Showing papers by "Kirika Uchida published in 2017"

Springer : Search for dark matter and unparticles in events with a Z boson and missing transverse momentum in proton-proton collisions at $ \sqrt{s}=13 $ TeV

Abstract: In the original paper, figure 10 was incorrect. The correct figure is shown below. Additionally, the unparticle entries in table 3, as well as figure 4 and 5 were labelled with incorrect values of ΛU.

Measurement of charged pion, kaon, and proton production in proton-proton collisions at √s = 13 TeV

Abstract: Transverse momentum spectra of charged pions, kaons, and protons are measured in proton-proton collisions at root s = 13 TeV with the CMS detector at the LHC. The particles, identified via their energy loss in the silicon tracker, are measured in the transverse momentum range of p(T) approximate to 0.1-1.7 GeV/c and rapidities vertical bar y vertical bar < 1. The pT spectra and integrated yields are compared to previous results at smaller ffiffiffi root s and to predictions of Monte Carlo event generators. The average pT increases with particle mass and charged particle multiplicity of the event. Comparisons with previous CMS results at root s = 0.9, 2.76, and 7 TeV show that the average pT and the ratios of hadron yields feature very similar dependences on the particle multiplicity in the event, independently of the center-of-mass energy of the pp collision.

Principal-component analysis of two-particle azimuthal correlations in PbPb and pPb collisions at CMS

Abstract: For the first time a principle-component analysis is used to separate out different orthogonal modes of the two-particle correlation matrix from heavy ion collisions. The analysis uses data from sNN=2.76TeV PbPb and sNN=5.02TeV pPb collisions collected by the CMS experiment at the CERN Large Hadron Collider. Two-particle azimuthal correlations have been extensively used to study hydrodynamic flow in heavy ion collisions. Recently it was shown that the expected factorization of two-particle results into a product of the constituent single-particle anisotropies is broken. The new information provided by these modes may shed light on the breakdown of flow factorization in heavy ion collisions. The first two modes (“leading” and “subleading”) of two-particle correlations are presented for elliptical and triangular anisotropies in PbPb and pPb collisions as a function of pT over a wide range of event activity. The leading mode is found to be essentially equivalent to the anisotropy harmonic previously extracted from two-particle correlation methods. The subleading mode represents a new experimental observable and is shown to account for a large fraction of the factorization breaking recently observed at high transverse momentum. The principle-component analysis technique was also applied to multiplicity fluctuations. These also show a subleading mode. The connection of these new results to previous studies of factorization is discussed.

Measurement of the top quark mass in the dileptonic t(t)over-bar decay channel using the mass observables M-bl, M-T2, and M-blv in pp collisions at root=8 TeV

Abstract: SEIDI, CPAN, PCTI and FEDER (Spain). Individuals have received support from the Marie-Curie program and the European Research Council and EPLANET (European Union); the Programa Clarin-COFUND del Principado de Asturias (...)

arXiv : Measurement of b hadron lifetimes in pp collisions at $\sqrt{s} =$ 8 TeV

Abstract: Measurements are presented of the lifetimes of the $${\\mathrm {B}^0}$$B0, $$\\mathrm {B}^0_\\mathrm {s}$$Bs0, $$\\mathrm {\\Lambda }_\\mathrm {b} ^0$$Λb0, and $$\\mathrm {B}_\\mathrm {c}^+$$Bc+ hadrons using the decay channels $${\\mathrm {B}^0}\\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {K^{*}(892)}{}^{0}$$B0→J/ψK∗(892)0, $${\\mathrm {B}^0}\\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {K^0_S}$$B0→J/ψKS0, $$\\mathrm {B}^0_\\mathrm {s} \\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {\\pi ^+}\\mathrm {\\pi ^-}$$Bs0→J/ψπ+π-, $$\\mathrm {B}^0_\\mathrm {s} \\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {\\phi (1020)}$$Bs0→J/ψϕ(1020), $$\\varLambda _\\mathrm {b}^0\\!\\rightarrow \\!\\mathrm {J}/\\psi \\mathrm {\\Lambda }^{0}$$Λb0→J/ψΛ0, and $$\\mathrm {B}_\\mathrm {c}^+ \\!\\rightarrow \\!\\mathrm {J}/\\psi \\mathrm {\\pi ^+}$$Bc+→J/ψπ+. The data sample, corresponding to an integrated luminosity of 19.7$$\\,\\text {fb}^\\text {-1}$$fb-1, was collected by the CMS detector at the LHC in proton–proton collisions at $$\\sqrt{s}=8\\,\\text {Te}\\text {V} $$s=8TeV. The $${\\mathrm {B}^0}$$B0 lifetime is measured to be $$453.0 \\pm 1.6\\,\\text {(stat)} \\pm 1.8\\,\\text {(syst)} \\,\\upmu \\text {m} $$453.0±1.6(stat)±1.8(syst)μm in $$\\mathrm {J}/\\psi \\mathrm {K^{*}(892)}{}^{0}$$J/ψK∗(892)0and $$457.8 \\pm 2.7\\,\\text {(stat)} \\pm 2.8\\,\\text {(syst)} \\,\\upmu \\text {m} $$457.8±2.7(stat)±2.8(syst)μm in $$ \\mathrm {J}/\\psi \\mathrm {K^0_S}$$J/ψKS0, which results in a combined measurement of $$c\\tau _{{\\mathrm {B}^0}} = 454.1 \\pm 1.4\\,\\text {(stat)} \\pm 1.7\\,\\text {(syst)} \\,\\upmu \\text {m} $$cτB0=454.1±1.4(stat)±1.7(syst)μm. The effective lifetime of the $$\\mathrm {B}^0_\\mathrm {s}$$Bs0 meson is measured in two decay modes, with contributions from different amounts of the heavy and light eigenstates. This results in two different measured lifetimes: $$c\\tau _{\\mathrm {B}^0_\\mathrm {s} \\rightarrow \\mathrm {J}/\\psi \\mathrm {\\pi ^+}\\mathrm {\\pi ^-}} = 502.7 \\pm 10.2\\,\\text {(stat)} \\pm 3.4\\,\\text {(syst)} \\,\\upmu \\text {m} $$cτBs0→J/ψπ+π-=502.7±10.2(stat)±3.4(syst)μm and $$c\\tau _{\\mathrm {B}^0_\\mathrm {s} \\rightarrow \\mathrm {J}/\\psi \\mathrm {\\phi (1020)}} = 443.9 \\pm 2.0\\,\\text {(stat)} \\pm 1.5\\,\\text {(syst)} \\,\\upmu \\text {m} $$cτBs0→J/ψϕ(1020)=443.9±2.0(stat)±1.5(syst)μm. The $$\\mathrm {\\Lambda }_\\mathrm {b} ^0$$Λb0 lifetime is found to be $$442.9 \\pm 8.2\\,\\text {(stat)} \\pm 2.8\\,\\text {(syst)} \\,\\upmu \\text {m} $$442.9±8.2(stat)±2.8(syst)μm. The precision from each of these channels is as good as or better than previous measurements. The $$\\mathrm {B}_\\mathrm {c}^+$$Bc+ lifetime, measured with respect to the $${\\mathrm {B}^{+}}$$B+ to reduce the systematic uncertainty, is $$162.3 \\pm 7.8\\,\\text {(stat)} \\pm 4.2\\,\\text {(syst)} \\pm 0.1\\,(\\tau _{{\\mathrm {B}^{+}}})\\,\\upmu \\text {m} $$162.3±7.8(stat)±4.2(syst)±0.1(τB+)μm. All results are in agreement with current world-average values.

Challenges to the chiral magnetic wave using charge-dependent azimuthal anisotropies in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV : arXiv

Abstract: Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

Exclusive and semi-exclusive pi+pi- production in proton-proton collisions at sqrt(s) = 7 TeV

Abstract: A measurement is presented of the exclusive and semi-exclusive production of charged pion pairs in proton-proton collisions, pp to p(p*) + pi+pi- + p(p*) here the pi+pi- pair is emitted at central rapidities, and the scattered protons stay intact (p) or diffractively dissociate (p*) without detection. The measurement is performed with the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity of 450 inverse microbarns collected at a center-of-mass energy of 7 TeV. The dipion cross section, measured for single-pion transverse momentum pt >0.2 GeV and rapidity abs(y)<2, is 26.5 +/- 0.3 (stat) +/- 5.0 (syst) +/- 1.1 (lumi) microbarns. The differential cross sections measured as a function of the invariant mass, pt, and y of the pion pair, and as a function of single-pion pt, are compared to phenomenological predictions.

Search for Supersymmetry in pp Collisions at root s=13 TeV in the Single-Lepton Final State Using the Sum of Masses of Large-Radius Jets

Abstract: Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single lepton, multiple jets, including at least one b-tagged jet, and large missing transverse momentum. The search uses a sample of proton-proton collision data at root s = 13 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1). The observed event yields in the signal regions are consistent with those expected from standard model backgrounds. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production, with gluino decay into either on- or off-mass-shell top squarks. Assuming that the top squarks decay into a top quark plus a stable, weakly interacting neutralino, scenarios with gluino masses up to about 1.9 TeV are excluded at 95% confidence level for neutralino masses up to about 1 TeV.

Measurement of B+/- meson differential production cross sections in pp and PbPb collisions at sqrt(s[NN]) = 5.02 TeV

Abstract: The differential production cross sections of B± mesons are measured via the exclusive decay channels B± → J/ψ K± → μ+μ−K± as a function of transverse momentum in pp and PbPb collisions at a center-of-mass energy √ s NN = 5.02 TeV per nucleon pair with the CMS detector at the LHC. The pp (PbPb) dataset used for this analysis corresponds to an integrated luminosity of 28.0 pb−1 (351 μb−1). The measurement is performed in the B± meson transverse momentum range of 7 to 50 GeV/c, in the rapidity interval |y| < 2.4. In this kinematic range, a strong suppression of the production cross section by about a factor of two is observed in the PbPb system in comparison to the expectation from pp reference data. These results are compared to theoretical calculations incorporating beauty quark diffusion and energy loss in a quark-gluon plasma. Submitted to Physical Review Letters c © 2017 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license ∗See Appendix A for the list of collaboration members ar X iv :1 7 0 5 .0 4 7 2 7 v 1 [h ep -e x ] 1 2 M ay 2 0 1 7