-
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
E. Merle,
M.-N. Minard,
J.-Y. Nief, [......],
J.M. Nachtman,
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: An improved measurement of the forward-backward asymmetry in decays is presented, based on a sample of 4.1 million hadronic Z decays collected by ALEPH between 1991 and 1995. Data are analysed as a function of polar angle of the event axis and b purity. The event tagging efficiency and mean b-jet hemisphere charge are measured directly from data. From the measured forward-backward jet charge asymmetry, the b quark asymmetry at is determined to be: AbFB=0.1017±0.0038(stat.)±0.0032(syst.). In the context of the Standard Model this corresponds to a value of the effective weak mixing angle of sin2θWeff=0.23109±0.00096.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
E. Merle,
M.-N. Minard,
J.-Y. Nief, [......],
J.M. Nachtman,
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The flavour changing neutral current decay b→sγ has been detected in hadronic Z decays collected by ALEPH at LEP. The signal is isolated in lifetime-tagged events by the presence of a hard photon associated with a system of high momentum and high rapidity hadrons. The background processes are normalised from the data themselves. The inclusive branching ratio is measured to beconsistent with the Standard Model expectation via penguin processes.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
E. Merle,
M.-N. Minard,
J.-Y. Nief, [......],
J.M. Nachtman,
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Starting from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP, 404 charged and neutral B mesons are fully reconstructed and used to look for resonant structure in the Bπ system. An excess of events is observed above the expected background in the Bπ mass spectrum at a mass ≈5.7 GeV/c2, consistent with the production and decay to B(∗)π of the B∗∗ states predicted by Heavy Quark Symmetry (HQS). In the framework of HQS, it is found that the mass of the state is MeV/c2 and the relative production rate of the B∗∗ system is . In the same sample of B mesons, significant Bπ± charge-flavour correlations are observed, which may prove important for tagging the initial B state in future CP violation studies.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
S. Jezequel,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
J.-Y. Nief, [......],
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
J.M. Yamartino,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 10.65 pb−1 collected with the ALEPH detector at a mean centre-of-mass energy of 172.09 GeV. The invariant mass distribution of simulated events are fitted to the experimental distributions and the following W masses are obtained:The statistical errors are the expected errors for Monte Carlo samples of the same integrated luminosity as the data. The combination of these three measurements gives:
Physics Letters B 03/2013; · 3.95 Impact Factor
-
D. Buskulic,
I. De Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
P. Odier,
B. Pietrzyk, [......],
M. Schmitt,
I.J. Scott,
V. Sharma,
J.D. Turk,
A.M. Walsh,
Sau Lan Wu,
X. Wu,
J.M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Searches for supersymmetric particles produced in e+e− collisions at centre-of-mass energies of 130 and 136 GeV have been performed in a data sample of 5.7 pb−1 collected in the autumn of 1995 by the ALEPH detector at LEP. No candidate events were found, allowing limits to be set on the masses and production cross-sections of scalar leptons, scalar tops, charginos and neutralinos. The domains previously excluded at LEP1 are substantially extended. For instance, masses of gaugino-like charginos smaller than 67.8 GeV/c2 are excluded at the 95% C.L. for scalar neutrino masses larger than 200 GeV/c2.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
D. Buskulic,
I. De Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
J.-Y. Nief,
P. Odier, [......],
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
A.M. Walsh,
Sau Lan Wu,
X. Wu,
J.M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: A search for pair production of new heavy leptons has been performed assuming different scenarios for the mixing of the new particles with Standard Model leptons. No candidate events were found in a data sample corresponding to an integrated luminosity of 5.6 pb−1 collected by the ALEPH detector at centre-of-mass energies of 130 and 136 GeV. New limits on production cross-sections and on masses of sequential leptons were obtained which significantly extend the mass regions excluded at LEP1. For instance, charged heavy leptons with masses below 63.5 GeV/c2 are excluded at 95% C.L. for mass differences to the associated neutral lepton of more than 7 GeV/c2.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
D. Buskulic,
I. De Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
P. Odier,
B. Pietrzyk, [......],
Y. Saadi,
M. Schmitt,
I.J. Scott,
V. Sharma,
A.M. Walsh,
Sau Lan Wu,
X. Wu,
J.M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Searches for charginos and neutralinos produced in e+e− collisions at centre-of-mass energies of 130 and 136 GeV have been performed under the assumptions that R-parity is not conserved, that the dominant R-parity violating coupling involves only leptonic fields, and that the lifetime of the lightest supersymmetric particle can be neglected. In the 5.7 pb−1 data sample collected by ALEPH, no candidate events were found. As a result, chargino and neutralino masses and couplings are constrained and the domains previously excluded at LEP1 are extended.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
S. Jezequel,
J.-P. Lees,
A. Lucotte,
F. Martin,
E. Merle, [......],
J.M. Nachtman,
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV, corresponding to a total integrated luminosity of about 80 pb−1. The measured distributions are in agreement with Standard Model predictions, leading to constraints on WWγ gauge coupling parameters Δκγ and λγ. The results from the fit to the cross sections and to the energy and angular distributions of the photons are: Δκγ=0.05+1.15−1.10(stat)±0.25(syst), λγ=−0.05+1.55−1.45(stat)±0.30(syst).
Physics Letters B 03/2013; · 3.95 Impact Factor
-
R. Barate,
D. Decamp,
P. Ghez,
C. Goy,
S. Jezequel,
J.-P. Lees,
F. Martin,
E. Merle,
M.-N. Minard,
B. Pietrzyk, [......],
J.M. Nachtman,
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 57 pb−1 collected with the ALEPH detector in 1997 at a centre-of-mass energy of 183 GeV. The invariant mass distributions of reweighted Monte Carlo events are fitted separately to the experimental distributions in the and all channels to give the following W masses:where the theory error represents the possible effects of final state interactions. The combination of these two measurements, including the LEP energy calibration uncertainty, gives
Physics Letters B 03/2013; · 3.95 Impact Factor
-
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
S. Jezequel,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
J.-Y. Nief, [......],
J. Nielsen,
W. Orejudos,
Y.B. Pan,
Y. Saadi,
I.J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
J.M. Yamartino,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The triple gauge-boson couplings, αWΦ, αW and αBΦ, have been measured using 34 semileptonically and 54 hadronically decaying W+W− candidate events. The events were selected in the data recorded during 1996 with the ALEPH detector at 172 GeV, corresponding to an integrated luminosity of 10.65 pb−1. The triple gauge-boson couplings have been measured using optimal observables constructed from kinematic information of W+W− events. The results are in agreement with the Standard Model expectation.
Physics Letters B 03/2013; · 3.95 Impact Factor
-
D. Buskulic,
I. De Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
P. Odier,
B. Pietrzyk, [......],
Y. Saadi,
M. Schmitt,
I.J. Scott,
V. Sharma,
A.M. Walsh,
Sau Lan Wu,
X. Wu,
J.M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The B0 - B̄0 average mixing parameter and b forward-backward asymmetry AFB0(b) are measured from a sample of about 4 200 000 Z → qq̄ events recorded with the ALEPH detector at LEP in the years 1990–1995. High transverse momentum electrons and muons produced in b semileptonic decays provide the tag of the quark flavour and of its charge.The average mixing parameter and the pole b asymmetry are measured to be = 0.1246 ± 0.0051stat ± 0.0052syst, AFB0(b) = 0.1008 ± 0.0043stat ± 0.0028syst. The value of sin2θweff = 0.23198 ± 0.00092 is extracted from the asymmetry measurement.
Physics Letters B 12/2012; · 3.95 Impact Factor
-
Damir Buskulic,
I De Bonis,
D Décamp,
P Ghez,
C Goy,
J P Lees,
A Lucotte,
M N Minard,
J Y Nief,
P Odier, [......],
W Orejudos,
Y B Pan,
Y Saadi,
I J Scott,
A M Walsh,
Wu Sau Lan,
X Wu,
J M Yamartino,
M Zheng,
G Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Using data obtained with the ALEPH detector at the Z resonance, a measure based on transverse momentum is shown to exhibit a correlation between the two halves of a hadronic event which cannot be explained by energy-momentum conservation, flavour conservation, the imposition of an event axis or imperfect event reconstruction. Two possible explanations based on Monte Carlo models are examined: a) ARIADNE, with the correlation forming early in the parton shower and with the transition from partons to hadrons playing only a minor part; b) JETSET, with the correlation forming at the fragmentation stage. A correlation technique based on a jet cluster analysis is used to make a comparison of the models with the data. It is concluded that both non-perturbative and perturbative effects make important contributions to the observed correlation.
Zeitschrift für Physik C 12/2012; 73(3):421.
-
ALEPH Collaboration,
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
J.-Y. Nief, [......],
J. Nielsen,
W. Orejudos,
Y. B. Pan,
Y. Saadi,
I. J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
J. M. Yamartino,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Searches for supersymmetric particles in channels with one or more
photons and missing energy have been performed with data collected by
the ALEPH detector at LEP. The data consist of 11.1 pb-1 at
sqrt(s)=161 GeV, 1.1 pb-1 at 170 GeV and 9.5 pb-1
at 172 GeV. The
e+e--->νν¯γ(γ) cross
section is measured. The data are in good agreement with predictions
based on the Standard Model, and are used to set upper limits on the
cross sections for anomalous photon production. These limits are
compared to two different SUSY models and used to set limits on the
neutralino mass. A limit of 71 GeV/c2 at 95% C.L. is set on
the mass of the lightest neutralino
(τχ10<= 3 ns) for the
gauge-mediated supersymmetry breaking and LNZ models. © 1998
Physics Letters B 01/1998; 420:127-139. · 3.95 Impact Factor
-
ALEPH Collaboration,
R. Barate,
D. Buskulic,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
J.-Y. Nief, [......],
J. Nielsen,
W. Orejudos,
Y. B. Pan,
Y. Saadi,
I. J. Scott,
J. Walsh,
Sau Lan Wu,
X. Wu,
J. M. Yamartino,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Searches for scalar top and bottom quarks have been performed with data
collected by the ALEPH detector at LEP. The data sample consists of 21.7
pb-1 taken at sqrt(s) = 161, 170, and 172 GeV and 5.7
pb-1 taken at sqrt(s) = 130 and 136 GeV. No evidence for
scalar top quarks or scalar bottom quarks was found in the channels
t~-->cχ, t~-->blν~, and b~-->bχ. For the channel
t~-->cχ a limit of 67 GeV/c2has been set on the scalar
top quark mass, independent of the mixing angle between the
supersymmetric partners of the left and right-handed states of the top
quark. This limit assumes a mass difference between the t~ and the χ
of at least 10 GeV/c2. For the channel t~-->blν~ the
mixing-angle independent scalar top limit is 70 GeV/c2,
assuming a mass difference between the t~ and the ν~ of at least 10
GeV/c2. For the channel b~-->bχ, a limit of 73
GeV/c2has been set on the mass of the supersymmetric partner
of the left-handed state of the bottom quark. This limit is valid if the
mass difference between the b~ and the χ is at least 10
GeV/c2.
Physics Letters B 10/1997; 413:431-446. · 3.95 Impact Factor
-
R Barate,
Damir Buskulic,
D Décamp,
P Ghez,
C Goy,
J P Lees,
A Lucotte,
M N Minard,
J Y Nief,
B Pietrzyk, [......],
J Nielsen,
W Orejudos,
Y B Pan,
Y Saadi,
I J Scott,
J Walsh,
Wu Sau Lan,
X Wu,
J M Yamartino,
G Zobernig
[show abstract]
[hide abstract]
ABSTRACT: In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e+e- collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb-1 was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be sigma_WW = 4.23 +-0.73 (stat.) +- 0.19 (syst.) pb From this cross-section, the W mass is derived within the framework of the Standard Model: MW = 80.14 +- 0.34 (stat.) +- 0.09 (syst.) +- 0.03 (LEP~energy) GeV/c2.
Physics Letters B 02/1997; 401:347-362. · 3.95 Impact Factor
-
D. Buskulic,
I. de Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J.-P. Lees,
A. Lucotte,
M.-N. Minard,
J.-Y. Nief,
P. Odier, [......],
Y. B. Pan,
Y. Saadi,
I. J. Scott,
A. M. Walsh,
J. Walsh,
Lan Wu Sau,
X. Wu,
J. M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Two samples of exclusive semileptonic decays, 579 B0 ->
D*+l-νl events and 261 B0
-> D+l-νl events, are selected
from approximately 3.9 million hadronic Z decays collected by the ALEPH
detector at LEP. From the reconstructed differential decay rate of each
sample, the product of the hadronic form factor F(ω) at zero
recoil of the D(*)+ meson and the CKM matrix element
Vcb are measured to be FD*+ (1)
Vcb = (31.9 +/- 1.8stat +/- 1.9syst)
× 10-3,FD+ (1) Vcb =
(27.8 +/- 6.8stat +/- 6.5syst) ×
10-3. The ratio of the form factorsFD+
(1) and FD*+ (1) is measured to
beFD+ (1)/FD*+ (1) = 0.87
+/- 0.22stat +/- 0.21syst. A value of
Vcb is extracted from the two samples, using theoretical
constraints on the slope and curvature of the hadronic form factors and
their normalization at zero recoil, with the result Vcb =
(34.4 +/- 1.6stat +/- 2.3syst +/-
1.4th) × 10-3. The branching fractions are
measured from the two integrated spectra to be Br(B0 ->
D*+l-νl) = (5.53 +/-
0.26stat +/- 0.52syst) %, Br(B0 ->
D+l-νl) = (2.35 +/-
0.20stat +/- 0.44syst) %.
Physics Letters B 01/1997; 395:373-387. · 3.95 Impact Factor
-
ALEPH Collaboration,
D. Buskulic,
I. De Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J. P. Lees,
A. Lucotte,
M. N. Minard,
P. Odier, [......],
M. Schmitt,
I. J. Scott,
V. Sharma,
J. D. Turk,
A. M. Walsh,
Sau Lan Wu,
X. Wu,
J. M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and
backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the
period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing
the original quark and antiquark is measured for
b[`(b)]b\bar b
and
c[`(c)]c\bar c
events in subsamples selected by their long lifetimes or using fastD*’s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation
between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is
shown that differences between light quark charge separations and the measured average can be determined using hadronisation
models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons andΛ’s. The separations are used to measure the electroweak mixing angle precisely as sin2
ϑ
w
eff
=0.2322±0.0008(exp.stat.) ±0.0007(exp.syst.)±0.0008(sep.). The first two errors are due to purely experimental sources whereas
the third stems from uncertainties in the quark charge separations.
Zeitschrift für Physik C 06/1996; 71(3):357-378.
-
ALEPH Collaboration,
D. Buskulic,
I. De Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J. P. Lees,
A. Lucotte,
M. N. Minard,
P. Odier, [......],
Y. Saadi,
M. Schmitt,
I. J. Scott,
V. Sharma,
A. M. Walsh,
Sau Lan Wu,
X. Wu,
J. M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The lifetimes of theB
0 andB
+ mesons have been measured with theAleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991–1994. In the first of three
methods, semileptonic decays ofB
0 andB
+ mesons were partially reconstructed by identifying events containing a lepton with an associatedD*− or[`(D)]0\bar D^0 meson. The second method used fully reconstructedB
0 andB
+ mesons. The third method, used to measure theB
0 lifetime, employed a partial reconstruction technique to identifyB
0→D*−
π
+
X decays.
The combined results are
t0 = 1.55 ±0.06 ±0.03 ps, t+ = 1.58 ±0.09 ±0.03 ps, \tfract+ t0 = 1.03 ±0.08 ±0.02. \begin{gathered} \tau _0 = 1.55 \pm 0.06 \pm 0.03 ps, \hfill \\ \tau _ + = 1.58 \pm 0.09 \pm 0.03 ps, \hfill \\ \tfrac{{\tau _ + }}{{\tau _0 }} = 1.03 \pm 0.08 \pm 0.02. \hfill \\ \end{gathered}
.
Zeitschrift für Physik C 04/1996; 71(1):31-44.
-
D. Buskulic,
I. de Bonis,
D. Decamp,
P. Ghez,
C. Goy,
J. P. Lees,
A. Lucotte,
M. N. Minard,
P. Odier,
B. Pietrzyk, [......],
Y. Saadi,
M. Schmitt,
I. J. Scott,
V. Sharma,
A. M. Walsh,
Sau Lan Wu,
X. Wu,
J. M. Yamartino,
M. Zheng,
G. Zobernig
[show abstract]
[hide abstract]
ABSTRACT: The lifetimes of the B 0 and B + mesons have been
measured with the Aleph detector at LEP, using approximately 3 million
hadronic Z decays collected in the period 1991 1994. In the first of
three methods, semileptonic decays of B 0 and B +
mesons were partially reconstructed by identifying events containing a
lepton with an associated D*- orbar D^0 meson. The
second method used fully reconstructed B 0 and B +
mesons. The third method, used to measure the B 0 lifetime,
employed a partial reconstruction technique to identify B
0→ D*- π + X decays. The
combined results are begin{gathered} tau _0 = 1.55 ± 0.06
± 0.03 ps, \ tau _ + = 1.58 ± 0.09 ± 0.03 ps, \
tfrac{{tau _ + }}{{tau _0 }} = 1.03 ± 0.08 ± 0.02. \ .
Zeitschrift für Physik C 02/1996; 71:31-44.
-
Damir Buskulic,
I De Bonis,
D Décamp,
P Ghez,
C Goy,
J P Lees,
A Lucotte,
M N Minard,
P Odier,
B Pietrzyk, [......],
M Schmitt,
I J Scott,
V Sharma,
J Turk,
A M Walsh,
Wu Sau Lan,
X Wu,
J M Yamartino,
M Zheng,
G Zobernig
[show abstract]
[hide abstract]
ABSTRACT: Search for supersymmetric particles in e+e- collisions at centre-of-mass energies of 130 and 136 GeV. Searches for supersymmetric particles produced in e+e- collisions at centre-of-mass energies of 130 and 136 GeV have been performed in a data sample of 5.7 pb-1 collected in the autumn of 1995 by the ALEPH detector at LEP. No candidate events were found, allowing limits to be set on the masses and production cross-sections of scalar leptons, scalar tops charginos and neutralinos. The domains previously excluded at LEP1 are substantially extended. For instance, masses of gaugino-like charginos smaller than 67.8 GeV/c2 are excluded at the 95% C.L. for scalar neutrino masses larger than 200 GeV/c2.
Physics Letters B 02/1996; 373((1-3)):246 - 260. · 3.95 Impact Factor
