Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, eta, and full azimuth, phi, as a function of charged particle multiplicity and particle transverse momentum, p(T). In high-multiplicity events, a long-range (2 < vertical bar Delta eta vertical bar < 4), near-side (Delta phi approximate to 0) structure emerges in the two-particle Delta eta-Delta phi correlation functions. This is the first observation of such correlations in proton-nucleus collisions, resembling the ridge-like correlations seen in high-multiplicity pp collisions at root s = 7 TeV and in AA collisions over a broad range of center-of-mass energies. The correlation strength exhibits a pronounced maximum in the range of p(T) = 1-1.5 GeV/c and an approximately linear increase with charged particle multiplicity for high-multiplicity events. These observations are qualitatively similar to those in pp collisions when selecting the same observed particle multiplicity, while the overall strength of the correlations is significantly larger in pPb collisions. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved

A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17.3 fb(-1), collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the ZZ channel, where both Z bosons decay to e or μ pairs, is 126.2 ± 0.6(stat) ± 0.2(syst) GeV. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis.

decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B 0 ? m 1 m 2 decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B 0 s and B 0 mesons and lead to further improvements in the precision of these crucial tests of the standard model.Experimental particle physicists have been testing the predictions of the standard model of particle physics (SM) with increasing precision since the 1970s. Theoretical developments have kept pace by improving the accuracy of the SM predictions as the experimental results gained in precision. In the course of the past few decades, the SM has passed critical tests derived from experiment, but it does not address some profound questions about the nature of the Universe. For example, the existence of dark matter, which has been confirmed by cosmological data 3 , is not accommodated by the SM. It also fails to explain the origin of the asymmetry between matter and antimatter, which after the Big Bang led to the survival of the tiny amount of matter currently present in the Universe Fig. 1c, is forbidden at the elementary level because the Z 0 cannot couple directly to quarks of different flavours, that is, there are no direct 'flavour changing neutral currents'. However, it is possible to respect this rule and still have this decay occur through 'higher order' transitions such as those shown in Fig. 1d and e. These are highly suppressed because each additional interaction vertex reduces their probability of occurring significantly. They are also helicity and CKM suppressed. Consequently, the branching fraction for the B 0 s ?m z m { decay is expected to be very small compared to the dominant b antiquark to c antiquark transitions. The corresponding decay of the B 0 meson, where a d quark replaces the s quark, is even more CKM suppressed because it requires a jump across two quark generations rather than just one.The branching fractions, B, of these two decays, accounting for higher-order electromagnetic and strong interaction effects, and using lattice quantum chromodynamics to compute the B 8,9 , such as in the diagrams shown in Fig. 1f and g, that can considerably modify the SM branching fractions. In particular, theories with additional Higgs bosons 10,11 predict possible enhancements to the branching fractions. A significant deviation of either of the two branching fraction measurements from the SM predictions would give insight on how the SM should be extended. Alternatively, a measurement compatible with the SM could provide strong constraints on BSM theories. . Both CMS and LHCb later ...

A search for new physics is performed in multijet events with large missing transverse momentum produced in proton-proton collisions at √ s = 8 TeV using a data sample corresponding to an integrated luminosity of 19.5 fb −1 collected with the CMS detector at the LHC. The data sample is divided into three jet multiplicity categories (3-5, 6-7, and ≥8 jets), and studied further in bins of two variables: the scalar sum of jet transverse momenta and the missing transverse momentum. The observed numbers of events in various categories are consistent with backgrounds expected from standard model processes. Exclusion limits are presented for several simplified supersymmetric models of squark or gluino pair production. 3 Sample selectionAll these backgrounds are determined using the data, with as little reliance on simulation as possible. The CMS detector and event reconstructionThe CMS detector is a multipurpose apparatus, described in detail in Ref. [5]. The CMS coordinate system is defined with the origin at the centre of the detector and the z axis along the anticlockwise beam direction. The polar angle θ is measured with respect to the z axis, and the azimuthal angle φ (measured in radians) in the plane perpendicular to that axis. Chargedparticle trajectories are measured with a silicon pixel and strip tracker, covering |η| < 2.5, where the pseudorapidity η is defined as η = − ln[tan(θ/2)]. Immersed in the 3.8 T magnetic field provided by a 6 m diameter superconducting solenoid, which also encircles the calorimeters, the tracking system provides transverse momentum (p T ) resolution of approximately 1.5% for charged particles with p T ∼ 100 GeV. A lead-tungstate crystal electromagnetic calorimeter and a brass-and-scintillator hadron calorimeter surround the tracking volume and cover the region |η| < 3. Steel and quartz-fibre hadron forward calorimeters extend the coverage to |η| ≤ 5. Muons are identified in gas ionization detectors embedded in the steel flux return yoke of the magnet. The events used for this search are recorded using a two-level trigger system described in Ref. [5].The recorded events are required to have at least one well-identified interaction vertex with z position within 24 cm from the nominal centre of the detector and transverse distance from the z axis less than 2 cm. The primary vertex is the one with the largest sum of p T -squared of all the associated tracks, and is assumed to correspond to the hard-scattering process. The events are reconstructed using a particle-flow (PF) algorithm [23]. This algorithm reconstructs a list of particles in each event, namely charged and neutral hadrons, photons, muons, and electrons, combining the information from the tracker, the calorimeters, and the muon system. These particles are then clustered into jets using the anti-k T clustering algorithm [24] with a size parameter of 0.5. Contributions from additional pp collisions overlapping with the event of interest (pileup) are mitigated by discarding charged particles not associated with the primary vert...

A search for supersymmetry is presented based on multijet events with large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of ffiffi ffi s p ¼ 13 TeV. The data, corresponding to an integrated luminosity of 35.9 fb −1 , were collected with the CMS detector at the CERN LHC in 2016. The analysis utilizes four-dimensional exclusive search regions defined in terms of the number of jets, the number of tagged bottom quark jets, the scalar sum of jet transverse momenta, and the magnitude of the vector sum of jet transverse momenta. No evidence for a significant excess of events is observed relative to the expectation from the standard model. Limits on the cross sections for the pair production of gluinos and squarks are derived in the context of simplified models. Assuming the lightest supersymmetric particle to be a weakly interacting neutralino, 95% confidence level lower limits on the gluino mass as large as 1800 to 1960 GeV are derived, and on the squark mass as large as 960 to 1390 GeV, depending on the production and decay scenario.