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Back, J. J.

Publications and source records attributed to Back, J. J..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Observation of $Λ^0_b$ → $D^+ρπ^-π^-$ and $Λ^0_b$ → $D^{*+}ρπ^-π^-$ decays

The multihadron decays $Λ^0_b$ → $D+ρπ-π-$ and $Λ^0_b$ → $D^*+ρπ-π-$ are observed in data corresponding to an integrated luminosity of 3 fb -1 , collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay $Λ^0_b$ → $Λ^+_cπ^+π^-π^-$ as a normalisation channel, the ratio of branching fractions is measured to be $\frac {\mathcal{B} ( Λ^0_b → D^+ρπ^-π^-)} {\mathcal{B} (Λ^0_b → Λ^0_cπ^+π^-π^-)}$ x $\frac{\mathcal{B} (D^+ → K^-π^+π^+)} {\mathcal{B}(Λ^o_c → ρK^-π^-)}$ = (%.35 ± 0.21 ± 0.16)%, where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the $Λ^0_b$ → $D^{*+}ρπ^-π^-$ and $Λ^0_b$ → $D^+ρπ^-π^-$ decays is found to be $\frac {\mathcal{B} ( Λ^0_b → D^{*+}ρπ^-π^-)} {\mathcal{B} (Λ^0_b → D^+ρπ^-π^-)}$ X ($\mathcal{B} (D^{*+}→ D^+π^0)$ + $\mathcal{B} (D^{*+}→ D^+γ)$) = (61.3 ± 4.3 ± 4.0)%.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Searches for rare ${B}_s^0$ and $B^0$ decays into four muons

Searches for rare ${B}_s^0$ and $B^0$ decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb –1 . Direct decays and decays via light scalar and $J/ψ$ resonances are considered. No evidence for the six decays searched for is found and upper limits at the 95% confidence level on their branching fractions ranging between 1.8 x 10 –10 and 2.6 x 10 –9 are set.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Test of lepton universality in beauty-quark decays

The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Snowmass Neutrino Frontier: DUNE Physics Summary

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino oscillation experiment with a primary physics goal of observing neutrino and antineutrino oscillation patterns to precisely measure the parameters governing long-baseline neutrino oscillation in a single experiment, and to test the three-flavor paradigm. DUNE's design has been developed by a large, international collaboration of scientists and engineers to have unique capability to measure neutrino oscillation as a function of energy in a broadband beam, to resolve degeneracy among oscillation parameters, and to control systematic uncertainty using the exquisite imaging capability of massive LArTPC far detector modules and an argon-based near detector. DUNE's neutrino oscillation measurements will unambiguously resolve the neutrino mass ordering and provide the sensitivity to discover CP violation in neutrinos for a wide range of possible values of $\delta_{CP}$. DUNE is also uniquely sensitive to electron neutrinos from a galactic supernova burst, and to a broad range of physics beyond the Standard Model (BSM), including nucleon decays. DUNE is anticipated to begin collecting physics data with Phase I, an initial experiment configuration consisting of two far detector modules and a minimal suite of near detector components, with a 1.2 MW proton beam. To realize its extensive, world-leading physics potential requires the full scope of DUNE be completed in Phase II. The three Phase II upgrades are all necessary to achieve DUNE's physics goals: (1) addition of far detector modules three and four for a total FD fiducial mass of at least 40 kt, (2) upgrade of the proton beam power from 1.2 MW to 2.4 MW, and (3) replacement of the near detector's temporary muon spectrometer with a magnetized, high-pressure gaseous argon TPC and calorimeter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

A Gaseous Argon-Based Near Detector to Enhance the Physics Capabilities of DUNE

This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Identification of charm jets at LHCb

The identification of charm jets is achieved at LHCb for data collected in 2015–2018 using a method based on the properties of displaced vertices reconstructed and matched with jets. The performance of this method is determined using a dijet calibration dataset recorded by the LHCb detector and selected such that the jets are unbiased in quantities used in the tagging algorithm. The charm-tagging efficiency is reported as a function of the transverse momentum of the jet. The measured efficiencies are compared to those obtained from simulation and found to be in good agreement.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Measurement of prompt charged-particle production in pp collisions at $\sqrt{s}$ = 13 TeV

The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5.4 nb -1 . The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges $p_T$ ∋ [80, 10 000) MeV/c and η ∋ [2.0, 4.8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Measurement of the B s 0 → μ + μ - decay properties and search for the B 0 → μ + μ - and B s 0 → μ + μ - γ decays

An improved measurement of the decay $B^0_S$ → $μ^+μ^-$ and searches for the decays $B^0$ → $μ^+μ^+$ and $B^0_S$ → $μ^+μ^-γ$ are performed at the LHCb experiment using data collected in proton-proton collisions at $\sqrt{s}$ = 7, 8 and 13 TeV. corresponding to integrated luminosities of 1, 2 and 6 fb -1 , respectively. The $B^0_S$ → $μ^+μ^-$ branching fraction and effective lifetime are measured to be $\mathscr{B}$($B^0_S$ → $μ^+μ^-$) = (3.09$^{(+0.46+0.15)}_{(-0.43-0.11)}$) x 10 -9 and $τ(B^0_s →μ^+μ^-)$ = (2.07 ± 0.29 ± 0.03) ps, respectively, where the uncertainties include both statistical and systematic contributions. No significant signal for $B^0$ → $μ^+μ^-$ and $B^0_S$ → $μ^+μ^-γ$ decays is found and the upper limits $\mathscr{B}$($B^0$ → $μ^+μ^-$) < 2.6 x 10 -10 and $B^0_S$ → $μ^+μ^-γ$ < 2.0 x 10 -9 at 95% confidence level are determined, where the latter is limited to the range $m_{μμ}$ > 4.9 GeV/c 2 . Additionally, the ratio between the $B^0$ → $μ^+μ^-$ and $B^0_S$ → $μ^+μ^-$ branching fractions is measured to be $\mathscr{R}_{μ+μ-}$ < 0.095 at 95% confidence level. The results are in agreement with the Standard Model predictions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Analysis of Neutral B -Meson Decays into Two Muons

Branching fraction and effective lifetime measurements of the rare decay B s 0 → μ + μ - and searches for the decays B 0 → μ + μ - and B s 0 → μ + μ - γ are reported using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a luminosity of 9 fb - 1 . The branching fraction B ( B s 0 → μ + μ - ) = ( 3.0 9 - 0.43 - 0.11 + 0.46 + 0.15 ) × 10 - 9 and the effective lifetime τ ( B s 0 → μ + μ - ) = 2.07 ± 0.29 ± 0.03 ps are measured, where the first uncertainty is statistical and the second systematic. No significant signal for B 0 → μ + μ - and B s 0 → μ + μ - γ decays is found and upper limits B ( B 0 → μ + μ - ) < 2.6 × 10 - 10 and B ( B s 0 → μ + μ - γ ) < 2.0 × 10 - 9 at the 95% C.L. are determined, where the latter is limited to the range m μ μ > 4.9 GeV / c 2 . The results are in agreement with the standard model expectations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Measurement of $χ_{c1}$(3872) production in proton-proton collisions at $\sqrt{s}$ = 8 and 13 TeV

The production cross-section of the $χ_{c1}$(3872) state relative to the $ψ(2S)$ meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $\sqrt{s}$ = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb -1 , respectively. The two mesons are reconstructed in the $J/ψπ^+π^-$ final state. The ratios of the prompt and nonprompt $χ_{c1}$(3872) to $ψ(2S)$ production cross-sections are measured as a function of transverse momentum, $ρ_T$, and rapidity, y, of the $χ_{c1}$(3872) and $ψ(2S)$ states, in the kinematic range 4 < $ρ_T$ < 20 GeV/c and 2.0< y < 4.5. The prompt ratio is found to increase with $ρ_T$, independently of y. For the prompt component, the double ratio of the $χ_{c1}$(3872) and $ψ(2S)$ production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of $ρ_T$ and centre-of-mass energy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Search for the radiative $Ξ_b^{-}$ → $Ξ^-γ$ decay

The first search for the rare radiative decay $Ξ_b^{-}$ → $Ξ^-γ$ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb -1 . $Ξ_b^{-}$ → $Ξ^-J/ψ$ channel is used as normalization. No $Ξ_b^{-}$ → $Ξ^-γ$ signal is found and an upper limit of $\mathcal{B}$( $Ξ_b^{-}$ → $Ξ^-γ$) < 1.3 x 10 -4 at 95% confidence level is obtained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Study of $\mathrm{B}_{c}^{+}$ decays to charmonia and three light hadrons

Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb -1 collected with the LHCb detector, seven decay modes of the $B^+_c$ meson into a $J/ψ$ or $ψ(2S)$ meson and three charged hadrons, kaons or pions, are studied. The decays $B^+_c$ → $(ψ(2S)$ →J/$ψπ^+π^-$)$π^+$, $B^+_c$→$ψ(2S)π^+π^-π^+, B^+_c$→ J/$ψK^+π^-π^+$ and $B^+_c$ → J/$ψK^+K^-K^+$ are observed for the first time, and evidence for the $B^+_c$ →$ψ(2S)K^+K^-π^+$, decay is found, where J/ψ and $(ψ(2S)$ mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different $B^+_c$ decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Measurement of the W boson mass

The W boson mass is measured using proton-proton collision data at $\sqrt{s}$ = 13 TeV corresponding to an integrated luminosity of 1.7 fb -1 recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon $q/ρ_T$ distribution of a sample of W →$μv$ decays and the $\phi^*$ distribution of a sample of Z → $μμ$ decays the W boson mass is determined to be $m_w$ =80354±23 stat ±10 exp ±17 theory ±9 PDF MeV, where uncertainties correspond to contributions from statistical, experimental systematic, theoretical and parton distribution function sources. This is an average of results based on three recent global parton distribution function sets. The measurement agrees well with the prediction of the global electroweak fit and with previous measurements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Precise determination of the $B^0_S - \bar {B}^0_S$ oscillation frequency

Mesons comprising a beauty quark and strange quark can oscillate between particle ($B^0_s$) and antiparticle ($\bar{B}^0_s$) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δm s . Here we present a measurement of Δm s using $B^0_s$ → $D^–_sπ^+$ decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δm s = 17.7683 ± 0.0051 ± 0.0032 ps –1 , where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δm s precision by a factor of two. We combine this result with previous LHCb measurements to determine Δm s = 17.7656 ± 0.0057 ps –1 , which is the legacy measurement of the original LHCb detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗