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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
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DOE OSTI2016

Studying the P c ( 4450 ) resonance in J / ψ photoproduction off protons

In this study, a resonance-like structure, the P c (4450), has recently been observed in the J/ψ p spectrum by the LHCb collaboration. We discuss the feasibility of detecting this structure in J/ψ photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P c (4450) to J/ψ p. Our estimates, which take into account the experimental resolution effects, lead to a sizable cross section close to the J/ψ production threshold, which makes future experiments covering this region very promising.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Amplitude analysis of B - → D + π - π - decays

The Dalitz plot analysis technique is used to study the resonant substructures of B - → D + π - π - decays in a data sample corresponding to 3.0 fb -1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D + π - mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D + π - S wave together with virtual contributions from the D*(2007) 0 and B* 0 states, and components corresponding to the D$*\atop{2}$(2460) 0 , D$*\atop{1}$(2680) 0 , D$*\atop{3}$(2760) 0 and D$*\atop{2}$(3000) 0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B- → D + π - π - decays. The D + π - S wave has phase motion consistent with that expected due to the presence of the D$*\atop{0}$(2400) 0 state. These results constitute the first observations of the D$*\atop{3}$(2760) 0 and D$*\atop{2}$(3000) 0 resonances, with significances of 10σ and 6.6σ, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

$L_\mu - L_\tau$ theory of Higgs flavor violation and $(g-2)_\mu$

Several experiments reported hints for the violation of lepton flavor or lepton flavor universality in processes involving muons. Most prominently, there is the hint for a nonzero rate of the flavor violating Higgs decay h→τμ at the LHC, as well as the hint for lepton flavor universality violation in rare B meson decays at the LHCb. In addition, also the long-standing discrepancy in the anomalous magnetic moment of the muon motivates new physics connected to muons. A symmetry which violates lepton flavor universality is Lμ-Lτ: the difference of muon number and tau number. We show that adding vectorlike fermions to a Lμ-Lτ theory generates naturally an effect in the anomalous magnetic moment of the muon and h→τμ, while effects in other τ→μ transitions are systematically suppressed by symmetry arguments. We find that if Lμ-Lτ is gauged it is possible to also accommodate the discrepant b→sμμ data while predicting a τ→3μ and a modified h→μμ rate within reach of upcoming experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Amplitude analysis of B + → J / ψ Φ K + decays

The first full amplitude analysis of B + →J/ψΦK + with J/ψ→μ + μ – , Φ→K + K – decays is performed with a data sample of 3 fb –1 of pp collision data collected at √s = 7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ΦK + , and four J/ψΦ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the K*(1680) + →ΦK + transition.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the decay B s 0 → Φ π + π – and evidence for B 0 → Φ π + π –

The first observation of the rare decay B 0 s →Φπ + π – and evidence for B 0 →Φπ + π – are reported, using pp collision data recorded by the LHCb detector at center-of-mass energies √s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . The branching fractions in the π + π – invariant mass range 400 < m(π + π – ) < 1600 MeV/c 2 are [3.48±0.23±0.17±0.35]×10 –6 and [1.82±0.25±0.41±0.14]×10 –7 for B 0 s →Φπ + π – and B 0 →Φπ + π – respectively, where the uncertainties are statistical, systematic and from the normalization mode B 0 s →ΦΦ. A combined analysis of the π + π – mass spectrum and the decay angles of the final-state particles identifies the exclusive decays B 0 s →Φf 0 (980), B 0 s →Φf 2 (1270), and B 0 s →Φρ 0 with branching fractions of [1.12±0.16+0.09–0.08±0.11]×10 –6 , [0.61±0.13+0.12–0.05±0.06]×10 –6 and [2.7±0.7±0.2±0.2]×10 –7 , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the B ± production asymmetry and the C P asymmetry in B ± → J / ψ K ± decays

The B ± meson production asymmetry in pp collisions is measured using B + →¯D 0 π + decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at center-of-mass energies of √s = 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range 2 < p T < 30 GeV/c, and rapidities in the range 2.1 < y < 4.5 are measured to be A prod (B + ,√s = 7 TeV)=(–0.41±0.49±0.10)×10 –2 , A prod (B + ,√s = 8 TeV)=(–0.53±0.31±0.10)×10 –2 , where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of B + →J/ψK + decays, thus allowing a measurement of the CP asymmetry, A CP (B + →J/ψK + )=(0.09±0.27±0.07)×10 –2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for long-lived scalar particles in B + → K + χ ( μ + μ – ) decays

A search for a long-lived scalar particle χ is performed, looking for the decay B + →K + χ with χ→μ + μ – in pp collision data corresponding to an integrated luminosity of 3 fb –1 , collected by the LHCb experiment at center-of-mass energies of √s = 7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250 < m(χ) < 4700 MeV/c 2 and lifetime 0.1 < τ(χ) < 1000 ps. Upper limits on the branching fraction B(B + →K + χ(μ + μ – )) at 95% confidence level are set as a function of m(χ) and τ(χ), varying between 2 × 10 –10 and 10 –7 . These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the B + → D * – K + π + decay

The B + →D* – K + π + decay potentially provides an excellent way to investigate charm meson spectroscopy. The decay is searched for in a sample of proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . A clear signal is observed, and the ratio of its branching fraction to that of the B + →D* – π + π + normalization channel is measured to be B(B + →D* – K + π + )/B(B + →D* – π + π + )=(6.39±0.27±0.48)×10 –2 , where the first uncertainty is statistical and the second is systematic. This is the first observation of the B + →D* – K + π + decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of branching fraction and direct C P asymmetry in charmless B + → K + K - π + decays at Belle

We introduce a study of the charmless hadronic decay of the charged B meson to the three-body final state K + K - π + . The results are based on a data sample that contains 772 × 1 0 6 B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. The measured inclusive branching fraction and direct C P asymmetry are ( 5.38 ± 0.40 ± 0.35 ) × 10 - 6 and - 0.170 ± 0.073 ± 0.017 , respectively, where the first uncertainties are statistical and the second are systematic. The K + K - invariant mass distribution of the signal candidates shows an excess in the region below 1.5 GeV / c 2 , which is steady with the previous studies from BABAR and LHCb. In addition, strong evidence of a large direct C P asymmetry is found in the low K + K - invariant-mass region.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of charmless baryonic decays B ( s ) 0 → p p ¯ h + h ' –

Decays of B 0 and B 0 s mesons to the charmless baryonic final states p¯ph + h' – , where h and h' each denote a kaon or a pion, are searched for using the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . Four-body charmless baryonic B 0 s decays are observed for the first time. The decays B 0 s →p¯pK + K – , B 0 s →p¯pK ± π ∓ , B 0 →p¯pK ± π ∓ and B 0 →p¯pπ + π – are observed with a significance greater than 5 standard deviations; evidence at 4.1 standard deviations is found for the B 0 →p¯pK + K – decay and an upper limit is set on the branching fraction for B 0 s →p¯pπ + π – . Branching fractions in the kinematic region m(p¯p) < 2850 MeV/c 2 are measured relative to the B 0 →J/ψ(→p¯p)K*(892) 0 channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the shape of the Λ b 0 → Λ c + μ – ν ¯ μ differential decay rate

A measurement of the shape of the differential decay rate and the associated Isgur-Wise function for the decay Λ 0 b →Λ + c μ – ¯νμ is reported, using data corresponding to 3 fb –1 collected with the LHCb detector in proton-proton collisions. The Λ + c μ – ¯ν μ (+anything) final states are reconstructed through the detection of a muon and a Λ + c baryon decaying into pK – π + , and the decays Λ 0 b →Λ + c π + π – μ – ¯ν μ are used to determine contributions from Λ 0 b →Λ* c + μ – ¯νμ decays. The measured dependence of the differential decay rate upon the squared four-momentum transfer between the heavy baryons, q 2 , is compared with expectations from heavy-quark effective theory and from unquenched lattice QCD predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Updated determination of D 0 – D ¯ 0 mixing and C P violation parameters with D 0 → K + π – decays

We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D 0 →K + π – to D 0 →K – π + rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb –1 recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity ( CP ) symmetry, the mixing parameters are determined to be x' 2 =(3.9±2.7)×10 –5 , y'=(5.28±0.52)×10 –3 , and R D =(3.454±0.031)×10 –3 . Without this assumption, the measurement is performed separately for D 0 and D¯ 0 mesons, yielding a direct CP-violating asymmetry A D =(–0.1±9.1)×10 –3 , and magnitude of the ratio of mixing parameters 1.00 < |q/p| < 1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for weakly decaying b -flavored pentaquarks

Investigations of the existence of pentaquark states containing a single b (anti)quark decaying weakly into four specific final states J/ψK + π – p, J/ψK – π – p, J/ψK – π + p, and J/ψΦ(1020)p are reported. The data sample corresponds to an integrated luminosity of 3.0 fb –1 in 7 and 8 TeV pp collisions acquired with the LHCb detector. Signals are not observed and upper limits are set on the product of the production cross section times branching fraction with respect to that of the Λ 0 b .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Test of lepton flavor universality by the measurement of the B 0 → D * – τ + ν τ branching fraction using three-prong τ decays

The ratio of branching fractions R(D* – )≡B(B 0 →D* – τ + ν τ )/B(B 0 →D* – μ + ν μ ) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . The τ lepton is reconstructed with three charged pions in the final state. A novel method is used that exploits the different vertex topologies of signal and backgrounds to isolate samples of semitauonic decays of b hadrons with high purity. Using the B 0 →D*π + π – π + decay as the normalization channel, the ratio B(B 0 →D* – τ + ν τ )/B(B 0 →D* – π + π – π + ) is measured to be 1.97±0.13±0.18, where the first uncertainty is statistical and the second systematic. An average of branching fraction measurements for the normalization channel is used to derive B(B 0 →D* – τ + ν τ )=(1.42±0.094±0.129±0.054)%, where the third uncertainty is due to the limited knowledge of B(B 0 →D* – π + π – π + ). A test of lepton flavor universality is performed using the well-measured branching fraction B(B0→D*–μ+νμ) to compute R(D* – )=0.291±0.019±0.026±0.013, where the third uncertainty originates from the uncertainties on B(B0→D* – π + π – π + ) and B(B 0 →D* – μ + ν μ ). This measurement is in agreement with the Standard Model prediction and with previous measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Bottom-quark fusion processes at the LHC for probing Z ' models and B -meson decay anomalies

We investigate models of a heavy neutral gauge boson Z' coupling mostly to third generation quarks and second generation leptons. In this scenario, bottom quarks arising from gluon splitting can fuse into Z' allowing the LHC to probe it. In the generic framework presented, anomalies in B -meson decays reported by the LHCb experiment imply a flavor-violating b s coupling of the featured Z ' constraining the lowest possible production cross section. A novel approach searching for a Z ' (→ μ μ) in association with at least one bottom-tagged jet can probe regions of model parameter space existing analyses are not sensitive to.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Observation of the Decay B c + → B s 0 π +

The result of a search for the decay B c + → B s 0 π + is presented, using the B s 0 → D s - π + and B s 0 → J /&psi;&phi; channels. The analysis is based on a data sample of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1 fb -1 taken at a center-of-mass energy of 7 TeV, and 2 fb -1 taken at 8 TeV. The decay B c + → B s 0 π + is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is [σ (B c + )/σ (B s 0 )] × B ( B c + → B s 0 π + ) =[2.37±0.31 (stat) ± 0.11 (syst)$ +0.17\atop{-0.13} $(τ$_B{_c^+}$)]×10 -3 , in the pseudorapidity range 2<η(B)<5, where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the $B{_c^+}$ lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for Hidden-Sector Bosons in B 0 → K * 0 μ + μ – Decays

A search is presented for hidden-sector bosons, χ, produced in the decay B 0 →K*(892) 0 χ, with K*(892) 0 →K + π - and χ→μ + μ - . The search is performed using pp-collision data corresponding to 3.0fb -1 collected with the LHCb detector. No significant signal is observed in the accessible mass range 214 ≤m (χ) ≤ 4350 MeV, and upper limits are placed on the branching fraction product $\mathscr{B}$(B 0 →K*(892) 0 χ) × $\mathscr{B}$(χ→μ + μ - ) as a function of the mass and lifetime of the χ boson. These limits are of the order of 10 -9 for χ lifetimes less than 100 ps over most of the m(χ) range, and place the most stringent constraints to date on many theories that predict the existence of additional low-mass bosons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗