Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (eta) and azimuthal angle (phi). Short-range correlations in Delta(eta), which are studied in minimum bias events, are characterized using a simple "independent cluster" parametrization in order to quantify their strength (cluster size) and their extent in eta (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb(-1) data set at 7TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate p(T) of 1-3 GeV/c, 2.0

Paramagnetic ultrasmall gadolinium oxide (Gd(2)O(3)) nanoparticles with particle diameters (d) of approximately 1 nm were synthesized by using three kinds of Gd(III) ion precursors and by refluxing each of them in tripropylene glycol under an O(2) flow. A large longitudinal relaxivity (r(1)) of water proton of 9.9 s(-1) mM(-1) was estimated. As a result, high contrast in vivo T(1) MR images of the brain tumor of a rat were observed. This large r(1) is discussed in terms of the huge surface to volume ratio (S/V) of the ultrasmall gadolinium oxide nanoparticles coupled with the cooperative induction of surface Gd(III) ions for the longitudinal relaxation of a water proton. It is found from the d dependence of r(1) that the optimal range of d for the maximal r(1), which may be used as an advanced T(1) MRI contrast agent, is 1-2.5 nm.

This paper presents a search for the pair production of top squarks in events with a single isolated electron or muon, jets, large missing transverse momentum, and large transverse mass. The data sample corresponds to an integrated luminosity of 19.5 fb −1 of pp collisions collected in 2012 by the CMS experiment at the LHC at a center-of-mass energy of √ s = 8 TeV. No significant excess in data is observed above the expectation from standard model processes. The results are interpreted in the context of supersymmetric models with pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. For small mass values of the lightest supersymmetric particle, top-squark mass values up to around 650 GeV are excluded.Published in the European Physical Journal C as doi:10.1140/epjc/s10052-013-2677-2. IntroductionThe standard model (SM) has been extremely successful at describing particle physics phenomena. However, it suffers from such shortcomings as the hierarchy problem, where fine-tuned cancellations of large quantum corrections are required in order for the Higgs boson to have a mass at the electroweak symmetry breaking scale of order 100 GeV [1][2][3][4][5][6]. Supersymmetry (SUSY) is a popular extension of the SM that postulates the existence of a superpartner for every SM particle, with the same quantum numbers but differing by one half-unit of spin. SUSY potentially provides a "natural", i.e., not fine-tuned, solution to the hierarchy problem through the cancellations of the quadratic divergences of the top-quark and top-squark loops. In addition, it provides a connection to cosmology, with the lightest supersymmetric particle (LSP), if neutral and stable, serving as a dark matter candidate in R-parity conserving SUSY models. This paper describes a search for the pair production of top squarks using the full dataset collected at √ s = 8 TeV by the Compact Muon Solenoid (CMS) experiment [7] at the Large Hadron Collider (LHC) during 2012, corresponding to an integrated luminosity of 19.5 fb −1 . This search is motivated by the consideration that relatively light top squarks, with masses below around 1 TeV, are necessary if SUSY is to be the natural solution to the hierarchy problem [8][9][10][11][12]. These constraints are especially relevant given the recent discovery of a particle that closely resembles a Higgs boson, with a mass of ∼125 GeV [13][14][15]. Searches for top-squark pair production have also been performed by the ATLAS Collaboration at the LHC in several final states [16][17][18][19][20], and by the CDF [21] and D0 [22] Collaborations at the Tevatron.The search presented here focuses on two decay modes of the top squark ( t): t → t χ 0 1 and t → b χ + . These modes are expected to have large branching fractions if kinematically allowed. Here t and b are the top and bottom quarks, and the neutralinos ( χ 0 ) and charginos ( χ ± ) are the mass eigenstates formed by the linear combination of the gauginos and higgsinos, which are the fermi...

A search for supersymmetry with R-parity conservation in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 inverse picobarns collected by the CMS experiment at the LHC. The search is performed in events with jets and significant missing transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary background, from standard model multijet production, is reduced by several orders of magnitude to a negligible level by the application of a set of robust kinematic requirements. With this selection, the data are consistent with the standard model backgrounds, namely t t-bar, W + jet and Z + jet production, which are estimated from data control samples. Limits are set on the parameters of the constrained minimal supersymmetric extension of the standard model. These limits extend those set previously by experiments at the Tevatron and LEP colliders

A search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at ffiffi ffi s p ¼ 8 TeV with the CMS detector at the LHC. The data set corresponds to an integrated luminosity of 19.7 fb −1 . In a search for narrow resonances that couple to quark-quark, quarkgluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 TeV. When interpreted in the context of specific models the limits exclude string resonances with masses below 5.0 TeV; excited quarks below 3.5 TeV; scalar diquarks below 4.7 TeV; W 0 bosons below 1.9 TeV or between 2.0 and 2.2 TeV; Z 0 bosons below 1.7 TeV; and Randall-Sundrum gravitons below 1.6 TeV. A separate search is conducted for narrow resonances that decay to final states including b quarks. The first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 TeV depending on their decay properties. Searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. The wide resonance search excludes axigluons and colorons with mass below 3.6 TeV, and color-octet scalars with mass below 2.5 TeV. Lower bounds between 5.0 and 6.3 TeV are set on the masses of quantum black holes.