K. Doroba

DELPHI data collected at centre-of-mass energies up to 208 GeV have been analysed to search for charginos, neutralinos and sfermions in the framework of the Minimal Supersymmetric Standard Model (MSSM) with R-parity conservation. No evidence for a signal was found in any of the channels. The results of each search were used to derive limits on production cross-sections and particle masses. In addition, the combined result of all searches excludes regions in the parameter space of the constrained MSSM, leading to limits on the mass of the Lightest Supersymmetric Particle and other supersymmetric particles.

The production of single- and multi-photon events has been studied in the reaction e+e- -> gamma (gamma) + invisible particles. The data collected with the DELPHI detector during the years 1999 and 2000 at centre-of-mass energies between 191 GeV and 209 GeV was combined with earlier data to search for phenomena beyond the Standard Model. The measured number of light neutrino families was consistent with three and the absence of an excess of events beyond that predicted by the Standard Model processes was used to set limits on new physics. Both model-independent searches and searches for new processes predicted by supersymmetric and extra-dimensional models have been made. Limits on new non-standard model interactions between neutrinos and electrons were also determined.

The multiplicities of charged secondaries in proton-proton collisions were determined using the split-field-magnet detector at the CERN Intersecting Storage Rings (ISR). Measurements are presented on multiplicity distributions both for inelastic and non-single-diffractive events at four different energies √s=30.4, 44.5, 52.6, and 62.2 GeV. The results reported here represent the first high-statistics measurement of charged multiplicity distributions at ISR energies with a magnetic detector covering nearly the full solid angle.Received 23 March 1984DOI:https://doi.org/10.1103/PhysRevD.30.528©1984 American Physical Society

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We have measured the differential cross section for ¯pp and pp elastic scattering at √s=53 GeV in the interval 0.5<|t|<4.0 (GeV/c)2 at the CERN intersecting storage rings using the split-field magnet detector. The shape of the differential cross section differs significantly between ¯pp and pp scattering in the region 1.1<|t|<1.5 (GeV/c)2, with ¯pp data showing a less pronounced dip structure than pp data.Received 1 February 1985DOI:https://doi.org/10.1103/PhysRevLett.54.2180©1985 American Physical Society

We have measured the differential cross section for pp and p̄p elastic scattering at √s = 31, 53 and 62 GeV in the interval 0.05 < |t| < 0.85 GeV2 at the CERN ISR using the Split Field Magnet detector. At 53 and 62 GeV, for 0.17 < |t| < 0.85 GeV2 both pp and p̄p data show simple exponential behaviour in t; at √s = 31 GeV the data for 0.05 < |t| < 0.85 GeV2 are consistent with a change in slope near |t| = 0.15 GeV2.

A search for pair-produced doubly charged Higgs bosons has been performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies between 189 and 209 GeV. No excess is observed in the data with respect to the Standard Model background. A lower limit for the mass of 97.3 GeV/c2 at the 95% confidence level has been set for doubly charged Higgs bosons in left–right symmetric models for any value of the Yukawa coupling between the Higgs bosons and the τ leptons.

We observe an increase of the average transverse momentum with the multiplicity of the charged particles produced in the central rapidity region of proton-proton collisions at ISR energies. The increase is smaller than that observed at the CERN proton-antiproton collider. The magnitude of the effect is the same for negative and positive particles.

The DELPHI detector at LEP has been used to measure multi-muon bundles originating from cosmic ray interactions with air. The cosmic events were recorded in “parasitic mode” between individual e+e− interactions and the total live time of this data taking is equivalent to 1.6 × 106 s. The DELPHI apparatus is located about 100 m underground and the 84 metres rock overburden imposes a cutoff of about 52 GeV/c on muon momenta. The data from the large volume Hadron Calorimeter allowed the muon multiplicity of 54,201 events to be reconstructed. The resulting muon multiplicity distribution is compared with the prediction of the Monte Carlo simulation based on CORSIKA/QGSJET01. The model fails to describe the abundance of high multiplicity events. The impact of QGSJET internal parameters on the results is also studied.

Single photons detected by the DELPHI experiment at LEP2 in the years 1997–2000 are reanalysed to investigate the existence of a single extra dimension in a modified ADD scenario with slightly warped large extra dimensions. The data collected at centre-of-mass energies between 180 and 209 GeV for an integrated luminosity of ∼650 pb−1 agree with the predictions of the Standard Model and allow a limit to be set on graviton emission in one large extra dimension. The limit obtained on the fundamental mass scale M D is 1.69 TeV/c 2 at 95% CL, with an expected limit of 1.71 TeV/c 2.

The inclusive cross sections for the production of high transverse momentum π+ and π− mesons in proton-proton interactions have been measured at the highest ISR energy √s = 63 GeV and at a c.m. production angle of 50°. The cross sections for π+ and π− mesons are compared as a function of transverse momentum. It is shown that the inclusive cross section of π− mesons decreases faster than the π+ cross section. particle σ(π±)/σ (charged particles) are presented as a function of transverse momentum.

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 $M_W = 80.336 \pm0.055 ({\text{Stat.}}) \pm0.028 ({\text{Syst.}}) \pm0.025 ({\text{FSI}}) \pm0.009 ({\text{LEP}}) \text{GeV}/c^2, $ 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 ${\Gamma_{W}} = 2.404 \pm0.140 ({\text{Stat.}}) \pm0.077 ({\text{Syst.}}) \pm0.065 ({\text{FSI}}) \text{GeV}/c^2. $ These results supersede all values previously published by the DELPHI collaboration.

The nature of b-quark jet hadronisation has been investigated using data taken at the Z peak by the DELPHI detector at LEP. Two complementary methods are used to reconstruct the energy of weakly decaying b-hadrons, $E_{\mathrm{B}}^{\mathrm{weak}}$ . The average value of $x^{\mathrm{weak}}_{\mathrm{B}} = E_{\mathrm{B}}^{\mathrm{weak}}/E_{\mathrm{beam}}$ is measured to be 0.699±0.011. The resulting $x^{\mathrm{weak}}_{\mathrm{B}}$ distribution is then analysed in the framework of two choices for the perturbative contribution (parton shower and Next to Leading Log QCD calculation) in order to extract measurements of the non-perturbative contribution to be used in studies of b-hadron production in other experimental environments than LEP. In the parton shower framework, data favour the Lund model ansatz and corresponding values of its parameters have been determined within PYTHIA 6.156 from DELPHI data: $$a= 1.84^{+0.23}_{-0.21}\quad\mbox{and}\quad b=0.642^{+0.073}_{-0.063}~\mathrm{GeV}^{-2},$$ with a correlation factor ρ=92.2%. Combining the data on the b-quark fragmentation distributions with those obtained at the Z peak by ALEPH, OPAL and SLD, the average value of $x^{\mathrm{weak}}_{\mathrm{B}}$ is found to be 0.7092±0.0025 and the non-perturbative fragmentation component is extracted. Using the combined distribution, a better determination of the Lund parameters is also obtained: $$a= 1.48^{+0.11}_{-0.10}\quad\mbox{and}\quad b=0.509^{+0.024}_{-0.023}~\mathrm{GeV}^{-2},$$ with a correlation factor ρ=92.6%.

Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qq̄ disintegrations of the Z0 were studied in the kinematic range 0.2<Eγ<1 GeV and transverse momentum with respect to the closest jet direction pT<80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17±0.06±0.27)×10-3 γ/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340±0.001±0.038)×10-3 γ/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4±0.2±0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.

A determination of the single W spin density matrix (SDM) elements in the reaction e+e-→W+W-→lνqq̄(l=e/μ) is reported at centre-of-mass energies between 189 and 209 GeV. The data sample used corresponds to an integrated luminosity of 520 pb-1 taken by DELPHI between 1998 and 2000. The single W SDM elements, ρττ' W± (τ,τ'=± 1 or 0), are determined as a function of the W- production angle with respect to the e- beam direction and are obtained from measurements of the W decay products by the application of suitable projection operators, Λττ', which assume the V-A coupling of the W-boson to fermions. The measured SDM elements are used to obtain the fraction of longitudinally polarised Ws, with the result: $\frac{\sigma_{\text{L}}}{\sigma_{{\text{tot}}}} = 24.9 \pm4.5({\text{stat}}) \pm2.2({\text{syst}})\%$ at a mean energy of 198 GeV. The SDM elements are also used to determine the triple gauge couplings Δg1 Z,Δκγ,λγ and g4 Z, $\tilde{\kappa}_{Z}$ and $\tilde{\lambda}_{Z}$ . For the CP-violating couplings the results of single parameter fits are: $g_4^{{Z}} = -0.39^{+0.19}_{-0.20}$ $\tilde{\kappa}_{{Z}} = -0.09^{+0.08}_{-0.05}$ $\tilde{\lambda}_{{Z}} = -0.08\pm0.07 .$ The errors are a combination of statistical and systematic errors. All results are consistent with the Standard Model.

The ${\ensuremath{\Sigma}}^{+}$ magnetic moment is measured to be $(2.38\ifmmode\pm\else\textpm\fi{}0.02){\ensuremath{\mu}}_{N}$ with use of 44 457 polarized ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{0}$ decays in a charged hyperon beam. The inclusively produced ${\ensuremath{\Sigma}}^{+}$ in this 210-GeV/c beam have a polarization of about 0.20 for production angles between 2.5 and 7.0 mrad.

An analysis of the direct soft photon production rate as a function of the parent jet characteristics is presented, based on hadronic events collected by the DELPHI experiment at LEP1. The dependences of the photon rates on the jet kinematic characteristics (momentum, mass, etc.) and on the jet charged, neutral and total hadron multiplicities are reported. Up to a scale factor of about four, which characterizes the overall value of the soft photon excess, a similarity of the observed soft photon behaviour to that of the inner hadronic bremsstrahlung predictions is found for the momentum, mass, and jet charged multiplicity dependences. However for the dependence of the soft photon rate on the jet neutral and total hadron multiplicities a prominent difference is found for the observed soft photon signal as compared to the expected bremsstrahlung from final state hadrons. The observed linear increase of the soft photon production rate with the jet total hadron multiplicity and its strong dependence on the jet neutral multiplicity suggest that the rate is proportional to the number of quark pairs produced in the fragmentation process, with the neutral pairs being more effectively radiating than the charged ones.

A search for single top production (e+e−→tc̄) via flavour changing neutral currents (FCNC) was performed using the data taken by the DELPHI detector at LEP2. The data analyzed have been accumulated at center-of-mass energies ranging from 189 to 208 GeV. Limits at 95% confidence level were obtained on the anomalous coupling parameters κγ and κZ.

The average transverse momentum and the size of the particle emitting source (measured via Bose-Einstein correlations) have been studied as functions of the charged particle density in the central region inp-p interactions at $$\sqrt s $$ =62, 44 and 31 GeV. Both the average transverse momentum and the source size increase with increasing density at all three energies. This effect, very weak at $$\sqrt s $$ =31 GeV, becomes stronger with increasing energy.

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -&gt; ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -&gt; ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.

The relative yield of high transverse momentum protons measured inpp interctions at the CERN ISR is calculated in the framework of simple parton models. Whereas models based exclusively on quark and gluon scattering fail to describe the data, the hypothesis of diquark scattering provides a quantitative understanding of the measured dependences on transverse momentum, polar angle, and centre-of-mass energy. Different assumptions on diquark structure functions are tested.

The ratios of high pT charged kaon to pion production cross sections at √s = 45 and 62 GeV are presented. The values of the K±π± ratios are essentially independent of both √s and xT = 2pT√s and are compatible with a strangeness suppression factor λ = 0.55. By contrast, the K−π− values fall with xT suggesting a gluonic origin of K−. QCD calculations agrees with the measurements.

The sources of negative pions are analysed in π+p interactions at 16 GeV/c. It is shown that the kinematics of resonance decay is crucial in determining the pions′ longitudinal and transverse momentum spectra. The identifiable meson resonances, of which η, ω, ϱ0 and f are the dominant ones, account for about 50% of all π−'s produced. The “direct” pions, i.e. those that are primary products of the π+p interactions, appear to constitute 10 to 30% of the total π− yield.

Recent data on the production ofη, ϱ0, ω and other mesons in hadron-hadron collisions at intermediate energies are studied. Their transverse spectra dσ/dpT2 are all found to be approximately exponential, with similar slopes, ∼3.4 (GeV/c)−2, up to about pT2 = 2(GeV/c)2. The inclusive yields of the mesons are broadly in agreement with quark model predictions. In the case of pions, a distimction is made between those directly produced and those produced indirectly via resonance decay. It is estimated that between 10% and 30% of pions are directly produced.

Multiplicity distributions of charged secondaries, σN(π−d) are obtained. The effective multiplicities σN(π−n) and σN(π−p) are extracted using the measured spectator momentum. The probability of double scattering PN is found to be independent of multiplicity.

Inclusive J/psi production in photon-photon collisions has been observed at LEP II beam energies. A clear signal from the reaction gamma gamma -&gt; J/psi+X is seen. The number of observed N(J/psi -&gt; mu+mu-) events is 36 +/- 7 for an integrated luminosity of 617 pb^{-1}, yielding a cross-section of sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the event shapes of different types of gamma gamma processes in the PYTHIA program, we conclude that (74 +/- 22)% of the observed J/psi events are due to `resolved' photons, the dominant contribution of which is most probably due to the gluon content of the photon.

Data are presented on Pomeron-Pomeron interactions which produce a centralπ + π − system in proton-proton collisions at $$\sqrt s = 62 GeV$$ at the CERN Intersecting Storage Rings. This process may favor the production of gluonic bound states. A partial-wave analysis of theπ + π − system shows evidence for the production of the statesf 0(975),f 0(1400), andf 2(1270). The fitted mass for thef 2(1270) is about 50 MeV below the world average. In addition, the production mechanism for thef 2(1270) is uniquely different from that for the other final states in that there is a correlation between the outgoing protons. this is consistent with a picture of two-gluon exchange with thef 2(1270) produced by gluon fusion, and could indicate that thef 2(1270) has a glueball component.

Abstract Measurements are presented of inclusive distributions in pp and p p interactions at √s = 53 GeV. The data were obtained at the CERN ISR using the Split Field Magnet spectrometer with a minimum bias trigger. The inclusive distributions are analyzed as functions of the transverse momentum, the rapidity and the Feynman-x variable.

The inclusive cross section for the production ofK 0 mesons, Λ and $$\bar \Lambda$$ particles in proton-proton interactions at $$\sqrt s = 63$$ GeV is presented. The produced particles have been detected in the full phase space. Behaviour of the longitudinal and transversal depandences of the cross sections are discussed. The total production cross sections for 0 mesons and Λ particles was determined to $$\sigma _{{\rm K}_S^0 } = (25.5 \pm 1.4)$$ mb andσ Λ =(7.8±1.2) mb respectively. A strong energy dependence of the production cross sections is observed.

We present a systematic study of the different mechanisms leading to $WW$ pair production at the Large Hadron Collider (LHC), both in the same-sign and opposite-sign channels, and we emphasize that the former offers much better potential for investigating non-resonant ${W}_{L}{W}_{L}$ scattering. We propose a new kinematic variable to isolate the ${W}_{L}{W}_{L}$ scattering component in same-sign $WW$ production at the LHC. Focusing on purely leptonic $W$ decay channels, we show that it considerably improves the LHC capabilities to shed light on the electroweak symmetry breaking mechanism after collecting $100\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data at $\sqrt{s}=14\text{ }\text{ }\mathrm{TeV}$. The new variable is less effective in the opposite-sign $WW$ channel due to different background composition.

The form factor of Λb0 baryons is estimated using 3.46×106 hadronic Z decays collected by the DELPHI experiment between 1992 and 1995. Charmed Λc+ baryons fully reconstructed in the pK−π+, pK0S, and Λπ+π+π− modes, are associated to a lepton with opposite charge in order to select Λb0→Λc+l−ν̄l decays. From a combined likelihood and event rate fit to the distribution of the Isgur–Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be ρ̂2=2.03±0.46(stat)+0.72−1.00(syst). The exclusive semileptonic branching fraction Br(Λb0→Λc+l−ν̄l) can be derived from ρ̂2 and is found to be (5.0+1.1−0.8(stat)+1.6−1.2(syst))%. Limits on other branching fractions are also obtained.

We have measured the production polarization of 265- and 310-GeV/c ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ in the inclusive reaction $p+\mathrm{Cu}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{\ensuremath{-}}+X$ using 400-GeV/c protons. The polarization was analyzed via the asymmetry in the weak decay ${\ensuremath{\Sigma}}^{\ensuremath{-}}\ensuremath{\rightarrow}n+{\ensuremath{\pi}}^{\ensuremath{-}}$, and has typical values of +0.20 with respect to the direction of the cross product of the incident-proton and ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ momenta. Using the spin-precession technique, we have determined the ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ magnetic moment to be -1.23\ifmmode\pm\else\textpm\fi{}0.03\ifmmode\pm\else\textpm\fi{}0.03 nuclear magnetons, where the statistical and systematic errors are shown separately.

These final results on e+e- -&gt; W+W- production cross-section measurements at LEP2 use data collected by the DELPHI detector at centre-of-mass energies up to 209 GeV. Measurements of total cross-sections, W angular differential distributions and decay branching fractions, and the value of the CKM element |V_{cs}| are compared to the expectations of the Standard Model. These results supersede all values previously published by DELPHI.

Data are presented for the exclusive reaction pp → pp π+ π− at $$\sqrt s = 62GeV$$ with two leading protons at large Feynman-x and a centrally produced π+;π− system. In this kinematical configuration one expects a substantial contribution from Double Pomeron Exchange, which is a potential source of glueballs. The experiment was performed at the CERN ISR using the Split Field Magnet spectrometer. In the mass range between 1,000 and 1,700 MeV/c2 the invariant mass distribution for the central π+;π− system exhibits a very significant signal for thef 0(1270) and no other obvious resonant states.

Neutral triple-gauge-boson couplings ZZZ, ZZγ and Zγγ have been studied with the DELPHI detector using data at energies between 183 and 208 GeV. Limits are derived on these couplings from an analysis of the reactions e+e-→Zγ, using data from the final states γff̄, with f=q or ν, from e+e-→ZZ, using data from the four-fermion final states qq̄qq̄, qq̄μ+μ-, qq̄e+e-, qq̄νν̄, μ+μ-νν̄ and e+e-νν̄, and from e+e-→Zγ*, in which the final state γ is off mass-shell, using data from the four-fermion final states qq̄e+e- and qq̄μ+μ-. No evidence for the presence of such couplings is observed, in agreement with the predictions of the Standard Model.

The data taken by DELPHI at centre-of-mass energies between 189 and 209 GeV are used to place limits on the CP-conserving trilinear gauge boson couplings Delta_g1z, lambda_gamma and Delta_kappag associated to W+W- and single W production at LEP2. Using data from the jjlv, jjjj, jjX and lX final states, where j, l and X represent a jet, a lepton and missing four-momentum, respectively, the following limits are set on the couplings when one parameter is allowed to vary and the others are set to their Standard Model values of zero: Delta_g1z = -0.025^{+0.033}_{-0.030}, lambda_gamma = 0.002^{+0.035}_{-0.035} and Delta_kappag = 0.024^{+0.077}_{-0.081} . Results are also presented when two or three parameters are allowed to vary. All observations are consistent with the predictions of the Standard Model and supersede the previous results on these gauge coupling parameters published by DELPHI.

We analyse the variation of the average transverse momentum, 〈pT〉, with the multiplicity of charged particles produced in pp, p̄p, dd and αα collisions at ISR energies. An increase of 〈pT〉 with increasing particle density p=ΔnΔy for charged particles produced in the central region is observed. The energy dependence of this effect and its dependence on the type of colliding particles are discussed.

The multiplicity distributions of charged secondaries in proton-proton interactions at $$\sqrt s = 31$$ , 44 and 62 GeV have been measured with high statistics using the split field magnet (SFM) detector at the CERN ISR. The multiplicity distributions for narrow bins in rapidity depend on the rapidity variable. The validity of KNO scaling is discussed. The negative binomial function fits well the charged and negative multiplicity data for full phase space and for central rapidity windows. The energy and the rapidity dependence of the negative binomial parameters, $$\bar n$$ andk, are presented. We also analyse their implications for a cascade model in terms of the average number of «clans» and of the average number of particles per «clan».

Bose-Einstein correlations between two equal charge pions were measured in pp and pp collisions at s = 63 GeV. The data were recorded at the CERN-ISR with the split field magnet detector (SFM) using minimum bias triggers. The second-order interference is used to determine the size and the degree of coherence of the pion source in pp and [ovbar|p]p collisions. They are found to be equal within errors.

We present evidence for fluctuations of the average transverse momentum in pp, pα and αα collisions at ISR energies. In thermodynamical models, this is interpreted as fluctuations in the temperature of hadronic interactions. We find that the effect does not depend on the energy of the collision, however, the fluctuations are smaller for αp and αα reactions than for pp interactions.

The composition of high pT particles is determined for pp collisions at a CMS energy s = 62 GeV at three CMS polar angles θ ≈ 10°, 20°, and 45°. The fractions of protons and antiprotons are given as functions of transverse momentum pT. The fractional yield of high pT protons depends strongly on θ, whereas the one for anti-protons is constant.

Data are presented for the first time on inclusive Pomeron-Pomeron interactions which produce a central systemX (composed mainly of multimeson states) in proton-proton collisions at $$\sqrt s $$ at the CERN ISR. The systemX has a Feynman-x distribution which is sharply peaked atx f=0, is inconsistent with any significant contributions from Reggeon exchange processes, and has an invariant mass dependence in good agreement with the predicted formM −2 . Kaon production is about 15% of pion production, nearly independent ofM x, while proton-antiproton production averages about 5% of pion production and increases withM x. The structure of the central systemX develops into a jetlike shape, asM x increases, as would be expected from a model of Pomeron fragmentation. The shape of thex f(π) distribution in the center of mass of theX system (although not proving existence) is consistent with asoft partonic substructure of the Pomeron.

Measurements of on-shell ZZ production are described, using data from the DELPHI experiment at LEP in e+e- collisions at centre-of-mass energies between 183 and 209 GeV, corresponding to an integrated luminosity of about 665 pb^{-1}. Results obtained in each of the final states q anti-q q anti-q, nu anti-nu q anti-q, mu+ mu- q anti-q, e+ e- q anti-q, tau+ tau- q anti-q, l+ l- l+ l-, and nu anti-nu l+ l- (with l=e,mu) are presented. The measured production cross-sections are consistent with the Standard Model expectations. These results update and supersede those already published at 183 and 189 GeV.

In the reaction e+e-→WW→(q1q̄2)(q3q̄4) the usual hadronization models treat the colour singlets q1q̄2 and q3q̄4 coming from two W bosons independently. However, since the final state partons may coexist in space and time, cross-talk between the two evolving hadronic systems may be possible during fragmentation through soft gluon exchange. This effect is known as colour reconnection. In this article the results of the investigation of colour reconnection effects in fully hadronic decays of W pairs in DELPHI at LEP are presented. Two complementary analyses were performed, studying the particle flow between jets and W mass estimators, with negligible correlation between them, and the results were combined and compared to models. In the framework of the SK-I model, the value for its κ parameter most compatible with the data was found to be: κSK-I=2.2+2.5 -1.3 corresponding to the probability of reconnection $\mathcal{P}_{\text{reco}}$ to be in the range $0.31 <\mathcal{P}_{{\text{reco}}} < 0.68$ at 68% confidence level with its best value at 0.52.

Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2<E γ ≤1 GeV and transverse momentum with respect to the parent muon p T <40 MeV/c, and 1<E γ ≤10 GeV and p T <80 MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z 0 decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06±0.12±0.07 in the photon energy range 0.2<E γ ≤1 GeV and 1.04±0.09±0.12 in the photon energy range 1<E γ ≤10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP.

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: $m_b(M_Z) = 3.76 \pm0.32 ({\text{stat}}) \pm0.17 ({\text{syst}}) \pm0.22 ({\text{had}}) \pm0.90 ({\text{theo}})\,\text{GeV}/c^2\,.$ 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.

The rapidity distribution of fast fragments of scattered partons has been measured in events triggered on a π+ of large transverse momentum, pT > 4 GeV/c. The energy was √s = 63 GeV. The data are compared to model calculations assuming spin-0 or spin-1 for the quantum exchanged in the underlying parton-parton scattering process. While the exchange of a spin-0 gluon is excluded by the data, a spin-1 gluon is found in agreement with the observations.

Measurements are presented of two-particle rapidity correlations in pp and pp at √s = 53 GeV. The data were recorded at the CERN-ISR using the Split Field Magnet spectrometer with a minimum bias trigger. Short range correlations in normal inelastic events with measured charged multiplicities nch ⩾ 4 are observed of pairs for charged particles in all charge combinations. Within the experimental errors no differences are observed between the analogous correlations in pp and pp interactions.

The production fractions of charged and neutral b-hadrons in b-quark events from Z0 decays have been measured with the DELPHI detector at LEP. An algorithm has been developed, based on a neural network, to estimate the charge of the weakly-decaying b-hadron by distinguishing its decay products from particles produced at the primary vertex. From the data taken in the years 1994 and 1995, the fraction of b̄-quarks fragmenting into positively charged weakly-decaying b-hadrons has been measured to be: f+=42.09±0.82(stat)±0.89(syst)%. Subtracting the rates for charged Ξ̄b+ and Ω̄b+ baryons gives the production fraction of B+ mesons: fBu=40.99±0.82(stat)±1.11(syst)%.

The PAC (pattern comparator) is a dedicated muon trigger for the CMS (Compact Muon Solenoid) experiment at the LHC (Large Hadron Collider). The PAC trigger processes signals provided by RPC (resistive plate chambers), a part of the CMS muon system. The goal of the PAC RPC trigger is to identify muons, measure their transverse momenta and select the best muon candidates for each proton bunch collision occurring every 25 ns. To perform this task it is necessary to deliver the information concerning each bunch crossing from many RPC chambers to the trigger logic at the same moment. Since the CMS detector is large (the muon hits are spread over 40 ns), and the data are transmitted through thousands of channels, special techniques are needed to assure proper synchronization of the data. In this paper methods developed for the RPC signal synchronization and synchronous transmission are presented. The methods were tested during the MTCC (magnet test and cosmic challenge). The performance of the synchronization methods is illustrated by the results of the tests.

Measurements are presented of R b, the ratio of the ${\mathrm{b}}\bar{\mathrm{b}}$ cross-section to the ${\mathrm{q}}\bar{\mathrm{q}}$ cross-section in e+e− collisions, and the forward-backward asymmetry A FB b at twelve energy points in the range $\sqrt{s}=130$ –207 GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions.

The tau lepton lifetime has been measured with the e(+) e(-) --> tau(+) tau(-) events collected by the DELPHI detector at LEP in the years 1991 - 1995. Three different methods have been exploited, using both one-prong and three-prong tau decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave tau(tau) ( 1 prong) = 291.8 +/- 2.3(stat) +/- 1.5(sys) fs. A third measurement using taus which decayed to three charged particles yielded tau(tau) (3 prong) = 288.6 +/- 2.4(stat) +/- 1.3(sys) fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be tau(tau) = 290.9 +/- 1.4(stat) +/- 1.0(sys) fs.

During the summer 2006, a first integrated test of a part of the CMS experiment was performed at CERN collecting a data sample of several millions of cosmic rays events. A fraction of the Resistive Plate Chambers system was successfully operated. Results on the RPC performance are reported.

The paper presents the concept of the Overlap Muon Track Finder (OTF) trigger for the CMS experiment in CERN as a system implemented in the modern FPGA device. The parametrized description of the complex data processing system, allowing further optimization by iterative simulations and recompilations, is presented. Problems associated with synthesis of such complex systems with currently available synthesis tools, and their workarounds are described.

The Overlap Muon Track Finder (OMTF) is the new system developed during the upgrade of the CMS experiment which includes the upgrade of its Level-1 trigger. It uses the novelty approach to finding muon candidates based on data received from three types of detectors: RPC, DT, and CSC . The upgrade of the trigger system requires also upgrade of the associated Data Acquisition (DAQ) system. The OMTF DAQ transmits the data from the connected detectors that were the basis for the Level-1 trigger decision. To increase its diagnostic potential, it may also transmit the data from a few bunch crossings (BXes) preceding or following the BX, in which the L1 trigger was generated. The paper describes the technical concepts and solutions used in the OMTF DAQ system. The system is still under development. However, it successfully passed the first tests.

Technicolor represents a viable alternative to the Higgs mechanism for generating gauge boson masses. Searches for technicolor particles $\rho_T$ and $\pi_T$ have been performed in the data collected by the DELPHI experiment at LEP at centre-of-mass energies between 192 and 208 GeV corresponding to an integrated luminosity of 452 pb $^{-1}$ . Good agreement is observed with the SM expectation in all channels studied. This is translated into an excluded region in the $(M_{\pi_T},M_{\rho_T})$ plane. The $\rho_T$ production is excluded for all $90 < M_{\rho_T}<206.7$ GeV/c $^2$ . Assuming a point-like interaction of the $\pi_T$ with gauge bosons, an absolute lower limit on the charged $\pi_T$ mass at 95% CL is set at 79.8 GeV/c $^2$ , independently of other parameters of the technicolor model.

The pseudoscalar meson ηb has been searched for in two-photon interactions at LEP II. The data sample corresponds to a total integrated luminosity of 617 pb−1 at centre-of-mass energies ranging from 161 to 209 GeV. Upper limits at a confidence level of 95% on the product Γγγ(ηb)×BR(ηb) are 190, 470 and 660 eV/c2 for the ηb decaying into 4, 6 and 8 charged particles, respectively.

Bose-Einstein correlations (BEC) between final state particles in the reaction e+e- -&gt; W+W- -&gt; q_1 anti-q_2 q_3 anti-q_4 have been studied. Data corresponding to a total integrated luminosity of 550 pb^{-1}, recorded by the DELPHI detector at centre-of-mass energies ranging from 189 to 209 GeV, were analysed. An indication for inter-W BEC between like-sign particles has been found at the level of 2.4 standard deviations of the combined statistical and systematic uncertainties.

Events are analyzed in which a high transverse momentum proton was produced at polar angles of 10°, 20° and 45°. The experiment was performed with the Split Field Magnet detector at the CERN ISR at $$\sqrt s $$ =62 GeV. A 4-jet structure of these events is found [1]. The measured charge structure of spectator jets is compatible with proton production from hard diquark scattering. This is supported by a study of baryon number compensation in the towards jets. The observed charge compensation in the towards jets suggests dominance of hard (ud) scattering. Evidence forΔ ++ production at high transverse momentum indicates the presence of an additional (uu) scattering component. The properties of the recoiling away jets are compatible with the fragmentation of a valence quark and/or of a gluon as in the case of meson triggers.

In a high-statistics experiment at the CERN-ISR we analyze the variation of the average transverse momentum in fixed rapidity intervals as a function of the multiplicity density of charged particles produced in proton-proton collisions at √s = 31, 44 and 62 GeV. The average transverse momentum depends on both rapidity y and charged multiplicity density, ρ = Δn/Δy. The dependence on ρ changes gradually from an increase at low y, constancy at intermediate y and decrease at large y.

High energy proton-proton interactions yielding a single trigger particle with large transverse momentum give rise to a four-jet event structure with two transverse jets and two jets along the beam direction. The transverse jets are due to the fragmentation of point like scattered partons. It is shown that the quantum numbers of triggering charged pions and positive kaons are correlated with the flavour of the scattered parent parton; thus one can enhance data samples with a particular flavour of a scattered parton. The analysis, which is independent of detailed model calculations, exploits (a) the identification of the leading particles in the trigger jets (trigger particles), (b) the measurement of their relative production rates, (c) short range quantum number correlations within the trigger jets, and (d) long range correlations between leading particles from different jets. The data were obtained at $$\sqrt s $$ =62 GeV with the Split Field Magnet detector at the CERN ISR.

Many-particle rapidity correlations have been studied for αα,dd, andpp interactions at the CERN Intersecting Storage Rings using the Split-Field Magnet detector, and basing the investigating on the distributions of rapidity gaps between particles. In the framework of a simple cluster model, it is found that all the data samples have similar features and that the events contain clusters of two different types.

Events obtained by triggering on a single particle with high transverse momentump T show a four-jet structure. The two transverse jets are due to the fragmentation of point-like scattered partons. Experimental evidence is presented that highp T K − mesons and their associated jets are produced by hard scattering and subsequent fragmentation of flavour neutral partons with a rather soft structure function. Hence, gluons are a natural source of highp T K − mesons which do not share any valence quark with the incoming protons. The analysis is based upon measurements of short-range quantum number correlations within the trigger jet and of long-range correlations between different jets. The data were obtained at $$\sqrt s$$ =62 GeV GeV with the Split Field Magnet Detector (SFM) at the CERN ISR.

A search for pair-produced charged Higgs bosons was performed in the high energy data collected by the DELPHI detector at LEP II at centre-of-mass energies from 189 GeV to 202 GeV. The three different final states, \tau \nu \tau \nu, c \bar s \bar c s and c \bar s \tau \nu were considered. New methods were applied to reject wrong hadronic jet pairings and for the tau identification, where a discriminator based on tau polarisation and polar angles was used. No excess of data compared to the expected Standard Model processes was observed and the existence of a charged Higgs boson with mass lower than 71.5 GeV/c^2 is excluded at the 95% confidence level.

We have measured the inclusive cross section for the reaction π−n→pX−− at 21, 205 and 360 GeV/c in the kinematic region |tnp|<1.0 (GeV/c)2. The differential cross sections can be described qualitatively by the reggeized one-pion-exchange amplitude at all momenta studied; however, there is evidence for the contribution of other amplitudes. The extracted π−π− total cross section for 4⪅sππ⪅340 GeV2 is of the order of 10–12 mb. The average number of charged particles and dispersion of the charged particle multiplicity distributions for various sππ intervals are compatible with results observed in hadron-proton interactions.

The charmed strange baryon Ξ 0 c was searched for in the decay channel Ξ 0 c → Ξ -π + , and the beauty strange baryon Ξ b in the inclusive channel Ξ b → Ξ -ℓ -νX, using the 3.5 million hadronic Z events collected by the DELPHI experiment in the years 1992-1995.The Ξ -was reconstructed through the decay Ξ -→ Λπ -, using a constrained fit method for cascade decays.An iterative discriminant analysis was used for the Ξ 0 c and Ξ b selection.The production rates were measured to be f Ξ 0 c ×BR(Ξ 0 c → Ξ -π + ) = (4.7 ± 1.4(stat.)± 1.1(syst.))× 10 -4 per hadronic Z decay, and BR(b → Ξ b )×BR(Ξ b → Ξ -ℓ -X) = (3.0 ± 1.0(stat.)± 0.3(syst.))× 10 -4 for each lepton species (electron or muon).The lifetime of the Ξ b baryon was measured to be τ Ξ b = 1.45 +0.55 -0.43 (stat.)± 0.13(syst.)ps.A combination with the previous DELPHI lifetime measurement gives τ Ξ b = 1.48 +0.40 -0.31 (stat.)± 0.12(syst.)ps.

Measurements are presented of short range three-particle rapidity correlation in pp interactions at c.m. energies [Formula: see text], 44 and 62 GeV. The data were obtained at the CERN Intersecting Storage Rings (ISR) using the Split Field Magnet Detector (SFM) with a minimum bias trigger. Three-particle short range rapidity correlations are observed for the (-+-) and (+-+) combinations; no short-range correlation is observed for the (---) and (+++) configurations. The rapidity range of the three-particle correlations is approximately the same as for the two-particle correlations.

Inclusive cross sections forΔ ++ production inpp interactions at different ISR energies are presented. The differential cross sectiondσ/dx forΔ ++ production is found to be approximately independent of Feynmanx. No strong energy dependence is seen over the ISR energy range. The topological cross sections ofΔ ++ at $$\sqrt s = 62$$ GeV show an appreciable contribution from non-diffractive production mechanisms. An upper limit for theΔ 0 production cross section is determined.

Measurements are presented of inclusive charged particle production in proton-proton collisions at √s=31, 44 and 62 GeV at the CERN ISR. The large acceptance of the Split Field Magnet detector allows a single experimental setup to cover almost the full longitudinal phase space up to a transverse momentum of 3 GeV/c.

The total punchthrough probability of showers produced by negatively charged pions of momenta 30, 40, 50, 75, 100, 200 and 300 GeV/c, has been measured in the RD5 experiment at CERN using a toroidal spectrometer. The range of the measurement extends to 5.3 m of equivalent iron. Our results have been obtained by two different analysis methods and are compared with the resutls of a previous experiment.

Data are presented on pomeron-pomeron interactions which produce a central π+π−π+π− system in proton-proton collisions at √s=62 GeV at the CERN Intersecting Storage Rings. A spin-parity analysis of the π+π−π+π− system shows evidence for the production of the statef 2 (1720) with decay to ρ0π+π−. Since pomeron-pomeron interactions are expected to favor the production of gluonic bound states, observation of thef 2 (1720) supports earlier interpretations of it as a glueball. In addition, enhancements near threshold give indication of the statef 2 (1270) decaying to ρ0ρ0 and the statef 0 (1400) decaying to ρ0π+π−.

We report on measurements of charged pion production cross sections at θ ≅ 50°, pT ≅ 3–9 GeV/c and √s = 45 GeV, taken with the Split Field Magnet Detector at the CERN Intersecting Storage Rings (ISR). Together with previous data at √s = 62 GeV, this allows the calculation of the exponent n assuming a power law dependence pnT. Values of n ≈ 8 are found at low xT = 2pT/√s which drop to about 7 at xT ≈ 0.3. The measured values of π+/π− rise with xT and approach ≈ 2 at xT ≈ 0.3. A first-order QCD calculations is reasonably consistent with the data.

Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb−1. No evidence for a signal was found. Limits on the energy scale Λ, were set for scalar-, vector- and tensor-like coupling scenarios.

This paper describes firmware architecture of a new part of muon trigger system of the CMS detector – one of four detectors installed along LHC accelerator in CERN. Overlap Muon Track Finder (OMTF) is a new trigger subsystem designed to work in difficult barrel-endcap region of CMS detector. OMTF is designed to receive data from different detector types and process it to select 3 best muon candidates. These muon candidates are then forwarded to Global Muon Trigger (GMT). Performance requirements demanded usage of custom designed hardware. All the data reception and processing takes part in modern, large FPGA device. The IPBus module allows easy firmware control and diagnostics via Ethernet connection.

The contribution of single diffraction dissociation to highp T particle production has been determined with the split field magnet detector. For transverse momentap T >2 GeV/c and production angles θ>10° it is found to be less than 5% for all types of trigger particles. Specifically, a diffractive origin of the large production cross section for highp T protons can be excluded. The contributions found to highp T production are found to be in good agreement with extrapolations of the relative particle yields from single diffraction dissociation observed in inelastic minimum bias events.

Deep inelastic proton-proton collisions have been recorded with the Split-Field-Magnet Detector (SFM) at the CERN Intersecting Storage Rings (ISR) by triggering on a single particle at high transverse momentum. Full reconstruction of the charged particles in these collisions was performed. In this paper we demonstrate the existence of a structure comprised of four jet-like clusters, two longitudinal and two transverse with respect to the beam, as would be expected from hard scattering of proton constituents.

Differential production cross sections have been measured for ${\ensuremath{\Sigma}}^{\mathrm{\ensuremath{-}}}$, ${\ensuremath{\Xi}}^{\mathrm{\ensuremath{-}}}$, ${\ensuremath{\Omega}}^{\mathrm{\ensuremath{-}}}$, ${\ensuremath{\Sigma}}^{+}$, \ensuremath{\Sigma}${\ifmmode\bar\else\textasciimacron\fi{}}^{+}$, and \ensuremath{\Xi}${\ifmmode\bar\else\textasciimacron\fi{}}^{+}$ relative to pion production at several ${x}_{F}$ and ${P}_{T}$ with 0.24${\mathrm{eqx}}_{F}$${P}_{T}$using 400-GeV protons incident on a Cu target. The data can be described by the , where A and n depend only on the hyperon type, and B is quadratic in ${x}_{F}$, and also depends on hyperon type. Comparison with previous experiments supports scaling in ${x}_{F}$ over the range 200--400 GeV/c.

We have studied π−d interactions at 21 GeV/c with charged multiplicities of 9 or more. Cross sections, single-particle distributions and two-particle correlations are discussed. The evidence for double scattering effects is confirmed and analysed.

Interactions in which the baryon is emitted forwards in the c.m.s. are studied in 8 and 16 GeV/c π+p collisions. These interactions are interpreted as representing baryon exchange. The properties of such off-shell NN annihilation events are studied. It is found that the multiplicity distribution of the multi-pion system as a function of the effective mass for events with |upp| < 1 GeV2 is the same as for real NN annihilations.

The quark model does not exclude states composed of more than three quarks, like pentaquark systems. Controversial evidence for such states has been published in the last years, in particular: for a strange pentaquark Θ(1540)+; for a double-strange state, the Ξ(1862)−−, subsequently called Φ(1860)−−; and for a charmed state, the Θc(3100)0. If confirmed, a full pentaquark family might exist; such pentaquark states could be produced in e+e− annihilations near the Z energy. In this Letter a search for pentaquarks is described using the DELPHI detector at LEP, characterized by powerful particle identification sub-systems crucial in the separation of the signal from the background for these states. At 95% CL, upper limits are set on the production rates 〈N〉 of such particles and their charge-conjugate state per Z decay: 〈NΘ+〉×Br(Θ+→pKS0)<5.1×10−4, 〈NΘ++〉<1.6×10−3, 〈NΦ(1860)−−〉×Br(Φ(1860)−−→Ξ−π−)<2.9×10−4, 〈NΘc(3100)0〉×Br(Θc(3100)0→D∗+p¯)<8.8×10−4.

The CMS muon system is conceived for trigger and muon track reconstruction. The redundancy and robustness of the system are guaranteed by three complementary subsystems: drift tube in the barrel, cathode strip chamber in the end-cap and resistive plate chamber in barrel and end-cap. The installation of muon stations and read-out trigger electronic has been completed in middle 2007. Since than, a remarkable effort has been addressed to the detector commissioning in order to ensure the readiness of the hardware/software chain for the LHC start up operation. At the end of 2007, a test of an entire CMS slice has been performed, involving about 5% of muon stations. Several thousand cosmic muons events have been collected. Performance of the barrel chambers are reported.

The production of ρ(770)0,K *(892)0, $$\bar K^* (892)^0 $$ andf 2(1270) mesons as leading particles in hadron jets (<z>∼0.7) has been measured in deep inelasticpp interactions at the CERN ISR at $$\sqrt s = 62$$ GeV. The comparison of vector and pseudoscalar meson production at the same transverse momentum provides a rather model independent way to determine the fragmentation parameterV/P. We determine(V/P) u,d =1.66±0.18±0.63 from the ρ/π ratio and(V/P) s =0.90±0.13±0.27 from theK */K ratio. For thef 2(1270) production we findf 2/ρ0=0.30±0.08.

The density of charged particles near a single highp T trigger particle in proton-proton collisions has been studied with the SFM detector at the CERN-ISR. It is shown that:—the secondaries cluster in a jet-like manner about the trigger particle; —the momentum distributions in this trigger jet can be unambiguously separated from the spectator background distributions;—the momentum distributions in this trigger jet can be unambiguously separated from the spectator background distributions;—the momentum component transverse to the jet direction is exponentially damped;—the width of the transverse distributions increases with the momentum component along the jet;—the fractional longitudinal momentum density depends strongly on the trigger transverse momentum and scales with $$x_T = {{2p_T } \mathord{\left/ {\vphantom {{2p_T } {\sqrt s }}} \right. \kern-\nulldelimiterspace} {\sqrt s }}$$ . All these findings support the hard constituent scattering origin of highp T hadrons.

An analysis of 1650 stars induced by 9.4 GeV/c deuterons in a nuclear emulsion is presented. Multiplicity and angular distributions of secondaries are discussed.

The study of quark jets in e+e− reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However, our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo simulations with JETSET (with and without Bose–Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (≲2GeV/c2) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.

A search for the pair production of fourth generation b’-quarks was performed using data taken by the DELPHI detector at LEP-II. The analysed data were collected at centre-of-mass energies ranging from 196 to 209 GeV, corresponding to an integrated luminosity of 420 pb-1. No evidence for a signal was found. Upper limits on BR(b’→bZ) and BR(b’→cW) were obtained for b’ masses ranging from 96 to 103 GeV/c 2. These limits, together with the theoretical branching ratios predicted by a sequential four generations model, were used to constrain the value of $R_{\text{CKM}}=|\frac{V_{cb\prime}}{V_{\text{tb}\prime}V_{tb}}|$ , where Vcb′, Vtb′ and Vtb are elements of the extended CKM matrix.

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: A_{FB}^b (89.449 GeV) = 0.0637 \pm 0.0143(stat.) \pm 0.0017(syst.) A_{FB}^b (91.231 GeV) = 0.0958 \pm 0.0032(stat.) \pm 0.0014(syst.) A_{FB}^b (92.990 GeV) = 0.1041 \pm 0.0115(stat.) \pm 0.0024(syst.) Combining these results yields the b-quark pole asymmetry A_{FB}^{b,0} = 0.0972 \pm 0.0030(stat.) \pm 0.0014(syst.)

The Resistive Plate Chambers [M. Abbrescia, et al., Nucl. Instr. and Meth. A 550 (2005) 116] are used in the CMS experiment [CMS Collaboration, The CMS experiment at the CERN LHC 2008, J. Inst. 3 (2008) S08004] as a dedicated muon trigger both in barrel and endcap system. About 4000m2 of double gap RPCs have been produced and have been installed in the experiment since more than one and half Years. The full barrel system and a fraction of the endcaps have been monitored to study dark current behaviour and system stability, and have been extensively commissioned with Cosmic Rays collected by the full CMS experiment.

Measurements of the Ξ− and Ξ¯+ masses, mass differences, lifetimes and lifetime differences are presented. The Ξ¯+ sample used is much larger than those used previously for such measurements. In addition, the Ξ production rates in Z→bb¯ and Z→qq¯ events are compared and the position ξ∗ of the maximum of the ξ distribution in Z→qq¯ events is measured.

Gluon scattering processes are studied in hadronic highp T events using data obtained with the Split Field Magnet detector (SFM) at the CERN ISR. The experimental set-up allowed the scanning of a wide range of parton energies and scattering angles. It is shown that for positive pions as trigger particles, the parton composition of the recoil jet is correlated with the polar angle and transverse momentum of the triggering pion. Over the kinematical region studied, the recoil jet originates predominantly from scatered gluons, with an increasing prevalence of the gluon component towards forward triggering angles. The variation of the momentum structure of the recoil jet with the trigger angle indicates that the fragmentation function of gluons is softer than that of quarks.

Production of jets with fast leading fragments has been studied in deep inelastic proton-proton interactions using the Split Field Magnet detector at the CERN ISR. The kinematics of the underlying parton processes is determined on an event-by-event basis. Parton scattering amplitudes are extracted for scattering angles, Θ∗, in the interval −0.4 < cos Θ∗ < 0.9. The data which are known to be dominated by quark gluon scattering, agree with predictions from lowest order QCD, while e.g. an abelian theory can be excluded.

The production of wrong sign charmed mesons b→D(s)X, D(s)=(D0,D+,Ds), is studied using the data collected by the DELPHI experiment in the years 1994 and 1995. Charmed mesons in Z→bb̄ events are exclusively reconstructed by searching for the decays D0→K−π+, D+→K−π+π+ and Ds+→φπ+→K+K−π+. The wrong sign contribution is extracted by using two discriminant variables: the charge of the b-quark at decay time, estimated from the charges of identified particles, and the momentum of the charmed meson in the rest frame of the b-hadron. The inclusive branching fractions of b-hadrons into wrong sign charm mesons are measured to be: B(b→D0X)+B(b→D−X)=(9.3±1.7(stat)±1.3(syst)±0.4(B))%, B(b→Ds−X)=(10.1±1.0(stat)±0.6(syst)±2.8(B))% where the first error is statistical, the second and third errors are systematic.

Measurements of Zγ* production are presented using data collected by the DELPHI detector at centre-of-mass energies ranging from 183 to 209 GeV, corresponding to an integrated luminosity of about 667 pb-1. The measurements cover a wide range of the possible final state four-fermion configurations: hadronic and leptonic (e+e-qq̄, μ+μ-qq̄, qq̄νν̄), fully leptonic (l+l-l’+l’-) and fully hadronic final states (qq̄qq̄, with a low mass qq̄ pair). Measurements of the Zγ* cross-section for the various final states have been compared with the Standard Model expectations and found to be consistent within the errors. In addition, a total cross-section measurement of the l+l-l’+l’- cross-section is reported, and found to be in agreement with the prediction of the Standard Model.

Double-tagged interactions of photons with virtualities Q2 between 10 GeV2 and 200 GeV2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated luminosity of 550 pb-1. The γ*γ*→μ+μ- data agree with QED predictions. The cross-section of the reaction γ*γ*→hadrons is measured and compared to the LO and NLO BFKL calculations.

The Muon System of the CMS experiment at CERN employees three different detector technologies—Drift Tube Chambers (DT) in the barrel part, Cathode Strip Chambers (CSC) in the endcaps and Resistive Plate Chambers (RPC) both in the barrel and the endcaps. TDs and CSCs serve as precise muon trajectory measurement devices. The RPCs are responsible for the bunch crossing identification and for a fast muon transverse momentum measurement. The total number of RPCs is 480 in the barrel and 756 in the endcaps, covering an area of about 3500 square meters. A brief overview of the system will be presented as well as some recent results about the system stability and performance.