2,621,898 research outputs found
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
No full textThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
Ab initio calculations on electron deficient molecules : boron hydrides and transition metal carbenes
No full textTypescript (photocopy).The effect of electron correlation on the electron distribution and bonding of diborane is examined in several basis sets. The generalized molecular orbital method is used to define optimized orbitals for the configuration interaction calculations. Electron correlation shifts electron density away from the hydrogens, both terminal and bridging, and into the interior of the cluster and increases the direct B-B contribution to the bonding. We have also calculated the dissociation energy of diborane (B(,2)H(,6) (--->) 2BH(,3)). The experimental value is 35 kcal mol('-1), while without electron correlation the theoretical value is only about 20 kcal mol('-1). Electron correlation increases the stability of the cluster by about 15 kcal mol('-1). Ab initio calculations of B(,5)H(,9), B(,5)H(,11), and 1,2-C(,2)B(,4)H(,6) have been performed in a double-(zeta) basis and with extended configuration interaction. Theoretical deformation densities are reported. Support is given for a postulated B-C-B open 3-center bond in 1,2-C(,2)B(,4)H(,6). Ab initio calculations are reported on several transition metal carbenes and their dissociated fragments. Results suggest electrophilic and nucleophilic metal carbenes arise from two different bonding schemes. Electrophilic, 18 electron, metal carbenes can be considered as bonding between singlet metal and singlet carbene fragments, whereas nucleophilic, often electron deficient, metal carbenes can be considered as bonding between triplet metal and triplet carbene fragments. The M=C dissociation energy for electrophilic (CO)(,5)Mo=CH(OH) is calculated to be 60 kcal mol('-1). The calculated M=C dissociation energy for nucleophilic CpCl(,2)Nb=CH(,2) is 72 kcal mol('-1). The latter compound appears to have a stronger (pi) bond. The calculated rotational barrier of the methylene in CpCl(,2)Nb=CH(,2) is 14.6 kcal mol('-1). The potential energy surface of the carbene in CpCl(,2)Nb=CH(,2) has been studied by ab initio techniques. M-C-H angles as small as 78(DEGREES) and M-C-R angles as large as 170(DEGREES) have been measured in metal alkylidenes, L(,n)M=CHR. Our calculations imply that these severe distortions are due to steric factors operating in a very flat potential energy surface. Distortions in 18 electron species are predicted to be smaller than in electron deficient species
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Measurement of b-hadron masses
No full textMeasurements of b-hadron masses are performed with the exclusive decay modes B +→J/ψK +, B 0→J/ψK +, B0→J/ψKS0, Bs0→J/ψφ and Λb0→J/ψΛ using an integrated luminosity of 35pb -1 collected in pp collisions at a centre-of-mass energy of 7 TeV by the LHCb experiment. The momentum scale is calibrated with J/ψ→μ +μ - decays and verified to be known to a relative precision of 2 ×10 -4 using other two-body decays. The results are more precise than previous measurements, particularly in the case of the Bs0 and Λb0 masses
The effect of chemical modification on the conformational stability of [beta]-lactoglobulin B
No full textTypescript (photocopy).To probe the relationship between chemical structure and conformational stability, the urea denaturation of bovine (beta)-lactoglobulin B and four chemically modified derivatives of this protein was investigated. The modifying groups were a series of mercaptans: mercaptopropionic acid, propanethiol, mercaptoethanol, and mercaptoethylamine; they were attached to the single sulfhydryl group of (beta)-lactoglobulin B through a disulfide bond. The reduced specific optical rotation, {(alpha)'}(,N), is -90.1(DEGREES) for (beta)-lactoglobulin B and the mercaptopropionic, propanethiol, and mercaptoethanol derivatives at 365.4 nm, the wavelength used to follow denaturation. In addition, the ORD spectra are similar in the near and far-UV wavelength range. This suggests that the conformation of these derivatives is similar to that of the unmodified protein. In contrast, for the mercaptoethylamine derivative, {(alpha)'}(,N) = -118.7(DEGREES) and the near and far-UV ORD spectra differ substantially. Thus, the conformation of this derivative differs substantially from that of the unmodified protein. In all cases, denaturation was shown to be reversible, and the derivatives were less stable than unmodified (beta)-lactoglobulin B. The midpoints of the isothermal urea denaturation curves at pH 2.83 and 25(DEGREES)C occur at 4.97 M urea for (beta)-lactoglobulin B, and 4.46 M, 4.23 M, 4.19 M, and 1.68 M urea for the mercaptopropionic acid, propanethiol, mercaptoethanol, and mercaptoethylamine derivatives, respectively. An analysis of this data shows that the corresponding decreases in the conformational stability are approximately 1.1, 1.6, 1.7, and 7.3 kcal/mole for the modified proteins
Measurement of the CKM angle gamma from a combination of B->Dh analyses
No full textA combination of three LHCb measurements of the CKM angle gamma is presented. The decays B->DK and B->Dpi are used, where D denotes an admixture of D0 and D0-bar mesons, decaying into K+K-, pi+pi-, K+-pi-+, K+-pi-+pi+-pi-+, KSpi+pi-, or KSK+K- final states. All measurements use a dataset corresponding to 1.0 fb-1 of integrated luminosity. Combining results from B->DK decays alone a best-fit value of gamma = 72.0 deg is found, and confidence intervals are set gamma in [56.4,86.7] deg at 68% CL, gamma in [42.6,99.6] deg at 95% CL. The best-fit value of gamma found from a combination of results from B->Dpi decays alone, is gamma = 18.9 deg, and the confidence intervals gamma in [7.4,99.2] deg or [167.9,176.4] deg at 68% CL, are set, without constraint at 95% CL. The combination of results from B->DK and B->Dpi decays gives a best-fit value of gamma = 72.6 deg and the confidence intervals gamma in [55.4,82.3] deg at 68% CL, gamma in [40.2,92.7] deg at 95% CL are set. All values are expressed modulo 180 deg, and are obtained taking into account the effect of D0-D0bar mixing
Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+
No full textAn analysis of B+ → K0
Sπ+ and B+ → K0
S K+ decays is performed with the LHCb experiment. The pp
collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass
energies of
√
s = 7 TeV and
√
s = 8 TeV, respectively. The ratio of branching fractions and the
direct CP asymmetries are measured to be B(B+ → K0
S K+
)/B(B+ → K0
Sπ+
) = 0.064 ± 0.009 (stat.) ±
0.004 (syst.), ACP(B+ → K0
Sπ+
) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0
S K+
) =
−0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at
√
s = 7 TeV is used to search for
B+
c
→ K0
S K+ decays and results in the upper limit ( fc · B(B+
c
→ K0
S K+
))/( fu · B(B+ → K0
Sπ+
)) <
5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b
quark
into a B+
c or a B+ meson, respectively
[Report to R. H. Lunday by B. M. Waters #1]
No full textReport by B. M. Waters, Detective in Charge, to R. E. Lunday, Deputy Chief Commanding of the Criminal Investigation Division. In the report, Waters describes a phone call received from Mr. James Hacker. Hacker believed that Oswald was paid to kill Governor Connolly by Jack Ruby
A s s e s s m e n t o f t h e L e v e l s o f P a r a t h y r o i d H o r m o n e , O e s t r o g e n a n d S e l e c t e d B o n e M i n e r a l s i n M e n o p a u s a l W o m e n
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