidates (selected by acoplanar-lepton lepton-tau
topology) with an expected bkg of 3.2 events. Some selection variables
checked (DT MC comparison) at the preselection level.
MSSM neutralinos (F.Gianotti):
About 22pb-1 of y2k data analyzed.
Neutralinos. AJ topologies looked at:
delta-M<15 GeV 0 candidates (bkg 0.03),
delta-M<25 GeV 0 candidates (bkg 0.05),
delta-M<45 GeV 0 candidates (0.2 bkg),
Wmiss>110 GeV 5 candidates (bkg 2.3 with PYTHIA .... should
be about 4.6 with G4F).
MSSM sleptons (B.Clerbaux):
A large number of checks has been performed on 98-99 data (~411 pb-1) by
using WW-> lv lv sample. This sample is obtained by removing in the stau
analysis the Mvis cut (Mvis<80 GeV) and the veto on the lepton energy
(Plept-max<23 GeV). A sample of 370 events (MC=368.6) is obtained in
189-202 GeV data.
Tau-ID (used in the lepton VETO cut) is checked:
t-ID
DT MC
Electron 290
292.7
Muon 274
269.7
Hadrons 176
174.8
With this check the lepton ID used in the momentum VETO cut is checked
at the 5% level. Some discrepancy in the stau mass distribution is observed
in the region between 0 and 0.4 GeV, probably due to electrons with a radiated
photons.
A comparison between the stau high-dM analysis ant the WW-> ttnn
and H+H- -> tntn has been performed on 2000
data. The results are:
DT
MC
stau
7
3.5
H
4
5.2
W
6
not given
The stau and the W analysis have 5 events in common. The H analysis
have only 2 events in common with W and 1 in common with stau. Two of the
H candidates have energy deposits at low polar angle (NO E12 cut
is applied in this analysis); they look like llgg
events. Some of the stau events are not accepted by W or H analyses because
of the Mjet cut (not very well reproduced by MC !). In the stau selection
there are two events with a 2 tracks with the same sign. It has to be understood
if this happens also in the signal topologies otherwise this events should
be rejected. One event selected by both W and H but not by the stau, has
a very low theta track (cos(q) below 0.95),
it looks like a Zg* event (not a very good candidate).
About 35pb-1 of y2k data analyzed.
Results:
MC
DT
Selectron
6.2
7
Smuon
6.3
12
Staus
4.9
11
In the reference point Mstau=85 Mchi=20 we have DT=7 MC=3.5.
Report on the "stau mixing impact on gauginos limits"
(J.Vollinga):
Good pregress on this work has been showed. There is still a small corridor
to close which happens to be at large tgb when
the chargino decays into stau n and the stau
decays to ct with very small dM. To close this
gap two new analyses should be developped:
1) stable or long lived staus for charginos decay when dM is very small
2) single stau (soft or long lived) for the topology cc'
-> stau tc -> c c stau (stau)
Some technical problems hav been encountered in the long lived staus
simulation. A preliminary version of the note can be found here.
Report on the "Absoluts slepton mass limit"
(H.Bluemenshein):
Both problematic regions I and II have been addressed by using dedicated
analyses.
Region I: cascades of the cc"
decays (s~1.3 pb) have been used. The final
state consists of two leptons (one can be very soft).
Region II: snu snu -> cc' and cc''
production have been used. The final state consists of two leptons.
From a first scan it seems that the two problematic regions have been
excluded. A lower limit on the slepton mass of about 70 GeV is derived.
A fine scan and a note are needed to send the results to summer conferences.
Report on the "Neutralino cascade decyas in GMSB"
(E.Buhova):
The reoptimization of Michael analyses is going on. First results are expected
at the nexts SUSYTF.
Submitted by: Fabio Cerutti