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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Simultaneous determination of CKM angle γ and charm mixing parameters

A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D 0 and $ \overline{D} $ 0 mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $ x=\left({0.400}_{-0.053}^{+0.052}\right)\% $ and y = $ \left({0.630}_{-0.030}^{+0.033}\right)\% $. The angle γ is found to be γ = ($ 65.4_{-4.2}^{+3.8} $)° and is the most precise determination from a single experiment.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Measurement of the effective leptonic weak mixing angle

Using pp collision data at $\sqrt{s}$ = 13 TeV, recorded by the LHCb experiment between 2016 and 2018 and corresponding to an integrated luminosity of 5.4 fb −1 , the forward-backward asymmetry in the pp → Z/γ* → μ + μ − process is measured. The measurement is carried out in ten intervals of the difference between the muon pseudorapidities, within a fiducial region covering dimuon masses between 66 and 116 GeV, muon pseudorapidities between 2.0 and 4.5 and muon transverse momenta above 20 GeV. These forward-backward asymmetries are compared with predictions, at next-to-leading order in the strong and electroweak couplings. The measured effective leptonic weak mixing angle is ${\sin}^2{\theta}_{\textrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023,$ where the first uncertainty is statistical, the second arises from systematic uncertainties associated with the asymmetry measurement, and the third arises from uncertainties in the fit model used to extract ${\sin}^2{\theta}_{\textrm{eff}}^{\ell }$ from the asymmetry measurement. This result is based on an arithmetic average of results using the CT18, MSHT20, and NNPDF31 parameterisations of the proton internal structure, and is consistent with previous measurements and with predictions from the global electroweak fit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Production of Charmonium at Threshold in Hall A and C at Jefferson Lab

Here, we describe in this paper two approved experiments in Hall A and Hall C at Jefferson Lab that will investigate the pure gluonic component of the strong interaction of Quantum ChromoDynamics by measuring the elastic J/ψ electro and photo-production cross section in the threshold region as well as explore the nature of the recently discovered LHCb charmed pentaquarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Studying the $P_c(4450)$ Resonance in $J/\psi $ Photoproduction Off Protons

Here, the LHCb has reported the observation of a resonancelike structure, the $P_c(4450)$, in the $J/\psi $ p invariant masses. In our work, we discuss the feasibility of detecting this structure in $J/\psi $ photoproduction, e.g. in the measurements that have been approved for the experiments in Hall A/C and in Hall B with CLAS12 at JLab. Also the GlueX Collaboration has already reported preliminary results. We take into account the experimental resolution effects, and perform a global fit to world J/psi photoproduction data in order to study the possibility of observing the $P_c(4450)$ signal in future JLab data. We present a first estimate of the upper limit for the branching ratio of the $P_c(4450)$ into the $J/\psi $ p channel, and we study the angular distributions of the differential cross sections. This will shed light on the nature and couplings of the $P_c(4450)$ structure in the future photoproduction experiments.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Search for the doubly charmed baryon $\Xi_{cc}^+$

A search for the doubly charmed baryon $\Xi_{cc}^+$ is performed through its decay to the $Λ$ $^{+}_{c}$ K – π + final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb –1 . No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c 2 . Upper limits are set at 95% credibility level on the ratio of the $\Xi_{cc}^+$ production cross-section times the branching fraction to that of $Λ$ $^{+}_{c}$ and $\Xi_{cc}^{++}$ baryons. The limits are determined as functions of the $\Xi_{cc}^+$ mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

J/ψ photoproduction at the threshold with GlueX

High-statistics total cross sections for the vector meson photoproduction at the threshold: γp → ωp (from A2 at MAMI, ELPH, and CBELSA), γp → ϕp (from CLAS6 at JLab and LEPS at SPring-8), and γp → J/ψp (from GlueX at JLab) allow one to extract the absolute value of vector meson nucleon scattering length using Vector Meson Dominance (VMD) model. The “young” vector meson hypothesis may explain the fact that the obtained scattering length values for the nucleon. ϕ-meson compared to the typical hadron size of approximately ∼ 1 fm indicates that the proton is more transparent for the ϕ-meson compared to the ω-meson and is much less transparent than the J/ψ-meson. The extended analysis of Υ-meson photoproduction using quasi-data from the QCD approach is in perfect agreement with the light-meson findings using experimental data. Finally, the ability of J-PARC to measure $π^{–}p → ϕn$ and $π^{–}p → J/ψn$ at the threshold, which are free from the VMD model, is presented. It enables one to understand the dynamics of $s\bar{s}$ and $c\bar{c}$ production at threshold and to search for the effects of LHCb’s heavy quark exotic states.

Vector meson nucleon scattering length↗
DOE OSTI2018

Timing layers, 4- and 5-dimension tracking

The combination of precision space and time information in particle tracking, the so called 4D tracking, is being considered in the upgrade of the ATLAS, CMS and LHCb experiments at the High-Luminosity LHC, set to start data taking in 2024–2025. Regardless of the type of solution chosen, space–time tracking brings benefits to the performance of the detectors by reducing the background and sharpening the resolution; it improves tracking performances and simplifies tracks combinatorics. Space–time tracking also allows investigating new physics channels, for example it opens up the possibilities of new searches in long-living particles by measuring accurately the time of flight between the production and the decay vertexes. The foreseen applications of 4D tracking in experiments with very high acquisition rates, for example at HL-LHC, add one more dimension to the problem, increasing dramatically the complexity of the read-out system and that of the whole detector design: we call 5D tracking the application of 4D tracking in high rate environments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Cold nuclear matter effects on J/ψ and Y production in p + Pb collisions at 5 TeV and Pb + Pb collisions at 5.1 TeV

We make a systematic study of the modifications of and production in p+Pb collisions at $\sqrt{s}$$_ {NN}$ = 5 TeV at the LHC. Here, we compare the uncertainties in the EPS09 shadowing parameterization to the calculated mass and scale uncertainties obtained employing the EPS09 NLO central set. We study the dependence of the results on the proton parton density and the choice of the nuclear modifications. We check whether the results obtained are consistent at leading and next-to-leading order. The calculations are compared to the available ALICE and LHCb data on the nuclear modification factors, R pA (y) and R pA (p T ) , as well as the forward-backward asymmetries, R FB (y) and R FB (p T ) . Finally, we make predictions for the next Pb+Pb run at $\sqrt{s}$$_ {NN}$ = 5.1 TeV in Run 2 of the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

A fixed-target programme at the LHC for heavy-ion, hadron, spin and astroparticle physics: AFTER@LHC

Thanks to its multi-TeV LHC proton and lead beams, the LHC complex allows one to perform the most energetic fixed-target experiments ever and to study with high precision pp, pd and pA collisions at √ s NN = 115 GeV and Pbp and PbA collisions at √ s NN = 72 GeV. In conclusion we present a selection of feasibility studies for the production of quarkonia, open heavy-flavor mesons as well as light-flavor hadrons in pA and PbA collisions using the LHCb and ALICE detectors in a fixed-target mode.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Search for the lepton-flavour violating decay D 0 → e ± μ ∓

A search for the lepton-flavour violating decay D 0 →e ± μ ∓ is made with a dataset corresponding to an integrated luminosity of 3.0 fb -1 of proton–proton collisions at centre-of-mass energies of 7 TeV and 8 TeV, collected by the LHCb experiment. Candidate D 0 mesons are selected using the decay D *+ → D 0 π + and the D 0 →e ± μ ∓ branching fraction is measured using the decay mode D 0 → K - π + as a normalization channel. No significant excess of D 0 →e ± μ ∓ candidates over the expected background is seen, and a limit is set on the branching fraction, B(D 0 →e ± μ ∓ ) < 1.3 × 10 -8 , at 90% confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

First observation of the decay D 0 → K – π + μ + μ – in the ρ 0 – ω region of the dimuon mass spectrum

A study of the decayD 0 → K – π + μ + μ – is performed using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2.0 fb -1 . Decay candidates with muon pairs that have an invariant mass in the range 675-875 MeV/c 2 are considered. This region is dominated by the ρ 0 and ω resonances. The branching fraction in this range is measured to be $\mathscr{B}$(D 0 →K - π + μ + μ - )=(4.17 ± 0.12 (stat) ± 0.40 (syst) )× 10 -6 . This is the first observation of the decay D 0 →K - π + μ + μ - . Its branching fraction is consistent with the value expected in the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for B c + decays to the p p – π + final state

A search for the decays of the B c + meson to p p – π + is performed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb -1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. No signal is found and an upper limit, at 95% confidence level, is set, $\frac{fc}{fu}$ × $\mathscr{B}$ ( B c + → p p – π + ) < 3.6 × 10 -8 in the kinematic region m($p\bar{p}$) < 2.85 GeV/c 2 , p T (B) < 20 GeV/ c and 2.0 < y(B) < 4.5 where $\mathscr{B}$ is the branching fraction and f c (f u ) is the is the fragmentation fraction of the b quark into a B c +(B + ) meson.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Observation of the Λ b 0 → Λ φ decay

The Λ b 0 → Λ φ decay is observed using data corresponding to an integrated luminosity of 3.0 fb -1 recorded by the LHCb experiment. The decay proceeds at leading order via a b→$s\bar{s}s$ loop transition and is therefore sensitive to the possible presence of particles beyond the Standard Model. A first observation is reported with a significance of 5.9 standard deviations. The value of the branching fraction is measured to be (5.18 ± 1.04 ±0.35$^{+0.67}_{-0.62}$)×10 -6 , where the first uncertainty is statistical, the second is systematic, and the third is related to external inputs. Triple-product asymmetries are measured to be consistent with zero.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of CP observables in B ± → DK ± and B ± → Dπ ± with two- and four-body D decays

Measurements of CP observables in B ± → DK ± and B ± → Dπ ± decays are presented where the D meson is reconstructed in the final states K ± π ∓ , π ± K ∓ , K + K – , π + π – , K ± π ∓ π + π – , π ± K ∓ π + π – and π + π – π + π – . This analysis uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb –1 . Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle γ. The analysis of the four-pion D decay mode is the first of its kind.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

First study of the CP-violating phase and decay-width difference in B s 0 → ψ ( 2 S ) φ decays

A time-dependent angular analysis of B s 0 → ψ ( 2 S ) φ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb –1 collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the B$^{0}_{s}$ system are measured to be φ s =0.23$^{+0.29}_{–0.28}$ ± 0.02 rad and ΔΓ s =0.066$^{+0.041}_{–0.044}$ ± 0.007 ps –1 , respectively, where the first uncertainty is statistical and the second systematic. This is the first time that φ s and ΔΓ s have been measured in a decay containing the ψ(2S) resonance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurements of long-range near-side angular correlations in s N N = 5 TeV proton-lead collisions in the forward region

Two-particle angular correlations are studied in proton-lead collisions at a nucleon–nucleon centre-of-mass energy of s N N = 5 TeV , collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, Δη, and relative azimuthal angle, Δφ, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, Δφ≈0, is observed in the pseudorapidity range 2.0 < η < 4.9. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to η=4.9. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the B s 0 → J / ψ η lifetime

Using a data set corresponding to an integrated luminosity of 3 fb –1 , collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the B s 0 → J / ψ η decay mode, τ eff , is measured to be τ eff =1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τ eff corresponds to the lifetime of the light B$^{0}_{s}$ mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for the CP-violating strong decays η → π + π - and η' (958)→ π + π -

A search for the CP-violating strong decays η→π + π - and η'(958)→π + π - has been performed using approximately 2.5×10 7 events of each of the decays D + →π + π + π - and D$+\atop{s}$→π + π + π - , recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb -1 of pp collision data recorded during LHC Run 1 and 0.3 fb -1 recorded in Run 2. No evidence is seen for D$+\atop{s}$→π + η(') with η(')→π + π - , and upper limits at 90% confidence level are set on the branching fractions, B(η→π + π - )<1.6×10 -5 and B(η'→π + π - )<1.8×10 -5 . The limit for the η decay is comparable with the existing one, while that for the η' is a factor of three smaller than the previous limit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗