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Buchanan, E.

Publications and source records attributed to Buchanan, E..

At least 37 records · Page 2
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DOE OSTI2018

Search for excited Bc + states

A search is performed in the invariant mass spectrum of the B c + π + π - system for the excited B c + states B c (2 1 S 0 ) + and B c (2 3 S 1 ) + using a data sample of pp collisions collected by the LHCb experiment at the centre-of-mass energy of $\sqrt{s}$=8 TeV, corresponding to an integrated luminosity of 2 fb -1 . No evidence is seen for either state. Upper limits on the ratios of the production cross-sections of the B c (2 1 S 0 ) + and B c (2 3 S 1 ) + states times the branching fractions of Bc(21S0)+ → B c + π + π - and B c (2 3 S 1 ) + → B c * + π + π - over the production cross-section of the Bc+ state are given as a function of their masses. They are found to be between 0.02 and 0.14 at 95% confidence level for Bc(2 1 S 0 ) + and B c (2 3 S 1 ) + in the mass ranges [6830, 6890] MeV/c 2 and [6795, 6890] MeV/c 2 , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Updated search for long-lived particles decaying to jet pairs

A search is presented for long-lived particles with a mass between 25 and 50GeV/c 2 and a lifetime between 2 and 500 ps, using proton–proton collision data corresponding to an integrated luminosity of 2.0fb -1 , collected by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The particles are assumed to be pair-produced in the decay of a 125GeV/c 2 Standard-Model-like Higgs boson. The experimental signature is a single long-lived particle, identified by a displaced vertex with two associated jets. No excess above background is observed and limits are set on the production cross-section as a function of the mass and lifetime of the long-lived particle.

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DOE OSTI2017

Measurement of $CP$ violation in $B^0$ → $J/ψK^S_0$ and $B^0$ → $ψ(2S)K^S_0$ decays

A measurement is presented of decay-time-dependent $CP$ violation in the decays $B^0$ → $J/ψ K^S_0$ and $B^0$ → $ψ(2S)K^S_0$, where the $J/ψ$ is reconstructed from two electrons and the $ψ(2S)$ from two muons. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb -1 . The $CP$-violation observables are measured to be $$ C(B^0 → J/ψ K_S^0) = 0.12± 0.07 ± 0.02, $$ $$ S(B^0 → J/ψ K_S^0) = 0.83 ± 0.08 ± 0.01, $$ $$ C(B^0 → ψ(2S) K_S^0) = -0.05 ± 0.10 ± 0.01, $$ $$ S(B^0 → ψ(2S) K_S^0) = 0.84 ± 0.10 ± 0.01, $$ where $C$ describes $CP$ violation in the direct decay, and $S$ describes $CP$ violation in the interference between the amplitudes for the direct decay and for the decay after $B^0$ - $\bar{B}^0$ oscillation. The first uncertainties are statistical and the second are systematic. The two sets of results are compatible with the previous LHCb measurement using $B^0$ → $J/ψ K^S_0$ decays, where the $J/ψ$ meson was reconstructed from two muons. The averages of all three sets of LHCb results are C ( B 0 &#x2192;<!-- → --> [ c c &#x00AF;<!-- ¯ --> ] K S 0 ) = &#x2212;<!-- - --> 0.017 &#x00B1;<!-- ± --> 0.029 , S ( B 0 &#x2192;<!-- → --> [ c c &#x00AF;<!-- ¯ --> ] K S 0 ) = 0.760 &#x00B1;<!-- ± --> 0.034 , under the assumption that higher-order contributions to the decay amplitudes are negligible. The uncertainties include statistical and systematic contributions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of $CP$ observables in $B^±$ → $DK^{*±}$ decays using two- and four-body $D$ final states

Measurements of $CP$ observables in $B^±$ → $DK^{*±}$ decays are presented, where $D$ denotes a superposition of $D^0$ and $\bar{D}^0$ meson states. Decays of the $D$ meson to $K^-π^+$, $K^-K^+$, $π^-π^+$, $K^-π^+π^-π^+$ and $π^-π^+π^-π^+$ are used and the $K^{*±}$ meson is reconstructed in the $K_S^0π^±$ final state. This analysis uses a data sample of pp collisions collected with the LHCb experiment, corresponding to integrated luminosities of 1 fb -1 , 2 fb -1 and 1.8 fb -1 at centre-of-mass energies $\sqrt{s}$=7 TeV, 8 TeV and 13 TeV, respectively. The sensitivity of the results to the CKM angle $γ$ is discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Improved limit on the branching fraction of the rare decay ${{K} ^0_{\mathrm { \scriptscriptstyle S}}} \rightarrow \mu ^+\mu ^-$

A search for the decay ${{K} ^0_{\mathrm { \scriptscriptstyle S}}} \rightarrow \mu ^+\mu ^-$ is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of 3fb -1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8TeV. The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of Β (${{K} ^0_{\mathrm { \scriptscriptstyle S}}} \rightarrow \mu ^+\mu ^-$ ) < 0.8 (1.0) × 10 -9 at 90%(95%) confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.

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 B 0 , B s 0 , B + and Λ b 0 production asymmetries in 7 and 8 TeV proton–proton collisions

The B 0 , B s 0 , B + and Λ b 0 hadron production asymmetries are measured using a data sample corresponding to an integrated luminosity of 3.0 fb –1 , collected by the LHCb experiment in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV. The measurements are performed as a function of transverse momentum and rapidity of the b hadrons within the LHCb detector acceptance. The overall production asymmetries, integrated over transverse momentum and rapidity, are also determined.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Test of lepton universality with $B^0 → K^{*0} ℓ^+ ℓ^-$ decays

A test of lepton universality, performed by measuring the ratio of the branching fractions of the $B^0 → K^{*0}μ^+μ^-$ and $B^0$ → $K^{*0}e^+e^-$ decays, $R_{K^{*0}}$, is presented. The $K^{*0}$ meson is reconstructed in the final state $K^+π^-$, which is required to have an invariant mass within 100 MeV/ c 2 of the known $K^*$ (892) 0 mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb -1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q 2 , to be R K &#x2217;<!-- * --> 0 = { 0.66 &#x2212;<!-- - --> + 0.07 0.11 ( s t a t ) &#x00B1;<!-- ± --> 0.03 ( s y s t ) f o r 0.045 < q 2 < 1.1 G e V 2 / c 4 , 0.69 &#x2212;<!-- - --> + 0.07 0.11 ( s t a t ) &#x00B1;<!-- ± --> 0.05 ( s y s t ) f o r 1.1 < q 2 < 6.0 G e V 2 / c 4 . The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of $R_{K^{*0}}$ to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q 2 regions, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Resonances and $CP$ violation in $B_s^0$ and ${\overline{B}}_s^0\to J/\psi {K}^{+}{K}^{-}$ decays in the mass region above the $Φ(1020)$

The decays of $B_s^0$ and ${\overline{B}}_s^0$ mesons into the $J/ψK^+K^-$ final state are studied in the $K^+K^-$ mass region above the $Φ(1020)$ meson in order to determine the resonant substructure and measure the $CP$-violating phase, $Φ_s$, the decay width, $Γ_s$, and the width difference between light and heavy mass eigenstates, $ΔΓ_s$. A decay-time dependent amplitude analysis is employed. The data sample corresponds to an integrated luminosity of 3 fb -1 produced in 7 and 8 TeV pp collisions at the LHC, collected by the LHCb experiment. The measurement determines $Φ_s$ = 119 ± 107 ± 34 mrad. A combination with previous LHCb measurements using similar decays into the $J/ψπ^+π^-$ and $J/ψΦ(1020)$ final states gives $Φ_s$ = 1 ± 37 mrad, consistent with the Standard Model prediction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the Decays Λ b 0 → χ c 1 p K - and Λ b 0 → χ c 2 p K -

The first observation of the decays Λ$^0_b$ → $χ$ c1 $pK$ - and Λ$^0_b$ → $χ$ c2 $pK$ - is reported using a data sample corresponding to an integrated luminosity of 3.0 fb -1 , collected by the LHCb experiment in $pp$ collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured: $$\frac{\mathscr{B}(Λ^0_b→Χ_{c1}pK^-)}{\mathscr{B}(Λ^0_b→J/ψpK^-)}=0.242 ± 0.014 ± 0.013 ± 0.009$$ $$\frac{\mathscr{B}(Λ^0_b→Χ_{c2}pK^-)}{\mathscr{B}(Λ^0_b→J/ψpK^-)}= 0.248 ± 0.020 ± 0.014 ± 0.009$$ $$\frac{\mathscr{B}(Λ^0_b→Χ_{c2}pK^-)}{\mathscr{B}(Λ^0_b→Χ_{c1}pK^-)}= 1.02 ± 0.10 ± 0.02 ± 0.05$$ where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the $Χ_{c1}$ → $Jψγ$ and $Χ_{c2}$ → $Jψγ$ decays. Using both decay modes, the mass of the Λ$^0_b$ baryon is also measured to be $m$ Λ$^0_b$ = 5619.44 ± 0.28 ± 0.26 MeV/$c$ 2 , where the first and second uncertainties are statistical and systematic, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

First Observation of a Baryonic B s 0 Decay

We report the first observation of a baryonic $B$$_s^0$ decay, $B$$_s^0$ → $p$$\bar{Λ}$$K$ - , using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb -1 . The branching fraction is measured to be $B$($B$$_s^0$ → $p$$\bar{Λ}$$K$ - ) + $B$($B$$_s^0$ → $\bar{p}$$Λ$$K$ + ) = [5.46±0.61±0.57±0.50($B$)±0.32($f$ s /$f$ d )]×10 -6 , where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the $B$ 0 →$p$$\bar{Λ}$$π$ - decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of $b$-quark hadronization probabilities $f$ s /$f$ d .

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 the C P Violation Parameter A Γ in D 0 → K + K - and D 0 → π + π - Decays

Asymmetries in the time-dependent rates of D 0 →K + K - and D 0 →$π$ + $π$ - decays are measured in a $pp$ collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3 fb -1 . The asymmetries in effective decay widths between $D$ 0 and $\bar{D}$ 0 decays, sensitive to indirect $CP$ violation, are measured to be A $Γ$ (K + K - ) = (-0.30 ± 0.32 ± 0.10) × 10 -3 and A $Γ$ ($π$ + $π$ - ) = (0.46 ± 0.58 ± 0.12) × 10 -3 , where the first uncertainty is statistical and the second systematic. These measurements show no evidence for $CP$ violation and improve on the precision of the previous best measurements by nearly a factor of two.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the decay $Λ^0_b$ → $pK$ - $μ$ + $μ$ - and a search for $CP$ violation

A search for $CP$ violation in the decay $Λ^0_b$ → $pK$ - $μ$ + $μ$ - is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of CP violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of 3 fb -1 . The $Λ^0_b$ → $pK$ - $μ$ + $μ$ - decay is observed for the first time, and two observables that are sensitive to different manifestations of $CP$ violation are measured, $ΔΑ$ CP $\equiv$ $ΔΑ$ CP ($Λ^0_b$ → $pK$ - $μ$ + $μ$ - ) - $ΔΑ$ CP ($Λ^0_b$ → $pK$ - $J/Ψ$) and a C P T &#x005E;<!-- ^ --> - o d d , where the latter is based on asymmetries in the angle between the $μ$ + $μ$ - and $pK$ - decay planes. These are measured to be &#x0394;<!-- Δ --> A C P = ( &#x2212;<!-- - --> 3.5 &#x00B1;<!-- ± --> 5.0 ( s t a t ) &#x00B1;<!-- ± --> 0.2 ( s y s t ) ) &#x00D7;<!-- × --> 10 &#x2212;<!-- - --> 2 , a C P T &#x005E;<!-- ^ --> - o d d = ( 1.2 &#x00B1;<!-- ± --> 5.0 ( s t a t ) &#x00B1;<!-- ± --> 0.7 ( s y s t ) ) &#x00D7;<!-- × --> 10 &#x2212;<!-- - --> 2 , and no evidence for $CP$ violation is found

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for the Decays B s 0 → τ + τ - and B 0 → τ + τ -

A search for the rare decays $B^0_s$→$τ$ + $τ$ - and $B$ 0 →$τ$ + $τ$ - is performed using proton-proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3 fb -1 collected in 2011 and 2012. The $τ$ leptons are reconstructed through the decay $τ$ - →$π$ - $π$ + $π$ - $ν$ $τ$ . Assuming no contribution from B 0 →$τ$ + $τ$ - decays, an upper limit is set on the branching fraction $B$($B^0_s$→$τ$ + $τ$ - ) < 6.8×10-3 at the 95% confidence level. If instead no contribution from $B^0_s$→$τ$ + $τ$ - decays is assumed, the limit is $B$($B$ 0 →$τ$ + $τ$ - ) < 2.1×10 -3 at the 95% confidence level. These results correspond to the first direct limit on $B$($B^0_s$→$τ$+$τ$-) and the world's best limit on $B$($B$ 0 →$τ$ + $τ$ - ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for CP violation in the phase space of D 0 → π + π – π + π – decays

A search for time-integrated CP violation in the Cabibbo-suppressed decay D 0 → π + π – π + π – is performed using an unbinned, model-independent technique known as the energy test. This is the first application of the energy test in four-body decays. The search is performed for P-even CP asymmetries and, for the first time, is extended to probe the P-odd case. Using proton–proton collision data corresponding to an integrated luminosity of 3.0 fb –1 collected by the LHCb detector at centre-of-mass energies of $\sqrt{s}$ = 7 TeV and 8 TeV, the world's best sensitivity to CP violation in this decay is obtained. The data are found to be consistent with the hypothesis of CP symmetry with a p-value of (4.6±0.5)% in the P-even case, and marginally consistent with a p-value of (0.6±0.2)% in the P-odd case, corresponding to a significance for CP non-conservation of 2.7 standard deviations.

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