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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Search for decays of neutral beauty mesons into four muons

A search for the non-resonant decays B s 0 → μ + μ – μ + μ – and B 0 → μ + μ – μ + μ – is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of 1 and 2 fb –1 collected at centre-of-mass energies of 7 and 8 TeV, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at 95% confidence level are determined to be $\mathcal{B}$ (B$^{0}_{s}$→μ + μ – μ + μ – )< 2.5 × 10 –9 , (B 0 →μ + μ – μ + μ – )< 6.9 × 10 –10 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

SU(5) unification with TeV-scale leptoquarks

It has previously been noted that SU(5) unification can be achieved via the simple addition of light scalar leptoquarks from two split 10 multiplets. We explore the parameter space of this model in detail and find that unification requires at least one leptoquark to have mass below ≈ 16 TeV. We point out that introducing splitting of the 24 allows the unification scale to be raised beyond 10 16 GeV, while a U(1) PQ symmetry can be imposed to forbid dangerous proton decay mediated by the light leptoquarks. The latest bounds from LHC searches are combined and we find that a leptoquark as light as 400 GeV is still permitted. Finally, we discuss the interesting possibility that the leptoquarks required for unification could also be responsible for the 2.6σ deviation observed in the ratio R K at LHCb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Measurements of the branching fractions of Λ c + → pπ – π + , Λ c + → pK – K + , and Λ c + → pπ – K +

The ratios of the branching fractions of the decays Λ c + → pπ – π + , Λ c + → pK – K + , and Λ c + → pπ – K + with respect to the Cabibbo-favoured Λ c + → pK – π + decay are measured using proton-proton collision data collected with the LHCb experiment at a 7 TeV centre-of-mass energy and corresponding to an integrated luminosity of 1.0 fb –1 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for the lepton-flavour violating decays B (s) o → e ± μ ∓

A search for the lepton-flavour violating decays B (s) o → e ± μ ∓ and B o → e ± μ ∓ is performed based on a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb –1 , collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the B ( s) o → e ± μ ∓ decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

First measurement of the CP -violating phase $ {\phi}_s^{d\overline{d}} $ in B s o → (K + π – )(K – π + ) decays

A flavour-tagged decay-time-dependent amplitude analysis of B s o → (K + π – )(K – π + ) decays is presented in the K ± π ∓ mass range from 750 to 1600MeV/c 2 . The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb –1 . Several quasi-two-body decay modes are considered, corresponding to K ± π ∓ combinations with spin 0, 1 and 2, which are dominated by the K o * (800)0 and K o * (1430) o , the K*(892) o and the K 2 * (1430) o resonances, respectively. The longitudinal polarisation fraction for the B 0 s → K*(892)°K¯*(892) 0 decay is measured as f L = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP -violating phase, $ {\phi}_s^{d\overline{d}} $, in b → dd¯s transitions is performed, yielding a value of $ {\phi}_s^{d\overline{d}} $ = –0.10 ± 0.13 (stat) ± 0.14 (syst) rad.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

A measurement of the CP asymmetry difference between Λ c + → pK – K + and pπ – π + decays

The difference between the CP asymmetries in the decays Λ c + → pK – K + and Λ c + → pπ – π + is presented. Proton-proton collision data taken at centre-of-mass energies of 7 and 8 TeV collected by the LHCb detector in 2011 and 2012 are used, corresponding to an integrated luminosity of 3 fb –1 . The Λ c + candidates are reconstructed as part of the Λ b o → Λ c + μ – X decay chain. In order to maximize the cancellation of production and detection asymmetries in the difference, the final-state kinematic distributions of the two samples are aligned by applying phase-space-dependent weights to the Λ c + → pπ – π + sample. This alters the definition of the integrated CP asymmetry to A CP wgt (pπ – π + ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Measurement of the ratio of branching fractions of the decays $Λ_{b}^{o}$ → ψ(2S)Λ and $Λ_{b}^{o}$ → J /ψΛ

Using pp collisions corresponding to 3 fb –1 integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, the ratio of branching fractions B ($Λ_{b}^{o}$ → ψ(2S)Λ)/ B ($Λ_{b}^{o}$ → J /ψΛ) = 0.513 ± 0.023(stat) ± 0.016(syst) ± 0.011 ( B ) is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Observation of the ${B}_s^0 $ → D*±D∓ decay

A search for the B 0 → D *± D ∓ decay is performed using proton-proton collision data at centre-of-mass energies of 7, 8 and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb -1 . The decay is observed with a high significance and its branching fraction relative to the B 0 → D *± D ∓ decay is measured to be $\frac{\mathrm{\mathcal{B}}\left({B}_s^0\to {D}^{\ast \pm }{D}^{\mp}\right)}{\mathrm{\mathcal{B}}\left({B}^0\to {D}^{\ast \pm }{D}^{\mp}\right)}=0.137\pm 0.017\pm 0.002\pm 0.006$, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the $B_{s}^{0}$ and $B^{0}$ hadronisation fractions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
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

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

Prompt and non-prompt J/ψ production cross sections at midrapidity in proton-proton collisions at $ \sqrt{\mathrm{s}} $ = 5.02 and 13 TeV

The production of J /ψ is measured at midrapidity ( |y| < 0 . 9) in proton-proton collisions at \( \sqrt{s} \) = 5 . 02 and 13 TeV, through the dielectron decay channel, using the ALICE detector at the Large Hadron Collider. The data sets used for the analyses correspond to integrated luminosities of \( \mathcal{L} \) int = 19.4 ± 0.4 nb - 1 and \( \mathcal{L} \) int = 32.2 ± 0.5 nb - 1 at \( \sqrt{s} \) = 5 . 02 and 13 TeV, respectively. The fraction of non-prompt J /ψ mesons, i.e. those originating from the decay of beauty hadrons, is measured down to a transverse momentum p T = 2 GeV /c (1 GeV /c ) at \( \sqrt{s} \) = 5 . 02 TeV (13 TeV). The p T and rapidity ( y ) differential cross sections, as well as the corresponding values integrated over p T and y , are carried out separately for prompt and non-prompt J /ψ mesons. The results are compared with measurements from other experiments and theoretical calculations based on quantum chromodynamics (QCD). The shapes of the p T and y distributions of beauty quarks predicted by state-of-the-art perturbative QCD models are used to extrapolate an estimate of the \( \mathrm{b}\overline{\mathrm{b}} \) pair cross section at midrapidity and in the total phase space. The total \( \mathrm{b}\overline{\mathrm{b}} \) cross sections are found to be \( {\sigma}_{\mathrm{b}\overline{\mathrm{b}}} \) = 541 ± 45 (stat . ) ± 69 \( {\left(\mathrm{syst}.\right)}_{-12}^{+10} \) (extr . ) μ b and \( {\sigma}_{\mathrm{b}\overline{\mathrm{b}}} \) = 218 ± 37 (stat . ) ± 31 \( {\left(\mathrm{syst}.\right)}_{-9.1}^{+8.2} \) (extr . ) μ b at \( \sqrt{s} \) = 13 and 5.02 TeV, respectively. The value obtained from the combination of ALICE and LHCb measurements in pp collisions at \( \sqrt{s} \) = 13 TeV is also provided.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Model-independent measurement of mixing parameters in D 0 → K$^{0}_{S}$ π+π– decays

The first model-independent measurement of the charm mixing parameters in the decay D 0 → K$^{0}_{S}$ π+π– is reported, using a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb –1 at a centre-of-mass energy of 7 TeV. The measured values are x = (–0.86 ± 0.53 ± 0.17) x 10 –2 , y = (+0.03 ± 0.46 ± 0.13) x 10 –2 , where the first uncertainties are statistical and include small contributions due to the external input for the strong phase measured by the CLEO collaboration, and the second uncertainties are systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Evidence for the two-body charmless baryonic decay $$ {B}^{+}\to p\overline{\varLambda} $$

A search for the rare two-body charmless baryonic decay B + → p$-\atop{Λ}$ is performed with pp collision data, corresponding to an integrated luminosity of 3 fb -1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. An excess of B + →p$-\atop{Λ}$ candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the B + →K S 0 π + decay for normalisation, B(B + →p$-\atop{Λ}$=2.4$+1.0\atop{0.8}$±0.3 x 10 -7 )where the first uncertainty is statistical and the second systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Study of charmonium and charmonium-like contributions in $\mathrm{B}^+$ → $\mathrm{J/ψηK^+}$ decays

A study of B+ → J/ψηK + decays, followed by J/ψ → μ + μ – and η → γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb –1 The J/ψη mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the B + →(ψ2(3823) → J/ψη)K + and B + → (ψ(4040) → J/ψη)K + decays with significance of 3.4 and 4.7 standard deviations, respectively. This constitutes the first evidence for the ψ 2 (3823) → J/ψη decay.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Dark showers from Z-dark Z′ mixing

Abstract We discuss dark shower signals at the LHC from a dark QCD sector, containing GeV-scale dark pions. The portal with the Standard Model is given by the mixing of theZboson with a darkZ′ coupled to the dark quarks. Both mass and kinetic mixings are included, but the mass mixing is the essential ingredient, as it is the one mediating visible decays of the long-lived dark pions. We focus especially on the possibility that the darkZ′ islighterthan theZ. Indirect constraints are dominated by electroweak precision tests, which we thoroughly discuss, showing that bothZ-pole and low-energy observables are important. We then recast CMS and LHCb searches for displaced dimuon resonances to dark shower signals initiated by the production of on-shellZorZ′, where the visible signature is left by a dark pion decaying toμ + μ − . We demonstrate how dark shower topologies have already tested new parameter space in Run 2, reaching better sensitivity on a light darkZ′ compared to the flavor-changing decays ofBmesons, which can produce a single dark pion at a time, and the electroweak precision tests.

Physics↗
DOE OSTI2025

Tetraquarks in the Born-Oppenheimer approximation

The conventional loosely bound molecule interpretation of the X(3872) is not compatible with the recent LHCb experimental measurement of the ratio of branching fractions $\mathcal{R}$ = Br(X → ψ′γ)/Br(X → ψγ). We systematically determine the entire tetraquark spectrum for J = 0, 1, 2 and refine the calculation of $\mathcal{R}$ in an improved Born-Oppenheimer description of the X(3872) compact tetraquark. This refinement yields a significantly better agreement with experimental data on $\mathcal{R}$ and on the spectroscopy of the states themselves. Extending the diquark-antidiquark paradigm to encompass tetraquarks that are linear super-positions of open charm singlets and color octets, we discover that these exotic resonances manifest as compact shallow bound states of quarks in color force potentials.

Effective Field Theories of QCD↗
DOE OSTI2016

Observations of Λ b 0 →ΛK +π– and Λ b 0 →ΛK + K – decays and searches for other Λ b 0 and Ξb 0 decays to Λh + h' – final states

A search is performed for the charmless three-body decays of the Λ b 0 and Ξ b 0 baryons to the final states Λh+h' – , where h(') = π or K. The analysis is based on a data sample, corresponding to an integrated luminosity of 3 fb –1 of pp collisions, collected by the LHCb experiment. The Λb 0 → ΛK+π– and Λ b 0 → ΛK+K– decays are observed for the first time and their branching fractions and CP asymmetry parameters are measured. Evidence is seen for the Λ b 0 → Λπ+π– decay and limits are set on the branching fractions of Ξ b 0 baryon decays to the Λh+hh' – final states.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗