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1.
《The European Physical Journal C - Particles and Fields》2008,55(4):525-538
The effect of the heavy b-quark mass on the two, three and four-jet rates is studied using LEP data collected by the DELPHI
experiment at the Z peak in 1994 and 1995. The rates of b-quark jets and light quark jets (ℓ=uds) in events with n=2, 3, and
4 jets, together with the ratio of two and four-jet rates of b-quarks with respect to light-quarks, Rn
bℓ, have been measured with a double-tag technique using the CAMBRIDGE jet-clustering algorithm. A comparison between experimental
results and theory (matrix element or Monte Carlo event generators such as PYTHIA, HERWIG and ARIADNE) is done after the hadronisation
phase.
Using the four-jet observable R4
bℓ, a measurement of the b-quark mass using massive leading-order calculations gives: This result is compatible with previous three-jet determinations at the MZ energy scale and with low energy mass measurements evolved to the MZ scale using QCD renormalisation group equations. 相似文献
2.
A novel high precision method measures the b-quark forward-backward asymmetry at the Z pole on a sample of 3,560,890 hadronic events collected with the DELPHI detector in 1992 to 2000. An enhanced impact parameter tag provides a high purity b sample. For event hemispheres with a reconstructed secondary vertex the charge of the corresponding quark or anti-quark is determined using a neural network which combines in an optimal way the full available charge information from the vertex charge, the jet charge and from identified leptons and hadrons. The probability of correctly identifying b-quarks and anti-quarks is measured on the data themselves comparing the rates of double hemisphere tagged like-sign and unlike-sign events. The b-quark forward-backward asymmetry is determined from the differential asymmetry, taking small corrections due to hemisphere correlations and background contributions into account. The results for different centre-of-mass energies are:
.Combining these results yields the b-quark pole asymmetry
Received: 22 July 2004, Revised: 9 December 2004, Published online: 4 February 2005 相似文献
3.
Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with
the data recorded by the DELPHI detector at LEP. From measurements of the inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been
used to determine parameters which enter into the extraction of |Vcb| from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are:
and include corrections at order 1/mb3. Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of |Vcb| is obtained:
Received: 26 April 2005, Revised: 16 September 2005, Published online: 16 November 2005 相似文献
4.
《The European Physical Journal C - Particles and Fields》2006,47(2):309-335
The mass of the W boson is determined from the direct reconstruction of W decays in WW→qq̄qq̄ and WW→ℓνqq̄ events in e+e- collisions at LEP. The data sample corresponds to an integrated luminosity of 683 pb-1 collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection
a new procedure is adopted in which low energy particles are not considered in the mass determination from the qq̄qq̄ channel.
The combined result from all channels is
where FSI represents the possible effects of final state interactions in the qq̄qq̄ channel and LEP indicates the uncertainty
in the beam energy. From two-parameter fits to the W mass and width, the W width is found to be
相似文献
5.
《The European Physical Journal C - Particles and Fields》2008,55(1):1-38
A measurement of the W boson mass and width has been performed by the DELPHI collaboration using the data collected during
the full LEP2 programme (1996–2000). The data sample has an integrated luminosity of 660 pb-1 and was collected over a range of centre-of-mass energies from 161 to 209 GeV.
Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both
the W+W-→ℓν̄ℓqq̄’ and W+W-→qq̄’q̄q’ channels. The W mass result for the combined data set is where FSI represents the uncertainty due to final state interaction effects in the qq̄’q̄q’ channel, and LEP represents that
arising from the knowledge of the collision energy of the accelerator. The combined value for the W width is These results supersede all values previously published by the DELPHI collaboration.
This paper is dedicated to the memory of Carlo Caso. 相似文献
6.
Using the OPAL detector at LEP, the running of the effective QED coupling α(t) is measured for space-like momentum transfer from the angular distribution of small-angle Bhabha scattering. In an almost
ideal QED framework, with very favourable experimental conditions, we obtain:
where the first error is statistical, the second is the experimental systematic and the third is the theoretical uncertainty.
This agrees with current evaluations of α(t). The null hypothesis that α remains constant within the above interval of -t is excluded with a significance above 5σ. Similarly, our results are inconsistent at the level of 3σ with the hypothesis
that only leptonic loops contribute to the running. This is currently the most significant direct measurement where the running
α(t) is probed differentially within the measured t range.
Received: 2 March 2005, Revised: 30 August 2005, Published online: 3 November 2005 相似文献
7.
《The European Physical Journal C - Particles and Fields》2006,47(2):295-307
Data from e+e- annihilation into hadrons at centre-of-mass energies between 91 GeV and 209 GeV collected with the OPAL detector at LEP,
are used to study the four-jet rate as a function of the Durham algorithm resolution parameter ycut. The four-jet rate is compared to next-to-leading order calculations that include the resummation of large logarithms. The
strong coupling measured from the four-jet rate is
in agreement with the world average. Next-to-leading order fits to the D-parameter and thrust minor event-shape observables
are also performed for the first time. We find consistent results, but with significantly larger theoretical uncertainties. 相似文献
8.
R. Akers G. Alexander J. Allison N. Altekamp K. Ametewee K. J. Anderson S. Anderson S. Arcelli S. Asai D. Axen et al. 《Zeitschrift fur Physik C Particles and Fields》1995,67(3):365-378
The forward-backward asymmetry of
has been measured using approximately 2.15 million hadronicZ
0 decays collected at the LEP e+e– collider with the OPAL detector. A lifetime tag technique was used to select an enriched
event sample. The measurement of the
asymmetry was then performed using a jet charge algorithm to determine the direction of the primary quark. Values of:
相似文献
9.
The L Collaboration 《The European Physical Journal C - Particles and Fields》2006,45(3):569-587
The mass and the total decay width of the W boson are measured with the L3 detector at the LEP e+e– collider using W-boson pairs produced in 0.7 fb–1 of data collected at centre-of-mass energies between 161 and 209 GeV. Combining semi-leptonic and fully-hadronic final states,
the mass and the width of the W boson are determined to be
10.
The inverse scattering problem for the Zakharov-Shabat system
, is considered. It is solved by reduction to the inverse scattering problem for two coupled Zakharov-Shabat systems in a
4n-dimensional space:
.
This work has been done as part of the program ‘Recherche Coopérative sur Programme No. 264: Etude interdisciplinaire des
problèmes inverses’.
Physique Mathématique et Théorique, Equipe de recherche associée au CNRS, No. 154. 相似文献
11.
OPAL Collaboration G. Alexander J. Allison N. Altekamp K. Ametewee K. J. Anderson S. Anderson S. Arcelli S. Asai D. Axen et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):543-560
Symmetric three-jet events are selected from hadronic Z0 decays such that the two lower energy jets are each produced at an angle of about 150° with respect to the highest energy
jet. In some cases, a displaced secondary vertex is reconstructed in one of the two lower energy jets, which permits the other
lower energy jet to be identified as a gluon jet through anti-tagging. In other cases, the highest energy jet is tagged as
a b jet or as a light quark (uds) jet using secondary vertex or track impact parameter and momentum information. Comparing
the two lower energy jets of the events with a tag in the highest energy jet to the anti-tagged gluon jets yields a direct
comparison of b, uds and gluon jets, which are produced with the same energy of about 24 GeV and under the same conditions.
We observe b jets and gluon jets to have similar properties as measured by the angular distribution of particle energy around
the jet directions and by the fragmentation functions. In contrast, gluon jets are found to be significantly broader and to
have a markedly softer fragmentation function than uds jets. For thek
⊥ jet finder withy
cut=0.02, we find
as the ratios of the mean charged particle multiplicity in the gluon jets compared to the b and uds jets. Results are also
reported using the cone jet finder. 相似文献
12.
G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2006,45(2):307-335
The mass and width of the W boson are measured using e+e– → W+W– events from the data sample collected by the OPAL experiment at LEP at centre-of-mass energies between 170 GeV and 209 GeV.
The mass (mW) and width (ΓW) are determined using direct reconstruction of the kinematics of W+W– →
and W+W– →
events. When combined with previous OPAL measurements using W+W– →
events and the dependence on of the WW production cross-section at threshold, the results are determined to be
13.
A. Bartl W. Majerotto K. Mönig A. N. Skachkova N. B. Skachkov 《Physics of Particles and Nuclei Letters》2012,9(1):29-46
We study pair production of scalar top quarks (stop, \(\tilde t_1\)) in polarized photon-photon collisions with the subsequent decay of the top squarks into b quarks and charginos \(\tilde t_1 \to b\tilde \chi _1^ \pm\). We simulate this process by using PYTHIA6.4 for an electron beam energy \(2E_{beam}^e = \sqrt {s_{ee} } = 1000 GeV\). The energy spectrum of back-scattered photons is generated by CIRCE2 program. A set of criteria for physical variables is proposed which leads to a good separation of stop signal events from top quark pair production, being the main background. These criteria allow us to reconstruct the mass of the top squark, provided that the neutralino mass is known. 相似文献
14.
Riazuddin 《The European Physical Journal C - Particles and Fields》2007,51(3):697-699
It is proposed that light neutrinos form a triplet in a global SU(3) symmetry in the mass eigenstate basis. Assuming that
the SU(3) symmetry is broken in the direction , and after going to the flavor basis, we predict the atmospheric mixing angles sin2θ23=0.5 and sinθ13=0, if νμ–ντ symmetry is assumed. In the flavor basis, the diagonal part of the matrix coefficient of b (the dominant part) is found to
transform like . Imposing the same condition on the matrix coefficient of a fixes the solar mixing angle, . The implications for neutrinoless double beta decay are discussed. 相似文献
15.
The decay chain
is identified in a sample of 3.9 million hadronic Z decays collected with the OPAL detector at LEP. The branching ratio BR
is measured to be
for the J
P
=1+ (D0
1) state. For decays into the J
P
=2+ (D2
*0) state, an upper limit of 1.4 x 10-3 is placed on the branching ratio at the 95% confidence level.Received: 20 December 2002, Revised: 15 April 2003, Published online: 12 September 2003 相似文献
16.
Chao-Hsi Chang Jiao-Kai Chen Zhen-Yun Fang Bing-Quan Hu Xing-Gang Wu 《The European Physical Journal C - Particles and Fields》2007,50(4):969-978
The light top-squark may be the lightest squark, and its lifetime may be ‘long enough’ in a kind of SUSY models that have not been ruled out yet
experimentally, so colorless ‘supersymmetric hadrons (superhadrons)’ (q is a quark excluding the t-quark) may be formed as long as the light top-squark can be produced. The fragmentation function of into heavy ‘supersymmetric hadrons (superhadrons)’ (Q̄=c̄ or b̄) and hadronic production of the superhadrons are investigated quantitatively. The fragmentation function is
calculated precisely. Due to the difference in spin of the SUSY component, the asymptotic behavior of the fragmentation function
is different from those of the existing ones. The fragmentation function is also applied to compute the production of heavy
superhadrons at the hadronic colliders Tevatron and LHC in the so-called fragmentation approach. The resultant cross-section
for the heavy superhadrons is too small to observe at Tevatron, but large enough at LHC, when all the relevant parameters
in the SUSY models are taken within the favored region for the heavy superhadrons. The production of ‘light superhadrons’
(q=u,d,s) is also roughly estimated with the same SUSY parameters. It is pointed out that the production cross-sections of
the light superhadrons may be much greater than those of the heavy superhadrons, so that even at Tevatron the light superhadrons may be produced
in great quantities.
PACS 12.38.Bx; 13.87.Fh; 12.60.Jv; 14.80.Ly 相似文献
17.
The branching ratio of beauty hadrons to final states containing two charm hadrons, Br(b
, has been measured using an inclusive method in hadronic Z0 decays with the OPAL detector at LEP. The impact parameter significance of tracks opposite tagged b-jets is used to differentiate b
decays from other decays. The result is
where det. is the systematic uncertainty due to the modelling of the detector, and
is the systematic uncertainty due to the modelling of the underlying physics. Using this result, the average number of charm plus anti-charm quarks produced in a beauty quark decay, nc, is found to be 1.12 + 0.11-0.10.Received: 11 July 2003, Published online: 18 May 2004 相似文献
18.
C. V. V. S. N. K. Santaram P. Tiruvenganna Rao 《Zeitschrift für Physik A Hadrons and Nuclei》1962,168(5):553-559
The band spectrum of PO was excited in a high frequency discharge from a 1/2 kW oscillator working at a frequency of 30 to 40 Mc/sec. A new doublet system of bands degraded to red designated asC′?X 2 Π r occuring in the region λ 2200–λ 2900 was observed and analyzed. The following vibrational quantum formula was derived for the inner heads (R 1 andQ 2)
$$\begin{gathered} v = ^{43854 \cdot 5} + 825 \cdot 8(\upsilon ' + \tfrac{1}{2}) - 6 \cdot 44(\upsilon ' + \tfrac{1}{2})^2 \hfill \\ ^{43631 \cdot 4} - 1232 \cdot 6(\upsilon '' + \tfrac{1}{2}) - 6 \cdot 48(\upsilon '' + \tfrac{1}{2})^2 . \hfill \\ \end{gathered}$$ 相似文献
19.
First measurements of
mesons production properties and their spin alignment in
charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD
experiment is performed in different kinematic regions. For
and
mesons produced in
CC interactions and decaying into
we have found the following yields per event:
and
respectively, while for the
and
mesons produced in
interactions the corresponding yields per event are:
and
. The results obtained for the
parameter,
and
for
and
produced in
CC interactions, are compared to theoretical predictions tuned on LEP measurements in
annihilation at the
pole. For
mesons produced in
interactions the measured
parameter is
.
PACS 13.15.+g, 13.60.Le, 13.87.Fh, 13.88.+e, 14.40.Ev 相似文献
20.
《The European Physical Journal C - Particles and Fields》2007,52(4):1021-1023
In an earlier paper [1], the background for Ke3 was over estimated due to an erroneous calculation of the electron identification efficiency. The correct ratios of the partial
widths involving this channel are and . Assuming the PDG value [2] for the K2π branching ratio, the measured branching fraction of Br (Ke3) continues to exceed the current PDG value [2]. The extracted value of |Vus|f+(0) is in agreement with the CKM unitary prediction; thus, our conclusions in [1] do not change.
The online version of the original article can be found at 相似文献
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