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Ian Shipsey

University of Oxford, Physics, Faculty Member

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Papers by Ian Shipsey

$Research paper thumbnail of Publisher’s Note: Improved measurement of the branching fraction and energy spectrum of η ′ from Υ ( 1 S ) decays [Phys. Rev. D 74 , 092006 (2006)]$

Publisher’s Note: Improved measurement of the branching fraction and energy spectrum of η ′ from Υ ( 1 S ) decays [Phys. Rev. D 74 , 092006 (2006)]

Physical Review D, 2007

We present an improved measurement of the η ′ meson energy spectrum in Υ(1S) decays, using 1.2 fb... more We present an improved measurement of the η ′ meson energy spectrum in Υ(1S) decays, using 1.2 fb −1 of data taken at the Υ(1S) center-of-mass energy with the CLEO III detector. We compare our results with models of the η ′ gluonic form factor that have been suggested to explain the unexpectedly large B → η ′ X s rate. Models based on perturbative QCD fail to fit the data for large η ′ energies, and thus an explanation outside the realm of the Standard Model or an improved understanding of non-perturbative QCD effects may be needed to account for this large rate.

Precision Determination of theD0Mass

Physical Review Letters, 2007

A precision measurement of the D 0 meson mass has been made using ∼ 281 pb −1 of e + e − annihila... more A precision measurement of the D 0 meson mass has been made using ∼ 281 pb −1 of e + e − annihilation data taken with the CLEO-c detector at the ψ(3770) resonance. The exclusive decay D 0 → K S φ has been used to obtain M (D 0) = 1864.847 ± 0.150(stat) ± 0.095(syst) MeV. This corresponds to M (D 0 D * 0) = 3871.81 ± 0.36 MeV, and leads to a well-constrained determination of the binding energy of the proposed D 0 D * 0 molecule X(3872), as E b = 0.6 ± 0.6 MeV.

Two-photon width of the charmonium stateχc2

Physical Review D, 2006

$Research paper thumbnail of Measurement of absolute hadronic branching fractions of D0 and D+ and σ(e+e− → Dbar D) at Ecm = 3.77 GeV$

Measurement of absolute hadronic branching fractions of D0 and D+ and σ(e+e− → Dbar D) at Ecm = 3.77 GeV

Journal of Physics: Conference Series, 2005

From e + e − collision data acquired with the CLEO detector at CESR, we observe the non-DD decay ... more From e + e − collision data acquired with the CLEO detector at CESR, we observe the non-DD decay ψ(3770) → γχ c1 with a statistical significance of 6.6 standard deviations, using the twophoton cascades to J/ψ and J/ψ → ℓ + ℓ −. We determine σ(e + e − → ψ(3770)) × B(ψ(3770) → γχ c1) = (18.0 ± 3.3 ± 2.5) pb and branching fraction B(ψ(3770) → γχ c1) = (2.8 ± 0.5 ± 0.4) × 10 −3. We set 90% C.L. upper limits for the transition to χ c2 (χ c0) : σ × B < 5.7 pb (< 282 pb) and B < 0.9 × 10 −3 (< 44 × 10 −3). We also determine Γ(ψ(3770) → γχ c1)/Γ(ψ(3770) → π + π − J/ψ) = 1.5 ± 0.3 ± 0.3 (> 1.0 at 90% C.L.), which bears upon the interpretation of X(3872).

$Research paper thumbnail of Publisher’s Note: Improved measurement of the branching fraction and energy spectrum of η ′ from Υ ( 1 S ) decays [Phys. Rev. D 74 , 092006 (2006)]$

Publisher’s Note: Improved measurement of the branching fraction and energy spectrum of η ′ from Υ ( 1 S ) decays [Phys. Rev. D 74 , 092006 (2006)]

by M. Anderson and Ian Shipsey

Physical Review D, 2007

The performance of the CMS muon detector in proton-proton collisions at root s=7 TeV at the LHC

Journal of Instrumentation, 2013

View the article online for updates and enhancements. Related content Calibration of the CMS drif... more View the article online for updates and enhancements. Related content Calibration of the CMS drift tube chambers and measurement of the drift velocity with cosmic rays CMS Collaboration-Performance of the CMS cathode strip chambers with cosmic rays CMS Collaboration-Performance of the CMS drift-tube chamber local trigger with cosmic rays CMS Collaboration-Recent citations Multiboson interactions at the LHC D. R. Green et al

Shape, transverse size, and charged-hadron multiplicity of jets in pp collisions at √s = 7 TeV

Journal of High Energy Physics, 2012

Measurements of jet characteristics from inclusive jet production in protonproton collisions at a... more Measurements of jet characteristics from inclusive jet production in protonproton collisions at a centre-of-mass energy of 7 TeV are presented. The data sample was collected with the CMS detector at the LHC during 2010 and corresponds to an integrated luminosity of 36 pb −1. The mean charged-hadron multiplicity, the differential and integral jet shape distributions, and two independent moments of the shape distributions are measured as functions of the jet transverse momentum for jets reconstructed with the anti-k T algorithm. The measured observables are corrected to the particle level and compared with predictions from various QCD Monte Carlo generators.

Search for the standard model Higgs boson in the H → ZZ → l +l -τ +τ - decay channel in pp collisions at □s = 7 TeV

Journal of High Energy Physics, 2012

A search is reported for the standard model Higgs boson in the H → ZZ → +τ + τ -decay mode, where... more A search is reported for the standard model Higgs boson in the H → ZZ → +τ + τ -decay mode, where = µ or e, in proton-proton collisions at √ s = 7 TeV, corresponding to an integrated luminosity of 4.7 fb -1 collected with the CMS detector at the LHC. No evidence is found for a significant deviation from the background expectation. An upper limit four to twelve times larger than the predicted value is set at 95% confidence level for the product of the standard model Higgs boson production cross section and decay branching fraction in the mass range 190 < m H < 600 GeV.

Search for heavy long-lived charged particles in pp collisions at √s=7 TeV

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012

The result of a search for heavy long-lived charged particles produced in pp collisions at √ s = ... more The result of a search for heavy long-lived charged particles produced in pp collisions at √ s = 7 TeV at the LHC is described. The data sample has been collected using the CMS detector and corresponds to an integrated luminosity of 5.0 fb −1. The inner tracking detectors are used to define a sample of events containing tracks with high momentum and high ionization energy loss. A second sample of events, which have high-momentum tracks satisfying muon identification requirements in addition to meeting high-ionization and long time-of-flight requirements, is analyzed independently. In both cases, the results are consistent with the expected background estimated from data. The results are used to establish cross section limits as a function of mass within the context of models with long-lived gluinos, scalar top quarks and scalar taus. Cross section limits on hyper-meson particles, containing new elementary long-lived hyper-quarks predicted by a vector-like confinement model, are also presented. Lower limits at 95% confidence level on the mass of gluinos (scalar top quarks) are found to be 1098 (737) GeV/c 2. A limit of 928 (626) GeV/c 2 is set for a gluino (scalar top quark) that hadronizes into a neutral bound state before reaching the muon detectors. The lower mass limit for a pair produced scalar tau is found to be 223 GeV/c 2. Mass limits for a hyper-kaon are placed at 484, 602, and 747 GeV/c 2 for hyper-ρ masses of 800, 1200, and 1600 GeV/c 2 , respectively.

Search for B 0 s → μ + μ - And B0 → μ+ μ- Decays

Journal of High Energy Physics, 2012

A search for the rare decays B 0 s → µ + µ -and B 0 → µ + µ -is performed in pp collisions at √ s... more A search for the rare decays B 0 s → µ + µ -and B 0 → µ + µ -is performed in pp collisions at √ s = 7 TeV, with a data sample corresponding to an integrated luminosity of 5 fb -1 collected by the CMS experiment at the LHC. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are B(B 0 s → µ + µ -) < 7.7 × 10 -9 and B(B 0 → µ + µ -) < 1.8 × 10 -9 at 95% confidence level.

Performance of CMS muon reconstruction in pp collision events at √s = 7TeV

Journal of Instrumentation, 2012

The performance of muon reconstruction, identification, and triggering in CMS has been studied us... more The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 pb −1 of data collected in pp collisions at √ s = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum p T larger than a few GeV/c is above 95% over the whole region of pseudorapidity covered by the CMS muon system, |η| < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with p T above a few GeV/c is higher than 90% over the full η range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with p T below 100 GeV/c and, using cosmic rays, it is shown to be better than 10% in the central region up to p T = 1 TeV/c. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.

Measurement of the rapidity and transverse momentum distributions of Z bosons in pp collisions at √(s)=7TeV

Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012

Measurements of the normalized rapidity (y) and transverse momentum (q T) distributions of Drell-... more Measurements of the normalized rapidity (y) and transverse momentum (q T) distributions of Drell-Yan muon and electron pairs in the Z-boson mass region (60 < M < 120 GeV) are reported. The results are obtained using a data sample of protonproton collisions at a center-of-mass energy of 7 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 36 pb −1. The distributions are measured over the ranges |y| < 3.5 and q T < 600 GeV and compared with QCD calculations using recent parton distribution functions. Overall agreement is observed between the models and data for the rapidity distribution, while no single model describes the Z transverse-momentum distribution over the full range.

Study of the production of charged pions, kaons, and protons in pPb collisions at root SNN=5.02 TeV

European Physical Journal C, 2014

Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the... more Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at √ s NN = 5.02 TeV. Charged pions, kaons, and protons in the transverse-momentum range p T ≈ 0.1-1.7 GeV/c and laboratory rapidity |y| < 1 are identified via their energy loss in the silicon tracker. The average p T increases with particle mass and the charged multiplicity of the event. The increase of the average p T with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that EPOS LHC, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike HIJING and AMPT. The p T spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity.

Inclusive search for squarks and gluinos in pp collisions at √s=7TeV

Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012

A search is performed for heavy particle pairs produced in ffiffi ffi s p ¼ 7 TeV proton-proton c... more A search is performed for heavy particle pairs produced in ffiffi ffi s p ¼ 7 TeV proton-proton collisions with 35 pb À1 of data collected by the CMS experiment at the LHC. The search is sensitive to squarks and gluinos of generic supersymmetry models, provided they are kinematically accessible, with minimal assumptions on properties of the lightest superpartner particle. The kinematic consistency of the selected events is tested against the hypothesis of heavy particle pair production using the dimensionless razor variable R, related to the missing transverse energy E miss T. The new physics signal is characterized by a broad peak in the distribution of M R , an event-by-event indicator of the heavy particle mass scale. This new approach is complementary to E miss T-based searches. After background modeling based on data, and background rejection based on R and M R , no significant excess of events is found beyond the standard model expectations. The results are interpreted in the context of the constrained minimal supersymmetric standard model as well as two simplified supersymmetry models.

Studies of jet quenching using isolated-photon plus jet correlations in PbPb and pp collisions at root s(NN)=2.76 TeV

Physics Letters B, 2013

Page 1. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2012-089 2012/05/02 CMS-HIN-... more

Measurement of four-jet production in proton-proton collisions at root s=7 TeV

Physical Review D, 2014

Using the "Rivet" and "Professor" framework, we construct a new PYTHIA 6 tune using the CTEQ6L1 P... more Using the "Rivet" and "Professor" framework, we construct a new PYTHIA 6 tune using the CTEQ6L1 PDF and two new PYTHIA 8 UE tunes (one using CTEQ6L1 and one using the HER-APDF1.5LO). By simultaneously fitting CDF data from collisions at 300 GeV, 900 GeV, and 1.96 TeV together with CMS data for pp collisions at 7 TeV, we test the Underlying Event (UE) models and constrain their parameters, allowing for more precise predictions at 13 TeV and 14 TeV. The consistency of these new tunes with measurements of double-parton scattering (DPS) is also investigated. DPS-based tunes are also extracted, relying on differential cross sections as a function of correlation observables, for the production of exactly four jets in proton-proton collisions. From this measurement it is found that the addition of parton showers to fixed-order matrix element calculations describe the measured differential cross sections in only some regions of phase space and that including a contribution from double parton scattering in the models brings the predictions closer to the data.

The CMS Collaboration

Nuclear Physics A, 2009

Ultra-peripheral heavy ion collisions provide a unique opportunity to study the parton distributi... more Ultra-peripheral heavy ion collisions provide a unique opportunity to study the parton distributions in the colliding nuclei via the measurement of photo-nuclear jet production. An analysis of jet production in ultra-peripheral Pb+Pb collisions at √ s NN = 5.02 TeV performed using data collected with the ATLAS detector in 2015 is described. The data set corresponds to a total Pb+Pb integrated luminosity of 0.38 nb −1. The ultra-peripheral collisions are selected using a combination of forward neutron and rapidity gap requirements. The cross-sections, not unfolded for detector response, are compared to results from Pythia Monte Carlo simulations re-weighted to match a photon spectrum obtained from the STARlight model. Qualitative agreement between data and these simulations is observed over a broad kinematic range suggesting that using these collisions to measure nuclear parton distributions is experimentally realisable.

Time reconstruction and performance of the CMS electromagnetic calorimeter

Journal of Instrumentation, 2010

The resolution and the linearity of time measurements made with the CMS electromagnetic calorimet... more The resolution and the linearity of time measurements made with the CMS electromagnetic calorimeter are studied with samples of data from test beam electrons, cosmic rays, and beam-produced muons. The resulting time resolution measured by lead tungstate crystals is better than 100 ps for energy deposits larger than 10 GeV. Crystalto-crystal synchronization with a precision of 500 ps is performed using muons produced with the first LHC beams in 2008.

Performance study of the CMS barrel resistive plate chambers with cosmic rays

Journal of Instrumentation, 2010

Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL... more

Performance of the CMS drift tube chambers with cosmic rays

Journal of Instrumentation, 2010

Page 1. Performance of the CMS drift tube chambers with cosmic rays This article has been downloa... more