Petar Adzic

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today’s technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.

We review the physics opportunities of the Future Circular Collider, covering its e+e-, pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the synergy and complementarity of the different colliders, which will contribute to a uniquely coherent and ambitious research programme, providing an unmatchable combination of precision and sensitivity to new physics.

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.

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.

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Searches for the Standard Model Higgs boson have been performed in the data collected by the DELPHI experiment at LEP in the year 2000 at centre-of-mass energies between 200 and 209 GeV corresponding to a total integrated luminosity of 224 pb−1. No evidence for a Higgs signal is observed in the kinematically accessible mass range, and a 95% CL lower mass limit of 114.3 GeV/c2 is set, to be compared with an expected median limit of 113.5 GeV/c2 for these data.

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.

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.

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%.

An analysis of the data collected in 1997 and 1998 with the DELPHI detector at e+e− collision energies close to 183 and 189 GeV was performed in order to extract the hadronic and leptonic fermion-pair cross-sections, as well as the leptonic forward–backward asymmetries and angular distributions. The data are used to put limit on contact interactions between fermions, the exchange of R-parity violating SUSY sneutrinos, Z′ bosons and the existence of gravity in extra dimensions.

The amplitude of the signal collected from the PbWO4 crystals of the CMS electromagnetic calorimeter is reconstructed by a digital filtering technique. The amplitude reconstruction has been studied with test beam data recorded from a fully equipped barrel supermodule. Issues specific to data taken in the test beam are investigated, and the implementation of the method for CMS data taking is discussed.

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.

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.

Infrared and collinear safe event shape distributions and their mean values are determined using the data taken at five different centre of mass energies above MZ with the DELPHI detector at LEP. From the event shapes, the strong coupling αs is extracted in O(αs2), NLLA and a combined scheme using hadronisation corrections evaluated with fragmentation model generators as well as using an analytical power ansatz. Comparing these measurements to those obtained at MZ, the energy dependence (running) of αs is accessible. The logarithmic energy slope of the inverse strong coupling is measured to bedα−1sdlog(Ecm)=1.39±0.34(stat)±0.17(syst),in good agreement with the QCD expectation of 1.27.

The value of the b quark mass at the MZ scale defined in the MS renormalization scheme, mb(MZ), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI detector to bemb(MZ)=2.67±0.25(stat.)±0.34(frag.)±0.27(theo.)GeV/c2.The analysis considers NLO corrections to the three-jet production rate including mass effects, and the result obtained agrees with the QCD prediction of having a running b quark mass at an energy scale equal to MZ. This is the first time that such a measurement is performed far above the bb production threshold. The study also verifies the flavour independence of the strong coupling constant for b and light quarks within 1% accuracy.

In 1996 LEP ran at a centre-of-mass energy of 161 GeV, just above the threshold of W-pair production. DELPHI accumulated data corresponding to an integrated luminosity of 9.93 pb−1, and observed 29 events that are considered as candidates for W-pair production. From these, a cross-section for the doubly resonant e+e− → WW process of 3.67−0.85+0.97 ± 0.19 pb has been measured. Within the Standard Model, this cross-section corresponds to a mass of the W-boson of 80.40 ± 0.44 (stat.) ± 0.09 (syst.) ± 0.03 (LEP) GeV/c2. Alternatively, if mW is held fixed at its current value determined by other experiments, the observed cross-section is used to obtain limits on trilinear WWV (V ≡ γ, Z) couplings.

Using D∗+ mesons exclusively reconstructed in the DELPHI detector at LEP, an excess of 66±14(stat.) events is observed in the D∗+π+π− final state with a mass of 2637±2(stat.)±6(syst.) MeV/c2 and a full width smaller than 15 MeV/c2 (95% C.L.). This signal is compatible with the expected decay of a radially excited D∗′ (JP=1−) meson.

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.

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 response of the CMS barrel calorimeter (electromagnetic plus hadronic) to hadrons, electrons and muons over a wide momentum range from 2 to 350 GeV/c has been measured. To our knowledge, this is the widest range of momenta in which any calorimeter system has been studied. These tests, carried out at the H2 beam-line at CERN, provide a wealth of information, especially at low energies. The analysis of the differences in calorimeter response to charged pions, kaons, protons and antiprotons and a detailed discussion of the underlying phenomena are presented. We also show techniques that apply corrections to the signals from the considerably different electromagnetic (EB) and hadronic (HB) barrel calorimeters in reconstructing the energies of hadrons. Above 5 GeV/c, these corrections improve the energy resolution of the combined system where the stochastic term equals 84.7±1.6% and the constant term is 7.4±0.8%. The corrected mean response remains constant within 1.3% rms.

A sample of 2.2 million hadronic Z decays, selected from the data recorded by the Delphi detector at Lep during 1994–1995 was used for an improved measurement of inclusive distributions of $\pi^+, K^+$ and p and their antiparticles in gluon and quark jets. The production spectra of the individual identified particles were found to be softer in gluon jets compared to quark jets, with a higher multiplicity in gluon jets as observed for inclusive charged particles. A significant proton enhancement in gluon jets is observed indicating that baryon production proceeds directly from colour objects. The maxima, $\xi^*$ , of the $\xi$ -distributions for kaons in gluon and quark jets are observed to be different.

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.

Using a 252Cf neutron source we have calibrated the response of Ge detectors to fast neutrons and deduced the expression for determination of the flux of fast environmental neutrons based on the intensity of the spectral structure at 691.3 keV. We also suggest an approximate expression for estimation of the flux of environmental thermal neutrons from the intensity of the 139.9 keV line.

Performance tests of some aspects of the CMS ECAL were carried out on modules of the "barrel" sub-system in 2002 and 2003. A brief test with high energy electron beams was made in late 2003 to validate prototypes of the new Very Front End electronics. The final versions of the monitoring and cooling systems, and of the high and low voltage regulation were used in these tests. The results are consistent with the performance targets including those for noise and overall energy resolution, required to fulfil the physics programme of CMS at the LHC.

Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated.

A new precise measurement of |Vcb| and of the branching ratio BR(B̄0→D∗+ℓ−ν̄ℓ) has been performed using a sample of about 5000 semileptonic decays B̄0→D∗+ℓ−ν̄ℓ, selected by the DELPHI detector at LEP I by tagging the soft pion from D∗+→D0π+. The results are: Vcb=(39.0±1.5(stat.)+2.5−2.6(syst. exp.)±1.3(syst. th.))×10−3, BR(B̄0→D∗+ℓ−ν̄ℓ)=(4.70±0.13(stat.)+0.36−0.31(syst. exp.))%. The analytic dependencies of the differential cross-section and of the Isgur–Wise form factor as functions of the variable w=vB0·vD∗ have also been obtained by unfolding the experimental resolution.

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.

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.

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.

A search for events with one jet and at most one isolated lepton used data taken at LEP-2 by the DELPHI detector. These data were accumulated at a center-of-mass energy of 183 GeV and correspond to an integrated luminosity of 47.7 pb−1. Production of single scalar and vector leptoquarks was searched for. Limits at 95% confidence level were derived on the masses (ranging from 134GeV/c2 to 171GeV/c2 for electromagnetic type couplings) and couplings of the leptoquark states. A search for top-charm flavour changing neutral currents (e+e−→t̄c or charge conjugate) used the semileptonic decay channel. A limit on the flavour changing cross-section via neutral currents was set at 0.55pb (95% confidence level).

The hadronic structure of the decay of the τ lepton to three charged particles, τ→3πντ, is studied using data collected by the DELPHI detector at LEP between 1992 and 1995. The invariant mass of the 3π system, m3π, is fitted using the models of Kühn and Santamaria, Isgur, Morningstar and Reader, and Feindt. The 3π and π+π− mass spectra are compared with each model. Below m3π2=2.3GeV2, all are in good qualitative agreement. Above m3π2=2.3GeV2, anomalous behaviour is observed, consistent with the existence of a hitherto unseen decay mode of the τ through a radial excitation of the a1 meson.

Measurements of the trilinear gauge boson couplings WWgamma and WWZ are presented using the data taken by DELPHI in 1998 at a centre-of-mass energy of 189 GeV and combined with DELPHI data at 183 GeV. Values are determined for Delta(g_1^Z) and Delta(kappa_gamma), the differences of the WWZ charge coupling and of the WWgamma dipole coupling from their Standard Model values, and for lambda_gamma, the WWgamma quadrupole coupling. A measurement of the magnetic dipole and electric quadrupole moment of the W is extracted from the results for Delta(kappa_gamma) and lambda_gamma. The study uses data from the final states jjlv, jjjj, lX, jjX and gammaX, where j represents a quark jet, l an identified lepton and X missing four-momentum. The observations are consistent with the predictions of the Standard Model.

Trilinear gauge boson couplings are measured using data taken by DELPHI at 161 GeV and 172 GeV. Values for WWV couplings (V=Z,γ) are determined from a study of the reactions e+e−→W+W− and e+e−→Weν, using differential distributions from the WW final state in which one W decays hadronically and the other leptonically, and total cross-section data from other channels. Limits are also derived on neutral ZVγ couplings from an analysis of the reaction e+e−→γ+invisibleparticles.

Inclusive charged hadron distributions as obtained from the DELPHI measurements at 130, 136, 161, 172 and 183 GeV are presented as a function of the variables rapidity, ξp, p and transversal momenta. Data are compared with event generators and with MLLA calculations, in order to examine the hypothesis of local parton hadron duality. The differential momentum spectra show an indication for coherence effects in the production of soft particles. The relation between the energy dependence of the charged multiplicity and the rapidity distribution is examined.

The total and the differential cross sections for the reaction e+e− → γγ(γ) have been measured with the DELPHI detector at LEP using an integrated luminosity of 36.9 pb−1. The results agree with the QED predictions and consequently there is no evidence for non-standard channels with the same experimental signature. The lower limits obtained on the QED cutoff parameters are Λ+ > 143 GeV and Λ− > 120 GeV, and the lower bound on the mass of an excited electron with an effective coupling constant λγ = 1 is 132 GeV/c2. Upper limits on the branching ratios for the decays Z0 → γγ, Z0 → π0γ, Z0 → ηγ and Z0 → γγγ have been determined to be 5.5 × 10−5, 5.5 × 10−5, 8.0 × 10−5, and 1.7 × 10−5 respectively. All the limits are at the 95% confidence level.

Ensuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.

A search for stable and long-lived heavy charged particles used the data taken by the DELPHI experiment at energies from 130 to 183 GeV. The Cherenkov light detected in the Ring Imaging Cherenkov Detector and the ionization loss measured in the Time Projection Chamber identify heavy particles from masses of 2 to nearly 89 GeV/c2. Upper limits are given on the production cross-section and masses of sleptons, free squarks with a charge of q=±23e and hadronizing squarks.

Higgs bosons predicted by the fermiophobic scenario within Two Higgs Doublets Models were searched for in the data collected by the DELPHI detector at centre-of-mass energies between 189 GeV and 202 GeV, corresponding to a total integrated luminosity of 380 pb−1. No signal was found and confidence limits were derived in the framework of possible extensions of the Standard Model Higgs sector.

The ratio of the CKM quark-mixing matrix elements |Vub|/|Vcb| has been measured using B hadron semileptonic decays. The analysis uses the reconstructed mass M_X of the secondary hadronic system produced in association with an identified lepton. Since B -> X_u lepton anti-nu transitions are characterised by hadronic masses below those of the D mesons produced in B -> X_c lepton anti-nu transitions, events with a reconstructed value of M_X significantly below the D mass are selected. Further signal enrichments are obtained using the topology of reconstructed decays and hadron identification. A fit to the numbers of decays in the b -> u enriched and depleted samples with M_X above and below 1.6 GeV/c^2 and to the shapes of the lepton energy distribution in the B rest frame gives |Vub|/|Vcb|= 0.103^{+0.011}_{-0.012} (stat.) +/- 0.016 (syst.) +/- 0.010 (model) and, correspondingly, a charmless semileptonic B decay branching fraction of BR(B -> X_u lepton anti-nu) = (1.57 +/- 0.35 (stat.) +/- 0.48 (syst.) +/- 0.27 (model)) x 10^{-3}.

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.

Decays of W± bosons, produced at LEP2, have been used to measure the |Vcs| element of the Cabibbo-Kobayashi-Maskawa matrix. Values for |Vcs| were extracted both from the measured hadronic branching ratio of W± decays and by tagging the flavour of hadronic jets produced in W± decays. Applying the two methods to the data collected during 1996 at energies of 161 and 172 GeV, DELPHI obtains |Vcs|=0.91+0.15−0.14(stat)±0.05(syst).

Measurements of the trilinear gauge boson couplings WWγ and WWZ are presented from data taken by DELPHI in 1997 at an energy of 183 GeV. From a study of the reactions e+e−→W+W−, e+e−→Weν and e+e−→ννγ, values are obtained for Δg1Z and Δκγ, the differences of the WWZ charge coupling and of the WWγ dipole couplings from their Standard Model values, and for λγ, the WWγ quadrupole coupling. The observations are consistent with the predictions of the Standard Model.

DELPHI results are presented on the inclusive production of the neutral mesons ρ0, f0(980), f2(1270), K∗02(1430) and f′2(1525) in hadronic Z0 decays. They are based on about 2 million multihadronic events collected in 1994 and 1995, using the particle identification capabilities of the DELPHI Ring Imaging Cherenkov detectors and measured ionization losses in the Time Projection Chamber. The total production rates per hadronic Z0 decay have been determined to be: 1.19±0.10 for ρ0; 0.164±0.021 for f0(980); 0.214±0.038 for f2(1270); 0.073±0.023 for K∗02(1430); and 0.012±0.006 for f′2(1525). The total production rates for all mesons and differential cross-sections for the ρ0, f0(980) and f2(1270) are compared with the results of other LEP experiments and with models.

A search for the Higgs boson in final states with one, two or three isolated photons has been performed based on data taken at LEP 2 by the DELPHI detector. The data analysed correspond to a total integrated luminosity of 67.5 pb−1 at centre-of-mass energies of 161 GeV (9.7 pb−1), 172 GeV (10.1 pb−1) and 183 GeV (47.7 pb−1). No evidence for the processes e+e−→Hγ with H→bb̄ or γγ and e+e−→Hqq̄ with H→γγ was observed. Model-independent limits on σ(e+e−→Hγ)×BR(H→bb̄), σ(e+e−→Hqq̄)×BR(H→γγ) and σ(e+e−→Hγ)×BR(H→γγ) are set, as well as model-dependent limits on Higgs boson anomalous couplings to vector bosons.

The present note relies on the recently published conceptual design report of the LHeC and extends the first contribution to the European strategy debate in emphasising the role of the LHeC to complement and complete the high luminosity LHC programme. The brief discussion therefore focuses on the importance of high precision PDF and alpha_s determinations for the physics beyond the Standard Model (GUTs, SUSY, Higgs). Emphasis is also given to the importance of high parton density phenomena in nuclei and their relevance to the heavy ion physics programme at the LHC.

The performance of electromagnetic calorimeter modules made of proton-irradiated PbWO4 crystals has been studied in beam tests. The modules, similar to those used in the Endcaps of the CMS electromagnetic calorimeter (ECAL), were formed from 5×5 matrices of PbWO4 crystals, which had previously been exposed to 24 GeV protons up to integrated fluences between 2.1× 1013 and 1.3× 1014 cm−2. These correspond to the predicted charged-hadron fluences in the ECAL Endcaps at pseudorapidity η = 2.6 after about 500 fb−1 and 3000 fb−1 respectively, corresponding to the end of the LHC and High Luminosity LHC operation periods. The irradiated crystals have a lower light transmission for wavelengths corresponding to the scintillation light, and a correspondingly reduced light output. A comparison with four crystals irradiated in situ in CMS showed no significant rate dependence of hadron-induced damage. A degradation of the energy resolution and a non-linear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The latter is interpreted, through comparison with simulation, as a side-effect of the degradation in light transmission. The experimental results obtained can be used to estimate the long term performance of the CMS ECAL.

The cross-section for the process e+e- -> W+W- has been measured with the data sample collected by DELPHI at an average centre-of-mass energy of 189 GeV and corresponding to an integrated luminosity of 155 pb^{-1}. Based on the 2392 events selected as WW candidates, the cross-section for the doubly resonant process e+e- -> W+W- has been measured to be 15.83 +- 0.38 (stat) +- 0.20 (syst) pb. The branching fractions of the W decay were also measured and found to be in good agreement with the Standard Model expectation. From these a value of the CKM mixing matrix element |V_{cs}| = 1.001 +- 0.040 (stat) +- 0.020 (syst) was derived.

A search for stable and long-lived heavy charged particles was performed using the data taken by the DELPHI experiment at an energy of 189 GeV. The Cherenkov light detected in the Ring Imaging Cherenkov Detector and the ionisation loss measured in the Time Projection Chamber were used to identify heavy particles passing through the detector. No evidence for the production of such particles has been found, therefore exclusion limits at 95% confidence level were derived on the masses of left and right handed smuons and staus. The results were combined with previous DELPHI searches in this channel. Including previous DELPHI results, masses of left (right) handed stable smuons and staus can be excluded between 2 GeV/c2 and 88 (87.5) GeV/c2 at 95% CL.

The DELPHI detector at LEP has collected 54 pb^{-1} of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e+e- -> b bbar events, <n>_{bb}, and the difference delta_{bl} between <n>_{bb} and the multiplicity, <n>_{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself.

Searches for pair production of supersymmetric particles under the assumption that R-parity is not conserved are presented, based on data recorded by the DELPHI detector in 1998 from e+e- collisions at a centre-of-mass energy of 189 GeV. Only one R-parity violating LL\bar{E} term (i.e. one lambda coupling), which couples scalar leptons to leptons, is considered to be dominant at a time. Moreover, it is assumed that the strength of the R-parity violating couplings is such that the lifetimes can be neglected. The search for pair production of neutralinos, charginos and sleptons has been performed for both direct R-parity violating decays and indirect cascade decays. The results are in agreement with Standard Model expectations, and are used to update the constraints on the MSSM parameter values and the mass limits previously derived at sqrt(s) = 183 GeV. The present 95% C.L. limits on supersymmetric particle masses are: m_{\tilde{\chi}^0} > 30 GeV/c^2 and m_{\tilde{\chi}^\pm} > 94 GeV/c^2; m_{\tilde{\nu}} > 76.5 GeV/c^2 (direct and indirect decays); m_{\tilde{\ell}_R} > 83 GeV/c^2 (indirect decay only).

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)%.

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.

From data corresponding to an integrated luminosity of 53.5pb−1 taken during the 183GeV run in 1997, DELPHI has measured the W mass from direct reconstruction of WW→ℓν̄qq̄ and WW→qq̄qq̄ events. Combining these channels, a value of mW=80.238±0.154(stat)±0.035(syst)±0.035(fsi)±0.021(LEP)GeV/c2 is obtained, where fsi denotes final state interaction. Combined with the W mass obtained by DELPHI from the WW production cross-section and with the direct measurement at 172 GeV this leads to a measured value of mW=80.270±0.137(stat)±0.031(syst)±0.030(fsi)±0.021(LEP)GeV/c2, in good agreement with the Standard Model expectation. The width of the W boson is also measured, giving the value ΓW=2.48±0.40(stat)±0.10(syst)GeV/c2.

A search for the production of the η′c meson, the first radial excitation of the ground state of charmonium ηc(2980), in the photon–photon fusion reaction at LEP has been performed using the data collected by the DELPHI detector during 1992–1996. No evidence of η′c production is found in the mass region 3520–3800 MeV/c2. An upper limit for the ratio of the two-photon widths of the η′c and ηc is obtained.

The rate Z→bb̄bb̄ was measured using about 2×106 hadronic decays collected by the DELPHI experiment in 1994 and 1995. Events were forced into 3-jets with ymin>0.06 and a b-tag was required for every jet. The rate was measured to be: R4b=BR(Z→bb̄bb̄)BR(Z→hadrons)=(6.0±1.9(stat.)±1.4(syst.))×10−4 where the invariant mass of every bb̄ system is above twice the b quark mass. Using the value of R4b the probability of secondary production of a bb̄ pair from a gluon per hadronic Z decay, gbb, was extracted and found to be: gbb=(3.3±1.0(stat.)±0.8(syst.))×10−3.

A study of b semileptonic decays into D, Dπ± and D∗π± final states is presented. The D0, D+ and D∗+ mesons are exclusively reconstructed in Z decay data recorded from 1992 to 1995 in the DELPHI experiment at LEP. The overall branching fractions are measured to be:BR(b→D0ℓ−ν̄ℓX)=(7.04±0.34(stat)±0.36(syst.exp)±0.17(BRD))%,BR(b→D+ℓ−ν̄ℓX)=(2.72±0.19(stat)±0.16(syst.exp)±0.18(BRD))%,BR(b→D∗+ℓ−ν̄ℓX)=(2.75±0.17(stat)±0.13(syst.exp)±0.09(BRD))%,where the D0 and D+ results include also contributions from D∗0 and D∗+ decays. A fit to the distribution of the π± impact parameter to the primary interaction vertex provides a measurement of the b semileptonic branching fractions into the D0π±X, D+π±X and D∗+π±X final states. Assuming that single pion decay modes of B mesons dominate, the partial rates for B̄→Dπℓ−νℓ̄ and B̄→D∗πℓ−νℓ̄ have been obtained, corresponding to a total branching fraction:BR(B̄→Dπℓ−νℓ̄)+BR(B̄→D∗πℓ−νℓ̄)=(3.40±0.52(stat)±0.32(syst))%.This result agrees well with the observed difference between the total B semileptonic branching fraction and the sum of the B̄→Dℓ−νℓ̄ and D∗ℓ−νℓ̄ branching fractions.

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.

B 0d meson oscillations are measured in hadronic Z0 decays using the charge of a lepton or the mean charge of an event hemisphere to sign the presence of a b or a b̄ quark when it is produced, and using the charge of a lepton emitted at large pt or of a D*± to sign the presence of a B or a B̄ meson when it decays. With 3.2 million hadronic Z0 decays registered by DELPHI between 1991 and 1994, the mass difference Δm d between the two physical B 0d states is measured in four channels: Taking into account the statistical overlap between these measurements and the common systematic uncertainties, the combined result is:

A test of the QED process e+e−→γγ(γ) is reported. The data analysed were collected with the DELPHI detector in 1998 and 1999 at the highest energies achieved at LEP, reaching 202 GeV in the centre-of-mass. The total integrated luminosity amounts to 375.7 pb−1. The differential and total cross-sections for the process e+e−→γγ were measured, and found to be in agreement with the QED prediction. 95% confidence level (C.L.) lower limits on the QED cut-off parameters of Λ+>330 GeV and Λ−>320 GeV were derived. A 95% C.L. lower bound on the mass of an excited electron of 311 GeV/c2 (for λγ=1) was obtained. s-channel virtual graviton exchange was searched for, resulting in 95% C.L. lower limits on the string mass scale, MS: MS>713 GeV/c2 (λ=1) and MS>691 GeV/c2 (λ=−1).

The longitudinal polarization of the Λb baryon is measured at the LEP e+e− collider by DELPHI. It is determined from the charged lepton and neutrino energy spectra in 249±19 Λb semileptonic decays reconstructed in ≈3.5 million hadronic Z0 decays using Λ0-lepton correlations. The measured polarization is: PΛb=−0.49−0.30+0.32(stat.)±0.17(syst.)

A measurement of the W mass and width has been performed by the DELPHI collaboration using the data collected during 1998. The data sample has an integrated luminosity of 155 pb^{-1} and an average centre-of-mass energy of 188.6 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- -> lvqq and W+W- -> qqqq channels. The W mass result for the 1998 data set is M_W = 80.387 +/- 0.087 (stat) +/- 0.034 (syst) +/- 0.017 (LEP) +/- 0.035 (FSI) GeV/c2, where FSI represents the uncertainty due to final state interaction effects in the qqqq channel, and LEP represents that arising from the knowledge of the beam energy of the accelerator. Combining this result with those previously published by the DELPHI collaboration gives the result M_W = 80.359 +/- 0.074 (stat) +/- 0.032 (syst) +/- 0.017 (LEP) +/- 0.033 (FSI) GeV/c2. The combined value for the W width is \Gamma_W = 2.266 +/- 0.176 (stat) +/- 0.056 (syst) +/- 0.052 (FSI) GeV/c2.

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.

Searches for supersymmetric partners of top and bottom quarks are presented using data taken by the DELPHI experiment at LEP in 1997 and 1998. No deviations from standard model expectations are observed in these data sets, which are taken at centre-of-mass energies of 183 GeV and 189 GeV and correspond to integrated luminosities of 54 pb−1 and 158 pb−1. These results are used in combination with those obtained by DELPHI at lower centre-of-mass energies to exclude regions in the squark–neutralino mass plane at 95% confidence level.

The branching ratio for the leptonic decay of charged B mesons (B−→τ−ν̄τ) has been measured using selected leptonic τ−→ℓ−ντν̄ℓ and hadronic τ−→ντX decays in Z→bb̄ decays recorded by DELPHI at LEP1 in 1992–1995. The result, BR(B−→τ−ν̄τ)<1.1×10−3 at the 90% confidence level, is consistent with standard model expectations and puts a constraint on the ratio tanβ/MH±<0.46 (GeV/c2)−1 in the framework of models with two Higgs doublets (type II Higgs doublet model). From the missing energy distribution in Z→bb̄ decays without identified leptons, the b→τν̄τX branching ratio has been measured in the hadronic channel τ→ντX′. The result, BR(b→τν̄τX)=(2.19±0.24(stat)±0.39(syst))%, is consistent with the Standard Model prediction and with previous experimental measurements.

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.

The total and the differential cross-sections for the reaction e+e−→γγ(γ) have been measured with the DELPHI detector at LEP at centre-of-mass energies from 130 to 183 GeV for an integrated luminosity of 78.19 pb−1. The results agree with the QED predictions. The lower limits (obtained including previously published results at the Z0 energies) on the QED cutoff parameters are Λ+>253 GeV and Λ−>225 GeV and the lower bound on the mass of an excited electron with an effective coupling constant λγ=1 is 231 GeV/c2. All the limits are at the 95% confidence level.

An update of the searches for charginos and neutralinos is presented, based on a data sample corresponding to the 53.9 pb−1 recorded by the DELPHI detector in 1997, at a centre-of-mass energy of 183 GeV. No evidence for a signal was found. The lower mass limits are 4–5 GeV/c2 higher than those obtained at a centre-of-mass energy of 172 GeV. The (μ,M2) domain excluded by combining the neutralino and chargino searches implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 29.1 GeV/c2 for tanβ≥ 1.

Analysis of the rapidity structure of charge correlations in hadronic events from Z0 decays gives evidence for chain-like charge-ordering of particle production along the thrust axis, as predicted by ‘QCD-motivated’ string-like fragmentation models.

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.

Abstract A prototype of the safety system for the electromagnetic calorimeter (ECAL) of the CMS detector at LHC has been implemented and tested in Super Modules SM0 and SM1 during the ECAL test-beam campaign in summer 2003. The aim was to examine the system performance thoroughly and to resolve several open issues regarding the final system design. The performed tests mainly focused on the readout system performance, its calibration and noise problems. Furthermore, irradiation tests of the readout electronics components with a 64 MeV proton beam up to an equivalent cumulative dose of 200 kGy and 3.2×10 14 neutron cm −2 have been performed at the Paul Scherrer Institute in spring 2004. The results of all these tests are very promising, leading to the conclusion that the tested prototype offers an excellent basis for the development of the safety system for the entire CMS ECAL.

The DELPHI experiment at LEP has measured the inclusive charmless B hadron decay branching ratio, the B branching ratio into two charmed particles, and the total number of charmed particles per B decay, using the hadronic Z data taken between 1992 and 1995. The results are extracted from a fit to the b-tagging probability distribution based on the precise impact parameter measurements made using the microvertex detector. The inclusive charmless B branching ratio, including B decays into hidden charm (cc̄), is measured to be 0.033±0.021. The B branching ratio into two open charmed particles is 0.136±0.042. The mean number of charmed particles per B decay (including hidden charm) is 1.147±0.041. After subtracting the B decay branching ratio into hidden charm, the charmless B branching ratio is found to be 0.007±0.021, compatible with the Standard Model expectation. Models that predict an additional contribution to the charmless B branching ratio of 0.037 or higher are excluded with at least 95% confidence.

Searches for charginos, neutralinos and sleptons at LEP2 centre-of-mass energies from 130 GeV to 189 GeV have been used to set lower limits on the mass of the Lightest Supersymmetric Particle and other supersymmetric particles within the MSSM framework. R-parity conservation has been assumed. The lightest neutralino was found to be heavier than 32.3 GeV/c^2 independent of the m_0 value. The lightest chargino, the second-to-lightest neutralino, the next-to-heaviest neutralino, the heaviest neutralino, the sneutrino and the right-handed selectron were found to be heavier than 62.4 GeV/c^2, 62.4 GeV/c^2, 99.9 GeV/c^2, 116.0 GeV/c^2, 61.0 GeV/c^2, and 87.0 GeV/c^2, respectively. These limits do not depend on m_0 or M_2 and are valid for 1 \leq tan(beta) \leq 40, in the mu region where the lightest neutralino is the LSP. If the sneutrino is heavier than the chargino the lightest neutralino has to be heavier than 32.4 GeV/c^2. The effects of mixings in the third family of sfermions on these limits are discussed. The confidence level of all limits given is 95%.

Production of Σ− and Λ(1520) in hadronic Z decays has been measured using the Delphi detector at Lep. The Σ− is directly reconstructed as a charged track in the Delphi microvertex detector and is identified by its Σ→nπ decay leading to a kink between the Σ− and π-track. The reconstruction of the Λ(1520) resonance relies strongly on the particle identification capabilities of the barrel Ring Imaging Cherenkov detector and on the ionisation loss measurement of the TPC. Inclusive production spectra are measured for both particles. The production rates are measured to be〈NΣ−/NZhad〉=0.081±0.002±0.010,〈NΛ(1520)/NZhad〉=0.029±0.005±0.005.The production rate of the Λ(1520) suggests that a large fraction of the stable baryons descend from orbitally excited baryonic states. It is shown that the baryon production rates in Z decays follow a universal phenomenological law related to isospin, strangeness and mass of the particles.

Searches for spontaneous R-parity-violating signals at s=183 GeV and s=189 GeV have been performed using the 1997 and 1998 DELPHI data, under the assumption of R-parity breaking in the third lepton family. The expected topology for the decay of a pair of charginos into two acoplanar taus plus missing energy was investigated and no evidence for a signal was found. The results were used to derive a limit on the chargino mass and to constrain the allowed domains of the MSSM parameter space.

This document provides a brief overview of the recently published report on the design of the Large Hadron Electron Collider (LHeC), which comprises its physics programme, accelerator physics, technology and main detector concepts. The LHeC exploits and develops challenging, though principally existing, accelerator and detector technologies. This summary is complemented by brief illustrations of some of the highlights of the physics programme, which relies on a vastly extended kinematic range, luminosity and unprecedented precision in deep inelastic scattering. Illustrations are provided regarding high precision QCD, new physics (Higgs, SUSY) and electron-ion physics. The LHeC is designed to run synchronously with the LHC in the twenties and to achieve an integrated luminosity of O(100) fb$^{-1}$. It will become the cleanest high resolution microscope of mankind and will substantially extend as well as complement the investigation of the physics of the TeV energy scale, which has been enabled by the LHC.

The 4-jet events collected by the DELPHI experiment at LEP1 in 1992, 1993 and 1994 are analysed to determine the contribution of the triple-gluon vertex. Two of the four jets are tagged as jets from b- or c-quarks using lifetime and lepton transverse momentum information. The 4-jet contributions from double-gluon bremsstrahlung, the triple-gluon vertex, and secondary quark-antiquark pair production then yield significantly different two-dimensional distributions in the generalized Nachtmann Reiter angle versus the opening angle of the two secondary jets. These distributions are used to fit CACF, the ratio of the coupling strength of the triple-gluon vertex to that of gluon bremsstrahlung, and NCNA, the ratio of the number of quark colours to the number of gluons, giving CACF = 2.51 ± 0.28 and NCNA = 0.38 ± 0.10 in agreement with the values expected from QCD: CACF = 94 = 2.25 and NCNA = 38 = 0.375.

A search for pair produced charged Higgs bosons has been performed in the high energy data collected by DELPHI at LEP with s=161, 172 and 183 GeV. The analysis uses the τντν, cs̄τν and cs̄c̄s final states and a combination of event shape variables, di-jet masses and jet flavour tagging for the separation of a possible signal from the dominant W+W− and QCD backgrounds. The number of selected events has been found to be compatible with the expected background. The lower excluded value of the H± mass obtained by varying the H±→ hadrons decay branching ratio has been found to be 56.3 GeV/c2.

The data collected by DELPHI in 1998 at the centre-of-mass energy of 189 GeV have been used to update the search for charginos nearly mass-degenerate with the lightest supersymmetric particle, which is assumed to be the lightest neutralino. Mass differences below ΔM=3 GeV/c2 are considered. No excess of events with respect to the Standard Model expectation has been observed, and exclusions in the plane of ΔM versus chargino mass are given. The new ΔM independent lower limit on the mass of the chargino is 62.4 GeV/c2 in the higgsino scenario (which includes the gaugino mass unification scenario), if all sfermions are heavier than the lightest chargino. In the approximation of large sfermion masses the limit is 59.8 GeV/c2, independently of the field content.

The cross sections for the production of single charged and neutral intermediate vector bosons were measured using integrated luminosities of 52 pb–1 and 154 pb–1 collected by the experiment at centre-of-mass energies of 182.6 GeV and 188.6 GeV, respectively. The cross sections for the reactions were determined in limited kinematic regions. The results found are in agreement with the Standard Model predictions for these channels.

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.

Multiplicity fluctuations in rings around the jet axis and in off-axis cones have been measured by the DELPHI collaboration in e+e− annihilations into hadrons at LEP energies. The measurements are compared with analytical perturbative QCD calculations for the corresponding multiparton system, using the concept of Local Parton Hadron Duality. Some qualitative features are confirmed by the data but substantial quantitative deviations are observed.

An update of the searches for charginos and gravitinos is presented, based on a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.

DELPHI results are presented on the inclusive production of two (KKπ)0 states in the mass region 1.2–1.6 GeV/c2 in hadronic Z decays at LEP I. The measured masses (widths) are 1274±6 MeV/c2 (29±12 MeV/c2) and 1426±6 MeV/c2 (51±14 MeV/c2), respectively. A partial-wave analysis of the (KKπ)0 system shows that the first peak is consistent with the IG(JPC)=0+(1++)/(0−+)a0(980)π and the second with the IG(JPC)=0+(1++)K∗(892)K+c.c. assignments. The total hadronic production rates per hadronic Z decay are (0.165±0.051) and (0.056±0.012), respectively. These measurements are consistent with the two states being the f1(1285) and f1(1420) mesons.

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.

This paper presents the current architecture of the control and safety systems designed and implemented for the Electromagnetic Calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). An evaluation of system performance during all CMS physics data taking periods is reported, with emphasis on how software and hardware solutions are used to overcome limitations, whilst maintaining and improving reliability and robustness. The outcomes of the CMS ECAL Detector Control System (DCS) Software Analysis Project were a fundamental step towards the integration of all control system applications and the consequent piece-by-piece software improvements allowed a smooth transition to the latest revision of the system. The ongoing task of keeping the system in-line with new hardware technologies and software platforms specified by the CMS DCS Group is discussed. The structure of the comprehensive support service with detailed incident logging is presented in addition to a complete test setup for reproducing failures and for testing solutions prior to deployment into production. A correlation between the acquired experience, the development of new software tools and a reduction in the DCS support load is highlighted.

This paper presents results on charged Higgs boson production, based on LEP data collected at s=172 GeV, that complement the previous DELPHI results obtained at centre of mass energies up to 161 GeV. The charged Higgs bosons are assumed to be pair produced and to decay either into a quark pair or into τντ. The three different possible final states are included in the analysis. Data from ring imaging Cherenkov and microvertex detectors are used to identify the quarks as a cs pair. The number of candidates found is compatible with the background expected from standard processes. Combining the results of the present analysis with those of the previous analysis at lower energies, a new lower mass limit for the charged Higgs boson is set at 54.5 GeV/c2.

The main goal of this work is to establish the nuclear decay scheme of $^{76}\mathrm{Sr}$ and energy levels of its doubly odd daughter nucleus $^{76}\mathrm{Rb}$. The extremely neutron deficient nucleus $^{76}\mathrm{Sr}$ lying at the N=Z (=38) line with half-life of 8.9 s was produced in spallation reactions of 600 MeV protons from the CERN Synchrocyclotron (SC) with a Nb multifoil target in conjunction with a W surface ionization source at the ISOLDE facility. The \ensuremath{\gamma}-spectroscopy measurements have been performed with two Ge detectors which were positioned at about \ifmmode\pm\else\textpm\fi{}30\ifmmode^\circ\else\textdegree\fi{} respectively downstream to the $^{76}\mathrm{Sr}$ beam. The obtained singles and coincidence \ensuremath{\gamma} spectra were used to determine energies and intensities of \ensuremath{\gamma} lines assigned to the decay of $^{76}\mathrm{Sr}$ and to establish some details of the nuclear level configuration of its daughter nucleus $^{76}\mathrm{Rb}$ up to 1000 keV.

Measurements of on-shell ZZ production are described, using data collected by DELPHI in 1997 and 1998, at centre-of-mass energies s=182.6 GeV and 188.6 GeV, respectively. Results obtained in each of the final states qq̄qq̄, μ+μ−qq̄, e+e−qq̄, νν̄qq̄, l+l−l+l−, and νν̄l+l− are presented. The measured cross-sections for on-shell ZZ production via the tree-level doubly-resonant graphs (NC02) are: σNC02 (182.6 GeV)=0.38±0.18 (stat)±0.04 (syst) pb, σNC02 (188.6 GeV)=0.60±0.13 (stat)±0.07 (syst) pb. They are consistent with the Standard Model expectations of 0.25 and 0.65 pb at each energy.

A search for the supersymmetric partner of the goldstino, the sgoldstino S, at LEP2 is presented. The production Sγ followed by S decay into two gluons or into two photons was studied at 189–202 GeV LEP centre-of-mass energies. No evidence for the S production was found and limits on the S mass corresponding to different theory parameters are given.

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.