Yields of prompt and non-prompt J/psi, as well as Y(1S) mesons, are measured by the CMS experiment via their dimuon decays in PbPb and pp collisions at sqrt(sNN) = 2.76 TeV for quarkonium rapidity |y|<2.4. Differential cross sections and nuclear modification factors are reported as functions of y and transverse momentum pt, as well as collision centrality. For prompt J/psi with relatively high pt (6.5<pt<30 GeV/c), a strong, centrality-dependent suppression is observed in PbPb collisions, compared to the yield in pp collisions scaled by the number of inelastic nucleon-nucleon collisions. In the same kinematic range, a suppression of non-prompt J/psi, which is sensitive to the in-medium b-quark energy loss, is measured for the first time. Also the low-pt Y(1S) mesons are suppressed in PbPb collisions.

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.

We measured, with the KLOE detector, the spectrum of π+π− invariant mass in a sample of 6.7 × 105 e+e− → π+π−γ events with the photon at large polar angle (θγ > 45 ) at a centre of mass energy √ s around the φ mass. We observe in this spectrum a clear contribution from the intermediate process φ → f0(980)γ. A sizeable effect is also observed in the distribution of the pion forward-backward asymmetry. We use different theoretical models to fit the spectrum and we determine the f0 mass and coupling constants to the φ, to π +π− and to KK̄.

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.

The response of the combined CMS barrel calorimeters to hadrons, electrons and muons over a range from 2 to 350 GeV/c has been measured. The analysis of the differences in calorimeter response to charged pions, kaons, protons and antiprotons and a discussion of the underlying phenomena are presented. Techniques to correct the signals from the considerably different electromagnetic (EB) and hadronic (HB) barrel calorimeters in reconstructing the energies of hadrons are also presented. Above 5 GeV/c, these corrections improve the energy resolution of the combined system where the stochastic term equals 84.7% and the constant term is 7.4%. The corrected mean response remains constant within 1.3% rms.

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.

We have measured the ratio R S = Γ(KS → π π(γ))/Γ(KS → π π) with the KLOE detector at the DAΦNE ee collider. This measurement is fully inclusive with respect to the ππγ final state. The sample of over 10 two-pion decays of tagged KS mesons allows a statistical error as low as ∼ 0.1% to be obtained. The accuracy is limited by systematic uncertainties, which are estimated primarily from data. We find R S =2.236±0.003stat±0.015syst. The most recent measurement of R S = Γ(KS → π π)/Γ(KS → π π) dates back to 1976. The authors quote an accuracy of 4.3% [1]. This and other results of similar accuracy determine the current world-average value of R S, 2.197±0.026, the fractional error on which is 1.2%. Moreover, the averaging of the existing results is somewhat questionable, since the various experiments have not clearly described their procedures for handling radiative ππγ decays. It is currently of interest to improve the accuracy on R S, with particular attention to an accurate determination of what part of the radiative spectrum is included in the quoted result [2]. The validity of the ∆I = 1/2 rule, empirically established in K, Λ, Σ, and Ξ decays, has never been satisfactorily understood. This lack of understanding is closely connected with the difficulty in relating R(ǫ/ǫ) to the CKM matrix elements [3]. The value of R S also enters into the theoretical calculation for the ratio of branching ratios for the decays KL→μ μ and KL→π π [4]. We describe the first measurement of R S to achieve an accuracy below 1%,

We present a measurement of the K-π vector current form-factor parameters for the decay KL → πeν. We use 328 pb of data collected in 2001 and 2002, corresponding to ∼ 2 million Ke3 events. Measurements of semileptonic form factors provide information about the dynamics of the strong interaction and are necessary for evaluation of the phase-space integral Ie K needed to measure the CKM matrix element |Vus| for KL → πeν decays. Our result is λ+ = (28.6 ± 0.5 ± 0.4)10 for a linear fit, and λ+ = (25.5 ± 1.5 ± 1.0)10, λ + = (1.4 ± 0.7 ± 0.4)10 for a quadratic fit. key words: ke3 form factor PACS: 13.20.Eb

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.

KLOE has collected about 30 pb in year 2000 at the DAΦNE collider, which yields the largest population of φ meson radiative decays studied so far. We present the results obtained for φ → ηγ and φ → η′γ : the ratio of these two BR’s has been measured to be (5.3± 0.5 ± 0.3) · 10, leading to a very accurate determination of the mixing angle in the flavor basis φP = (40 +1.7 −1.5) ◦ and to the most accurate determination of BR(φ → η′γ ) to date: (6.8± 0.6 ± 0.5) · 10.

We have studied the Dalitz plot of the ee → ππγ events collected at √ s ≃ Mφ with the KLOE detector. In the dipion invariant mass (Mππ) region below 700 MeV, the process under study is dominated by the non-resonant process ee → ωπ with ω → πγ whereas, for higher Mππ values, the radiative φ decay to the f0(980) is the dominant mechanism. Different theoretical models are used to fit the Dalitz plot, taking also into account a possible contribution of the σ(600). For each model, we extract the f0(980) mass and its coupling to ππ, KK and to the φ.

We have searched for the decay K-S --> gamma gamma in a sample of similar to 2 x 10(9) phi --> KSKL decays collected at DA Phi NE with an integrated luminosity of 1.9 fb(-1). K-S are tagged by the K-L interaction in the calorimeter. Two prompt photons must also be detected. Kinematic constraints reduce the initial 6 x 10(5) events to 2740 candidates, from which a signal of 711 +/- 35 events is extracted. By normalizing to the K-S --> 2 pi(0) decays counted in the same sample, we measure BR (K-S --> gamma gamma) = (2.26 +/- 0.12(stat) +/- 0.06(syst)) x 10(-6), in agreement with O(p(4)) Chiral Perturbation Theory predictions.