D. Johnson
A5100729411- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Black Holes and Theoretical Physics
- Atomic and Subatomic Physics Research
- Computational Physics and Python Applications
- Particle Accelerators and Free-Electron Lasers
- Medical Imaging Techniques and Applications
- Distributed and Parallel Computing Systems
- Mathematics, Computing, and Information Processing
- Simulation Techniques and Applications
- Superconducting Materials and Applications
- Crystallization and Solubility Studies
- Nuclear physics research studies
- X-ray Diffraction in Crystallography
- Stochastic processes and statistical mechanics
- Radiation Detection and Scintillator Technologies
- Astrophysics and Cosmic Phenomena
- Advanced NMR Techniques and Applications
- Cosmology and Gravitation Theories
- Ocular Diseases and Behçet’s Syndrome
- Nuclear Physics and Applications
University of Birmingham
2024-2025
Massachusetts Institute of Technology
2022-2024
Northwestern University
2024
University of Tennessee Health Science Center
2024
University of Cincinnati
2013-2023
University of Padua
2023
University of Kansas
1989-2022
European Organization for Nuclear Research
2014-2021
United States Public Health Service Commissioned Officers Association
2021
University of Oxford
2010-2020
The LHCb experiment has been taking data at the Large Hadron Collider (LHC) CERN since end of 2009. One its key detector components is Ring-Imaging Cherenkov (RICH) system. This provides charged particle identification over a wide momentum range, from 2–100 GeV/c. operation and control, software, online monitoring RICH system are described. performance presented, as measured using LHC. Excellent separation hadronic types (π, K, p) achieved.
This paper reports world averages of measurements $b$-hadron, $c$-hadron, and $\tau$-lepton properties obtained by the Heavy Flavor Averaging Group using results available through September 2018. In rare cases, significant several months later are also used. For averaging, common input parameters used in various analyses adjusted (rescaled) to values, known correlations taken into account. The include branching fractions, lifetimes, neutral meson mixing parameters, CP violation semileptonic...
This paper reports world averages of measurements $b$-hadron, $c$-hadron, and $\tau$-lepton properties obtained by the Heavy Flavour Averaging Group using results available before April 2021. In rare cases, significant several months later are also used. For averaging, common input parameters used in various analyses adjusted (rescaled) to values, known correlations taken into account. The include branching fractions, lifetimes, neutral meson mixing parameters, CP violation semileptonic...
We report the first evidence of charmless semileptonic decays B mesons. In momentum interval 2.4–2.6 GeV/c where background from b→clν is negligible, average measured b→ueν and b→uμν partial branching ratios ΔBub(2.4,2.6) =(1.8±0.4±0.3)×10−4. Inclusion data 2.2–2.4 GeV/c, lepton yield dominated by b→clν, gives ΔBub(2.2,2.6) =(3.3±0.8±0.8)×10−4. ‖Vub/Vcb‖ depends on theoretical model b→ulν decay approximately 0.1.Received 8 November 1989DOI:https://doi.org/10.1103/PhysRevLett.64.16©1990...
We have measured ${B}^{0}$B${\ifmmode\bar\else\textasciimacron\fi{}}^{0}$ mixing by observing like-sign dilepton events in \ensuremath{\Upsilon}(4S) decay. Assuming that the semileptonic branching fractions of charged and neutral B mesons are equal decays to ${B}^{+}$${B}^{\mathrm{\ensuremath{-}}}$ 55% time 45% time, we measure parameter r be 0.19\ifmmode\pm\else\textpm\fi{}0.06\ifmmode\pm\else\textpm\fi{}0.06, where first error is statistical second systematic.
The goal of this report is to give a comprehensive overview the rich field forward physics, with special attention topics that can be studied at LHC.The starts presenting selection Monte Carlo simulation tools currently available, chapter 2, then enters phenomenology QCD low, 3, and high, 4, momentum transfer, while unique scattering conditions central exclusive production are analyzed in 5.The last two experimental topics, Cosmic Ray Heavy Ion physics presented 6 7 respectively.Chapter 8...
We study the exclusive semileptonic B meson decays ${\mathit{B}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${\mathit{D}}^{\mathrm{*}0}$${\mathit{l}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{} and B${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$\ensuremath{\rightarrow}${\mathit{D}}^{\mathrm{*}+}$${\mathit{l}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{} using data collected with CLEO II detector at...
We report results on the differential and total cross sections for inclusive production of charmed particles ${D}^{\mathrm{*}+}$, ${D}^{\mathrm{*}0}$, ${D}^{0}$, ${D}^{+}$, ${D}_{s}$, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$ in ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ annihilations at \ensuremath{\surd}s=10.55 GeV. Widely used quark fragmentation models are discussed compared with measured charmed-particle momentum distributions. This comparison, as well that...
Using the CLEO II detector and a sample of 955 000 \ensuremath{\Upsilon}(4S) decays we have confirmed charmless semileptonic B mesons. In momentum interval 2.3--2.6 GeV/c observe an excess 107\ifmmode\pm\else\textpm\fi{}15\ifmmode\pm\else\textpm\fi{}11 leptons, which attribute to b\ensuremath{\rightarrow}ul\ensuremath{\nu}. This result yields model-dependent range values for \ensuremath{\Vert}${\mathit{V}}_{\mathit{u}\mathit{b}}$/${\mathit{V}}_{\mathit{c}\mathit{b}}$\ensuremath{\Vert} that...
We have measured the B0B¯0 mixing probability, χd, using a sample of 965 000 BB¯ pairs from Υ(4S) decays. Counting dilepton events, we find χd=0.157±0.016±0.018−0.021+0.028. Using tagged B0 χd=0.149±0.023±0.019±0.010. The first (second) error is statistical (systematic). third reflects ±15% uncertainty in assumption, made both cases, that charged and neutral B contribute equally to events. also obtain limit on CP impurity Bd0 system, ‖Re(εB0)‖<0.045 at 90% C.L.Received 29 April...
The ratio $R$ of the cross section for ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into hadronic final states to QED muon-pair production is measured be 4.34\ifmmode\pm\else\textpm\fi{}0.45\ifmmode\pm\else\textpm\fi{}0.30 and 4.23\ifmmode\pm\else\textpm\fi{}0.20\ifmmode\pm\else\textpm\fi{}0.21 at c.m. energies 50 52 GeV, respectively. From these values an analysis event shapes we deduce a 95%-confidence-level upper limit rate new heavy charge $+\frac{2}{3}e$ or $\ensuremath{-}\frac{1}{3}e$...
We have used the CLEO-II detector at Cornell Electron Storage Ringe (CESR) to study inclusive production of charmonium mesons in a sample 2.15 million BB¯ events. find branching fractions (1.12±0.04±0.06)% for B→J/ψX, (0.34±0.04±0.03)% B→ψ′X, and (0.40±0.06±0.04)% B→χc1X. also some evidence χc2, set an upper limit fraction decay B→ηcX 0.9% 90% confidence level. Momentum spectra J/ψ, ψ′, χc1 are presented. These measurements compared theoretical calculations.Received 13 December...
We consider the decay of Υ(1S) particles produced at CESR into a photon which is observed by CLEO detector plus are not seen. These could be real fall outside our acceptance, or noninteracting. report results search fo process Υ(1S)→γ+''unseen'' for energies >1 GeV, obtaining limits case where ''unseen'' either single particle particle-antiparticle pair. Our upper represent highest sensitivity measurements such decays to date.Received 11 August...
We report new measurements of semileptonic branching fractions $B$ mesons produced at the $\ensuremath{\Upsilon}(4S)$ resonance determined by fitting inclusive electron and muon momentum spectra to different theoretical models. Using $B(\overline{B}\ensuremath{\rightarrow}X{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}})$ denote average for decay electrons muons, we obtain...
We report new measurements of the branching fractions B(B−→D0l−¯ν), B(¯B0→D+l−¯ν), and B(B−→D*0l−¯ν). Combining these results with our previous measurement B(¯B0→D*+l−¯ν), we find that ratio semileptonic widths for final states a vector meson pseudoscalar is (2.6+1.1+1.0−0.6−0.8) charged- to neutral-B-meson lifetimes (0.89±0.19±0.13)(f00f+−) where (f00f+−) neutral- charged-B-meson production at Υ(4S). From ¯B→Dl−¯ν fraction, calculate |Vcb|=0.040±0.006±0.006, first error statistical second...
The HERSCHEL detector consists of a set scintillating counters, designed to increase the coverage LHCb experiment in high-rapidity regions on either side main spectrometer. new improves capabilities for studies diffractive interactions, most notably Central Exclusive Production. In this paper construction, installation, commissioning, and performance are presented.
We report results on inclusive production of the charmed baryon Λc+ from e+e− annihilations at √s=10.5 GeV. Measurements are presented cross section times branching fraction for continuum as observed in six different decay modes, and a new, improved value mass. The into pK−π+ is measured to be 10.0±1.5±1.5 pb summed over all xp. fractions p¯K0, p¯K0π+π−, Λπ+, Λπ+π−π+, Ξ−K+π+ relative that 0.44±0.07±0.05, 0.43±0.12±0.04, 0.18±0.03±0.03, 0.65±0.11±0.12, 0.15±0.04±0.03, respectively. mass...
Using the CLEO detector at Cornell Electron Storage Ring, we have found evidence for L=1 charmed mesons in e+e− annihilations. We observe a D**0 state mass 2461±3±1 MeV/c2 and width 20−12−10+9+9 decaying to D+π−. also see an enhancement m(D*+π−)−m(D*+) mass-difference spectrum by examining D*+ decay-angle dependence, structure consistent with two states D*+π−. lower-mass state, (2428±3±2) (23−6−4+8+10) MeV/c2, assuming that higher-mass component is from decay D**0(2461)→D*+π−. present...
Using a sample of 484 000 B mesons collected with the CLEO detector at Cornell Electron Storage Ring, we have measured B(B\ifmmode\bar\else\textasciimacron\fi{} $^{0}\mathrm{D}^{\mathrm{*}+}$${\mathrm{l}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\nu}) and found that polarization ${D}^{\mathrm{*}+}$ is small. These results are compared models semileptonic decay.
Using the CLEO detector at Cornell Electron Storage Ring, we observe B-meson decays to A, + and report on improved measurements of inclusive branching fractions momentum spectra other baryons.For decay B~A, +X with -+pK m+, find that product frac- tion B(B~A, +X)B(A, +~pK m. +) =(0.273+0.051+0.039)%.Our measured tions noncharmed baryons are B(B~pX) = ( 8.0+0.5+0.3 )%, B(B -+ AX) 3.8+0.4%0.6)%, B(B~:-X)=(0.27+0.05+0.04)%.From these rates studies baryon-lepton baryon- antibaryon correlations...
Using the CLEO II detector, we have measured branching fractions for $\ensuremath{\Upsilon}(3S)\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}\ensuremath{\Upsilon}(1S)$, $\ensuremath{\Upsilon}(3S)\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}\ensuremath{\Upsilon}(2S)$, and cascade $\ensuremath{\Upsilon}(3S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(2S)+X$,...
We report results from a search for the decays ${\mathit{B}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$, ${\mathit{B}}^{0}$\ensuremath{\rightarrow}${\mathit{K}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$, and ${\mathit{B}}^{0}$\ensuremath{\rightarrow}${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{\ensuremath{-}}}$. find 90% confidence level upper limits on branching fractions,...