Type I region
eR -> e chi1 (but delta-M
too small ... invisible)
eL -> chi2 e (delta-M
~ 10 GeV visible)
|
`--> slepR slep (delta-M can be small, but the slepton is "visible")
|
`--> chi1 slep (delta-M is too small, "invisible")
Type II region
eR -> chi2 e (delta-M
can be ~10 GeV but also very small i.e., e is "invisible")
|
`--> chi1 slep slep (2 additional leptons in the final state)
In both cases "standard" RR and LR selectron analyses fails because of extra leptons.
Two possible strategies can be envisaged to recover thesse regions by
using "existing" analyses:
a) try to apply existing selectron analyses which should have non zero
efficiency for some configurations of region I and II;
b) since the some neutralinos cross section in problematic region are
not negligible (i.e. xsect(neu2,neu2)>=1pb, xsect(neu2,neu3)>=1pb) use
existing/new neutralino "leptonic" selection.
In particular the neutralino multi-leptons analyses could help in some
of the unexcluded regions. For example the chi1-chi3 associated production
could help in region II:
neu3 -> sleptR lept
|
`-> neu2 lept
|
`-> neu1 lept lept
To conclude:
critical area
1 < tan(beta) <1.5
-35 < mu < -60 (GeV)
75 < M2 < 100 (GeV)
-50 < m0 < 0 (GeV)
possible solutions leptonic
neutralinos
efficiency from existing analyses
(typically LR selectron selection)
benefits from gap closing absolute snu limit
absolute selL limit (probably beyond
kinematic limit)
Probably the Higgs limit could help (but radiative correction are critical
and also the squark sector should be added).
No for Winter Conferences.
Coment from Jean-Francois: L3 already
published a lower limit on the slepton mass of 65.5 GeV, CERN-EP/99-128
(Frank should check this paper to see if what they do is correct)
M.Antonelli : Stops with lifetime
(short update)
The small dm stop analyses have been performed on full 1999 reprocessed
data sample. In the long lifetime topologies (stop hadron stable inside
ALEPH) no candidate comes from sqrt(s)>190 GeV data. Within the 411 pb-1
of 1998-1999 data, 1 event is selected (the same candidate of Fabio's analyses!)
while 0.5 are expected. In the intermediate lifetime selection (stop hadron
decaying inside ALEPH) 3 candidates are found in 1999 data for a total
of 4 candidates in all 1998-1999 data samples. Only 0.9 events are expected,
the excess due to cosmic ray events (2 of 4 candidates). With four candidate
is not
yet possible to set an stop mass limit not dependent on dm since a
corridor around dm ~2GeV is still open. Removing the cosmic ray candidates
(this should possible without no effect on the signal efficiency)
the corridor is finally closed and an absolute limit of 48GeV can be set.
To do to finalize the result:
P.Azzurri 1 : Chargino pairs searches
Paolo reports chargino searches results including full reprocessed1999
data sample. The E12 distribution included in the MC come from the reprocessed
random triggers too. The efficiency as a function of dm is found
to be pretty similar for all energies. All cuts are partially optimized
and suitably rescaled to sqrt{s}. One more candidate appear both in the
196 and in the 200 GeV data samples with respect to the not reprocessed
data. Generally speaking a not dramatic deficit is found in the low sfermion
mass selection (24 found, 33.9 exp). The chargino limits are anyhow close
to the kinematic limit for small M2 (any mu) and big abs(mu) (any M2).
The neutralino mass limit at large m0(=500GeV) vs. tan(beta) shows an improvement
of ~4 GeV with respect to the 189 GeV results, as shown at the LEPC.
P.Azzurri 2 : RPC gauginos at low
m0 with 1999 data and LSP mass scan
Paolo presents the update of the acoplanar leptons selection for neutralino
pair now designed to easily parametrise the efficiency, the efficiency,
the leptonic W-pair subtractable background and the candidate maps as a
function of the cuts on the lepton energies. The kinematics allow
to derive a maximum lepton pair energy from the minimum missing energy
carried away from the final invisible neutralinos. The selection features
an upper cut on this quantity according to the kinematics of the considered
signals. The efficiency is parametrised as a function of the mass difference
of the neutralino decay cascade that produces the two leptons. It is pretty
constant (>65%) for DM>5GeV, but quickly decreases in the low Delta_mass
regions. The effect of intermediate resonant sfermions(slepton,sneutrino)
in the cascade decays was also studied in detail. The efficiency has been
finally parametrised as a function of the neutralino DeltaM parameter only.
Such parametrizations allows to use an automatic procedure to scan
the low m0 mass region. The procedure also implements the 1999 low m0 chargino
(2-body and 3-body) searches and 1999 slepton searches. The
neutralino hadronic decays still need
to be added. For that an automatic procedure is not feasible and the standard
manual scan will be used.
J.Vollinga : Study of stau mixing in
chargino searches
Jens presented the study of the impact of the stau mixing on
the chargino exclusions at low m0. The optimal combination of existing
selection has been identified as a function of dm, leptonic branching ratio
and tau lepton production probability. The effect of stau mixing angles
up to 45 degrees has been studied both in the plane M@ vs. mu and m(chi)
vs. m(snu) for various combination of the other free parameters.
As a general observation one could say that the mixing becames not
negligible around >30 degrees. Nevertheless the absolute gaugino mass
limit is not affected by the stau mixing. The study must be extended for
mixing angles greater than 45 degrees and may be reported in a note.
Comment for Jean-Francois: the stau mixing
angle should go from 0-90 degrees ant not from 0-45.
Comments from Gerri: It is not clear why
he doesn't find the corridor for Mstau~Mchi0
where the chargino diminant decay is cha -> stau
nu -> chi tau nu ("invisible"
for Mstau-Mchi < 4 GeV) found by Gerri in the mSUGRA scan.
C.Booth : Sleptons with lifetime
Chris presents a short update of the livng slepton searches. The analysis
has been performed on the full 1999 reprocessed data and features a bigger
MC background samples. No change with respect to not reprocessed data (1
candidate vs. 0.57 events expected). The systematics have also been
checked. The only relevant contribution comes from the efficiency parametrization
(3% to 5% relative). This have actually a small effect on the limits. The
other slepton analyses LEPC results have been added. It turns out an absolute
95% C.L. limit on the stau mass of 72 GeV/c^2. 189 GeV data are not yet
included in Chris' selection but probably it is not worth to do that since
the improvement will be really small (~100keV).
F.Cerutti : Stable sleptons
Fabio reports the situation of his analysis with respect to the 1999
reprocessed data. The tracking data quality (very important for the selection)
is clearly improved with the perpocessing as the positive vs. negative
muon momentum unbalance distribution shows. Generally speaking the tracking
quality seems better in the data than in MC. The data/MC dE/dx agreement
is not perfect but this has no effect with respect to the selection.
Taking into account all 98-99 data sample, 1 candidate
is observed
while 1.1 background event is expected
(mainly from double radiative dimuon events). The limit on m(stauR)
is about 94 GeV to be compared with 89 GeV, the 1998 result.
Fabio Cerutti + all: Plans for Winter Conferences
The Thursday meeting devoted to Winter Conferences is on 17-18/2.
In order to cope with this deadline all SUSY results we want to submit
have to be presented at the STF on 16/2. If something is ready before a
STF on 9/2 could be orgenised.
General statement: short update note for all standard analyses (like
189 GeV sfermion paper). More detailed note for all new stuff as stable
squarks, stau mixing, single sneutrino. Probably something from Nicola
and Richard will be ready for the 2/3 (deadline for Moriond) in their new
subjet (AMSB). Details on meeting dates + deadlines an poeple responsible
fot the different confnotes are available on:
List of SUSYTF + LEPSUSYwg + ALEPH Thursday meetings in preparation of the winter conferences List of SUSYTF Winter Conference Notes with Editors names
G.Ganis : LEPSUSYwg combination
All this stuff may fit in a global interpretation superpaper
that would be optimal in order to minimize the efforts since manpower is
going to decrease. The timescale may be end of 2000 for SUSY analyses and
something more to include higgs results.
J.F.Grivaz : AOB = Sgoldstino searches
Jean-Francois presents the idea for a new SUSY searches. The
target of such a selection is the sgoldstino S the positive Rparity partner
of the goldstino. Want to learn more? ---> Perazzi,
Ridolfi and Zwirner hep-ph/0001025 (DFPD-99/TH/55). The production
processes are e+e- --> gamma S or e+e- -->
Z S. The S likes to decay in gluon pairs.
Thus the more convenient topology to look for would be gamma g g. Even
if tagging this topology may not be easy, the subject looks interesting.
