(a) Normalised energy loss as a function of the apparent momentum
p/|q| after the gas veto.
(b) Measured Cherenkov angle in the liquid radiator
as a function of the apparent momentum after the gas veto:
if four photons or less were observed
in the liquid radiator, the Cherenkov angle was set equal to zero.
The expectation curves for charge +-e particles for pions, protons and
heavy particles with masses of 10, 20, 45 and 65 GeV/c**2 are given, as well as
the dashed curves for charge +-2/3e particles with masses of 45 and 65
GeV/c**2.
Particles were selected if they had no associated photons in the gas RICH.
The rectangular areas in (a) indicate selections
- p > 5 GeV/c and anomalously high measured normalised
ionisation in the TPC (between 2 and 10).
Expected background from overlapping tracks, delta rays and Landau tail
is 0.5+-0.2 events for the whole data set.
- p > 15 GeV/c and anomalously low measured normalised
ionisation in the TPC (below the proton by at least 0.3 units).
Expected background from protons, kaons and pions
is 0.3+-0.3 events for the whole data set.
and that in (b) shows a selection of p > 15 GeV/c and a liquid RICH veto
(at most 4 photons in the lower part of the detector).
Expected background from normal particles with <4 photons
is 2+-1 events for the whole data set.
Identification efficiency :
Efficiency for pair-produced heavy particles
as a function of the mass of the particle for centre-of-mass energies of
130-136 (circles), 161 (rectangles), and 172 GeV (triangles) charge +-e
particles, interpolated with solid lines.
(b) Same quantities for charge +-2/3e particles.
Cross-section upper limits :
Cross-section upper limit at 95\% confidence level
for pair-produced heavy particles as a
function of the mass of the particle for centre-of-mass energies of
130-136 (circles),
161 (rectangles) and 172 (triangles) GeV, separately for particles of charge
+-e (upper plot) and +-2/3e (lower plot).
Mass limits on stable charginos :
Production cross-section for charginos with long
lifetimes at a centre-of-mass energy of 172 GeV for high and low
sneutrino masses and two
values of tan(beta), obtained with the SUSYGEN generator. The dark points
(lighter triangles) show
the predicted cross-sections for low (high) values of tan(beta) for values of
the MSSM
parameters M_1, M_2, mu, and the sneutrino mass m(snu) within the ranges
given in the text.
The lines connecting the open circles correspond to the combined experimental
upper limit
on the cross-section at 95% confidence level.
Stable charginos up to 84 (80) GeV/c**2 can be excluded for high (low)
sneutrino masses.
Mass limits on stable smu and stau :
Production cross-section for stable or long-lived left-handed (upper plot)
and right-handed (lower plot)
smuons or staus at a centre-of-mass energy of 172 GeV, calculated with SUSYGEN.
The lines connecting the open circles
indicate the combined experimental upper limit on the production cross-section
at 95% confidence level.
Masses between 45 GeV/c**2 and 68 (65) GeV/c**2 can be excluded for
left-handed (right-handed) stable smuons and staus.
REFERENCES :
Published in CERN-PPE/96-188, Phys.Lett. B396 (1997) 315.
The latest results on this analysis were presented by
P.Rebecchi,
Sparticles Search at LEP2 in DELPHI,
Cern seminar, 09/12/96.
Earlier presentations include:
J.Timmermans,
DELPHI Status Report
to the LEPC, 19/11/96
W.de Boer,
DELPHI Results at 161 GeV,
Cern seminar on LEP results, 08/10/96
