In this Letter we report the first results on $\pi^\pm$, K$^\pm$, p and $\mathrm {p\overline{p}}$ production at mid-rapidity ($\left|y\right|<0.5$) in central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, measured by the ALICE experiment at the LHC. The $p_{\rm T}$ distributions and yields are compared to previous results at $\sqrt{s_{\rm NN}}$ = 200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with $\sqrt{s_{\rm NN}}$, which in hydrodynamic models is expected as a consequence of the increasing particle density. While the ${\rm K}/\pi$ ratio is in line with predictions from the thermal model, the ${\rm p}/\pi$ ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.

The production of ${\rm\Xi}^-$ and ${\rm\Omega}^-$ baryons and their anti-particles in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV has been measured using the ALICE detector. The transverse momentum spectra at mid-rapidity ($|y| < 0.5$) for charged $\rm\Xi$ and $\rm\Omega$ hyperons have been studied in the range $0.6 < p_{\rm T} < 8.0$ GeV/$c$ and $1.2 < p_{\rm T} < 7.0$ GeV/$c$, respectively, and in several centrality intervals (from the most central 0-10% to the most peripheral 60-80% collisions). These spectra have been compared with the predictions of recent hydrodynamic models. In particular, the Krak${\'o}$w and EPOS models give a satisfactory description of the data, with the latter covering a wider $p_{\rm T}$ range. Mid-rapidity yields, integrated over $p_{\rm T}$, have been determined. The hyperon-to-pion ratios are similar to those at RHIC: they rise smoothly with centrality up to $\langle N_{\rm part}\rangle$~150 and saturate thereafter. The enhancements (yields per participant nucleon relative to pp collisions) increase both with the strangeness content of the baryon and with centrality, but are less pronounced than at lower energies.

The jet fragmentation function and transverse profile for jets with 25 GeV < ptJet < 500 GeV and etaJet<1.2 produced in proton-proton collisions with a center-of-mass energy of 7 TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb^-1. Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. None of these choices reproduce both the transverse profile and fragmentation function over the full kinematic range of the measurement.

The production of Kshort and Lambda hadrons is studied in inelastic pp collisions at sqrt(s) = 0.9 and 7 TeV collected with the ATLAS detector at the LHC using a minimum-bias trigger. The observed distributions of transverse momentum, rapidity, and multiplicity are corrected to hadron level in a model-independent way within well defined phase-space regions. The distribution of the production ratio of Lambdabar to Lambda baryons is also measured. The results are compared with various Monte Carlo simulation models. Although most of these models agree with data to within 15% in the Kshort distributions, substantial disagreements with data are found in the Lambda distributions of transverse momentum.

Results of three searches are presented for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons, e or mu. The analysis uses a data sample collected during the first half of 2011 that corresponds to a total integrated luminosity of 1 fb^-1 of sqrt{s} = 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. Opposite-sign and same-sign dilepton events are separately studied, with no deviations from the Standard Model expectation observed. Additionally, in opposite- sign events, a search is made for an excess of same-flavour over different-flavour lepton pairs. Effective production cross sections in excess of 9.9 fb for opposite-sign events containing supersymmetric particles with missing transverse momentum greater than 250 GeV are excluded at 95% CL. For same-sign events containing supersymmetric particles with missing transverse momentum greater than 100 GeV, effective production cross sections in excess of 14.8 fb are excluded at 95% CL. The latter limit is interpreted in a simplified weak gaugino production model excluding chargino masses up to 200 GeV.

We report measurements of the production of prompt D$^0$, D$^+$, D$^{*+}$ and D$^+_{\rm s}$ mesons in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV, in the centrality classes 0-10%, 30-50% and 60-80%. The D-meson production yields are measured at mid-rapidity ($|y|<0.5$) as a function of transverse momentum ($p_{\rm T}$). The $p_{\rm T}$ intervals covered in central collisions are: $1<p_{\rm T}<50$ Gev/$c$ for D$^0$, $2<p_{\rm T}<50$ GeV/$c$ for D$^+$, $3<p_{\rm T}<50$ GeV/$c$ for D$^{*+}$, and $4<p_{\rm T}<16$ GeV/$c$ for D$^+_{\rm s}$ mesons. The nuclear modification factors ($R_{\rm AA}$) for non-strange D mesons (D$^0$, D$^+$, D$^{*+}$) show minimum values of about 0.2 for $p_{\rm T}$ = 6-10 GeV/$c$ in the most central collisions and are compatible within uncertainties with those measured at $\sqrt{s_{\rm NN}}=2.76$ TeV. For D$^+_{\rm s}$ mesons, the values of $R_{\rm AA}$ are larger than those of non-strange D mesons, but compatible within uncertainties. In central collisions the average $R_{\rm AA}$ of non-strange D mesons is compatible with that of charged particles for $p_{\rm T} > 8$ GeV/$c$, while it is larger at lower $p_{\rm T}$. The nuclear modification factors for strange and non-strange D mesons are also compared to theoretical models with different implementations of in-medium energy loss.

Inclusive distributions of charged particles in hadronic W decays are experimentally investigated using the statistics collected by the DELPHI experiment at LEP during 1997, 1998 and 1999, at centre-of-mass energies from 183 to around 200 GeV. The possible effects of interconnection between the hadronic decays of two Ws are not observed. Measurements of the average multiplicity for charged and identified particles in q qbar and WW events at centre-of-mass energies from 130 to 200 GeV and in W decays are presented. The results on the average multiplicity of identified particles and on the position xi^* of the maximum of the xi_p = -log(2p/sqrt(s)) distribution are compared with predictions of JETSET and MLLA calculations.

Infrared and collinear safe event shape distributions and their mean values are determined in e+e- collisions at centre-of-mass energies between 45 and 202 GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, alpha_s is extracted from the mean values and shapes. In an alternative approach, renormalisation group invariance (RGI) is used as an explicit constraint, leading to a consistent description of mean values without the need for sizeable power corrections. The QCD beta-function is precisely measured using this approach. From the DELPHI data on Thrust, including data from low energy experiments, one finds beta_0 = 7.86 +/- 0.32 for the one loop coefficient of the beta-function or, assuming QCD, n_f = 4.75 +/- 0.44 for the number of active flavours. These values agree well with the QCD expectation of beta_0=7.67 and n_f=5. A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5 GeV.

A measurement of the underlying activity in scattering processes with a hard scale in the several GeV region is performed in proton-proton collisions at sqrt(s) = 0.9 and 7 TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity |eta| < 2 and transverse momentum pT > 0.5 GeV/c is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. A significant growth of the average multiplicity and scalar-pT sum of the particles in the transverse region is observed with increasing pT of the leading track-jet, followed by a much slower rise above a few GeV/c. For track-jet pT larger than a few GeV/c, the activity in the transverse region is approximately doubled with a centre-of-mass energy increase from 0.9 to 7 TeV. Predictions of several QCD-inspired models as implemented in PYTHIA are compared to the data.

The spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7 TeV. The K^0_s, Lambda, and Xi^- particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum. The results are compared to other experiments and to predictions of the PYTHIA Monte Carlo program. The transverse momentum distributions are found to differ substantially from the PYTHIA results and the production rates exceed the predictions by up to a factor of three.