447 research outputs found
First evidence for a charm radial excitation, D*-prime
No full textUsing D mesons exclusively reconstructed in the DELPHI detector at LEP, an excess of 66\pm14(\mbox{stat.}) events is observed in the D final state with a mass of 2637\pm2(\mbox{stat.})\pm6(\mbox{syst.})~MeV/ and a full width smaller than 15~MeV/ (95\% C.L.). This signal is compatible with the expected decay of a radially excited D () meson
Measurement of the B-d(0) oscillation frequency using kaons, leptons and jet charge
No full textA measurement of the mass difference, Delta m(d), be tween the two physical B-d(0) states has been obtained from the analysis of the impact parameter distribution of a lepton emitted at large transverse momentum (p(t)) relative to the jet axis and from the analysis of the flight distance distribution of secondary vertices tagged by either a high p(t) lepton or an identified kaon. In the opposite hemisphere of the event, the charge of the initial quark has been evaluated using a high p(t) lepton, a charged kaon or the mean jet charge, With 1.7 million hadronic Z(0) decays recorded by DELPHI between 1991 and 1993, Delta m(d) is found to be: Delta m(d) = 0.531 (+0.050)(-0.046) (stat.) +/- 0.078 (syst.) ps(-1)
Kaon interference in the hadronic decays of the Z
No full textLink to publication Citation for published version (APA): Abreu, P., Agasi, E. E., Boudinov, E., Hao, W., Holthuizen, D. J., Kluit, P. M., ... van Eldik, J. E. (1996). Kaon interference in the hadronic decays of the Z. Physics Letters B, 379, 330. https://doi.org/10.1016/0370-2693(96)00572-2 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. EB ELSEWJER PHYSICS LETTERS B Physics Letters B 379 (1996) [330][331][332][333][334][335][336][337][338][339][340] Kaon interference in the hadronic decays of the Z" Abstract The first measurement of like-sign charged kaon correlations in hadronic decays of the p is presented, based on data collected by the DELPHI detector. The charged kaons are identified by means of ring imaging Cherenkov detectors. A significant enhancement at small values of the four:momentum difference is observed in the ratio of like-sign to unlikesign KK pairs and in the ratio of like-sign pairs to a simulated reference sample. An update of the measurement of KiK:!, interference is also presented. An enhancement is found in the production of pairs of Ki of similar momenta, as compared with a simulated reference sample. The measured Bose-Einstein correlation parameters A and r are similar for charged and neutral kaon pairs. The value of the Bose-Einstein correlation strength A is consistent with unity. ' On leave of absence from IHEP Serpukhov
pi+-, K+-, p and anti-p production in Z0 ---> q anti-q, Z0 ---> b anti-b, Z0 ---> u anti-u, d anti-d, s anti-s
No full textThe DELPHI experiment at LEP uses Ring Imaging Cherenkov detectors for particle identification. The good understanding of the RICH detectors allows the identification of charged pions, kaons and p rotons, covering the full momentum range from \mbox{0.7\!<\!p\!<\! 45.6~\gevc}. The \pipm,~\kapm, p and \pbar normalised production rates, their differential cross sections, multiplicities a nd the maxima \xipst of the \mbox{\xip=\ln(1/\xp)} distributions are measured for three event samples \zqqbar, ~\zbbbar and \zudsbar, selected from \mbox{}~\zzero deca ys collected by \delphi in 1994. The results are compared to the predictions of the \jetset string fragmentation model and the \herwig cluster fragmentation model. The Modified Leading Logarithm Ap proximation with Local Parton-Hadron Duality is tested. The \xipst dependence on the primary quark flavour is investigated and quantified for the different particle distributions. The \pipm, \kapm, p and \pbar multiplicities are measured with precisions from \%~to~\%. For the \zqqbar and \zbbbar event samples, these improve on previous measurements. The \pipm, \k apm, p and \pbar multiplicities for \zudsbar are presented for the first time
J / psi production in the hadronic decays of the Z
No full textJ/ψ mesons have been reconstructed from their decay to μ+μ- and e+e-, using the data collected by the DELPHI experiment during 1991 and 1992 at the LEP collider. From about 1 million hadronic Z decays 153 ± 17 J/ψ were found, 5.4 ± 2.3 ψ′ were obtained in the channel J/ψ (→μ+μ-)π+π- and 6.4 ± 2.7 χc in the channel J/ψ ( → μ+μ-)γ. As the dominant source of Jψ mesons is from bquarks, the following branching ratios: Br(b → J/ψ X) = (1.12 ± 0.12 (stat) ± 0.10 (syst.))%, Br(b → ψ′ X) = (0.48 ± 0.22 (stat.± 0.10 (syst.))%, Br(b → χc1 X) = (1.4 ± 0.6 (stat.)-0.2+0.4 (syst.))% were measured. From the proper time distribution of the J/ψ sample, the average lifetime of b-hadrons decaying into J/ψ was found to be: τB = 1.50-0.21+0.24 (stat.) ± 0.03 (syst.) ps. A search for completely reconstructed B meson decays to final states including a J/ψ gave a signal of 15 ± 5 events.0info:eu-repo/semantics/publishe
Measurement of time dependent B(d)0 - anti-B(d)0 mixing
No full textThe time dependent mixing of Bd0-B̄d0 mesons has been observed by using the correlations between the charge of D* mesons and the weighted mean charge of particles in each hemisphere. From a reconstructed D*± sample corresponding to about 1.7 million hadronic Z0 decays, the mass difference between the two Bd0 mass eigenstates has been measured to be Δm = 0.50±0.12 (stat.) ± 0.06 (syst.) (Latin small letter h with stroke sign)/ps or, converting into eV/c2: Δm = [3.29±0.79 (stat.) ± 0.39 (syst.)] 10-4 eV/c2
Measurement of B(d)0 - anti-B(d)0 oscillations
No full textBd 0meson oscillations are measured in hadronic Z0decays using the charge of a lepton or the mean charge of an event hemisphere to sign the presence of a b or a b quark when it is produced, and using the charge of a lepton emitted at large ptor of a D∗±to sign the presence of a B or a B meson when it decays. With 3.2 million hadronic Z0decays registered by DELPHI between 1991 and 1994, the mass difference Δmdbetween the two physical Bd 0states is measured in four channels: Δmd= 0.523 ± 0.072 ± 0.043 ps-1(D∗±- Qhem) Δmd= 0.493 ± 0.042 ± 0.027 ps-1(ℓ - Qhem) Δmd= 0.499 ± 0.053 ± 0.015 ps-1((π∗- ℓ) - Qhem) Δmd= 0.480 ± 0.040 ± 0.051 ps-1(ℓ - ℓ). Taking into account the statistical overlap between these measurements and the common systematic uncertainties, the combined result is: Δmd= 0.497 ± 0.035 ps-1.0info:eu-repo/semantics/publishe
Determination of ǀVcb☐from the semileptonic decay B0 → D*-l+ν
No full textSemileptonic decays B→ D*-l+νX were selected from a sample of 3.1 million hadronic Z decays collected by the DELPHI detector at LEP. A topological search for semileptonic B decays to resonant and non-resonant D*-π+ states was performed and the ratio of the branching fractions: Br(B → D*-l+νX)/Br(B → D*-+νX) + Br(B0 → + D*-l+ν) = 0.19 ± 0.10(stat) ± 0.06(syst) was determined. Taking into account this contribution, the differential decay width of B0 → D*-l+ν was measured as a function of the momentum transfer from the B to the D*- in two separate analyses, using exclusive and inclusive methods of D*- reconstruction. The distributions were fitted over the full momentum transfer range to extract the product of {pipe}Vcb{pipe} times the normalization of the decay form factor F(q2max): F(q2max){pipe}Vcb{pipe} = (35.4 ± 1.9(stat) ± 2.4(syst)) · 10-3. The value of {pipe}Vcb{pipe} was computed using theoretical calculations of F(q2max), giving: {pipe}Vcb{pipe} = (38.9 ± 2.0(stat) ± 2.6(syst) ± 1.7(theory)) · 10-3. The total branching fraction Br(B0 → D*-l+ν) was determined to be: Br(130, D*-l+v) = (5.52 ± 0.17(stat) ± 0.68(syst))%. © Springer-Verlag 1996
A Measurement of B meson production and lifetime using D lepton- events in Z0 decays
No full textA study of B meson decays into DlX final states is presented. In these events, neutral and charged D mesons originate predominantly from B+ and B0 decays, respectively. The dilution of this correlation due to D** production has been taken into account. From 263 700 hadronic Z0 decays collected in 1991 with the DELPHI detector at the LEP collider, 92 D0→K-π+, 35 D+→K-π+π+ and 61 D*0→D0π+ followed by D0→K-π+ or D0→K-π+π+π -, are found with an associated lepton of the same charge as the kaon. From the D0l- and D*+l-, the probability fd that a b quark hadronizes into a B- (or {Mathematical expression}) meson is found to be 0.44 ±0.08±0.09, corresponding to a total (Bs+Λb) hadronization fraction of 0.12-0.12 +0.24. By reconstructing the energy of each B meson, the b quark fragmentation is directly measured for the first time. The mean value of the B meson energy fraction is: {Mathematical expression} Reconstructing D-lepton vertices, the following B lifetimes are measured: {Mathematical expression} and an average τ(B)=1.23-0.13 +0.14(stat.)±0.15(syst.) ps is found. Allowing for decays into {Mathematical expression}, the B+ and B0 lifetimes are: {Mathematical expression} © 1993 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Determination of |V| from the semileptonic decay B --> Dl
No full textSemileptonic decays B \rightarrow D^{*-} \ell^+ \nu X were selected from a sample of 3.1 million hadronic Z decays collected by the DELPHI detector at LEP. A topological search for semileptonic B decays to resonant %(D^{**}) and non-resonant D^{*-} \pi^{+} states was performed and the ratio of the branching fractions: \frac {Br ({\mathrm{B} \rightarrow {\mathrm D}^{*-}} \ell^+ \nu X)} {Br({\mathrm{B} \rightarrow {\mathrm D}^{*-}} \ell^+ \nu X) + Br( {\mathrm{B}^0 \rightarrow \mathrm{D}^{*-}} \ell^+ \nu)} = 0.19 \pm 0.10({\mathrm{stat}}) \pm 0.06({\mathrm{syst}}) was determined. Taking into account this contribution, %DB the differential production fraction of the decay the differential decay width of {\mathrm{B}^{0} \rightarrow \mathrm{D}^{*-}} \ell^+ \nu was measured as a function of the momentum transfer from the B to the D^{*-} in two separate analyses, using exclusive and inclusive methods of D^{*-} reconstruction. The distributions were fitted %DB with a linear function over the full momentum transfer range to extract the product of \mathrm{|V_{cb}|} times the normalization of the decay form factor F(q^2_{max}): F(q^2_{max})\mathrm{|V_{cb}|} = (35.0 \pm 1.9({\mathrm{stat}}) \pm 2.3({\mathrm{syst}}) )~\cdot~10^{-3}. The value of \mathrm|V_{cb}| was computed using theoretical calculations of F(q^2_{max}), giving: {\mathrm{|V_{cb}|}} = (38.5 \pm 2.1({\mathrm{stat}}) \pm 2.5({\mathrm{syst}}) \pm 1.7({\mathrm{theory}}))~\cdot~10^{-3}. The total branching fraction Br(\mathrm{B}^{0} \rightarrow D^{*-} \ell^+ \nu) was determined to be: Br ({\mathrm{B}^0 \rightarrow \mathrm{D}^{*-}} \ell^+ \nu) = (5.47 \pm 0.16({\mathrm{stat}}) \pm 0.67({\mathrm{syst}})) \%
- …
