Study of $B^{-}to DK^-pi^+pi^-$ and $B^-to Dpi^-pi^+pi^-$ decays and determination of the CKM angle $gamma$

We report a study of the suppressed $B^-to DK^-pi^+pi^-$ and favored $B^-to Dpi^-pi^+pi^-$ decays, where the neutral $D$ meson is detected through its decays to the $K^{mp}pi^{pm}$ and CP-even $K^+K^-$ and $pi^+pi^-$ final states. The measurement is carried out using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 3.0~fb$^{-1}$. We observe the first significant signals in the CP-even final states of the $D$ meson for both the suppressed $B^-to DK^-pi^+pi^-$ and favored $B^-to Dpi^-pi^+pi^-$ modes, as well as in the doubly Cabibbo-suppressed $Dto K^+pi^-$ final state of the $B^-to Dpi^-pi^+pi^-$ decay. Evidence for the ADS suppressed decay $B^{-}to DK^-pi^+pi^-$, with $Dto K^+pi^-$, is also presented. From the observed yields in the $B^-to DK^-pi^+pi^-$, $B^-to Dpi^-pi^+pi^-$ and their charge conjugate decay modes, we measure the value of the weak phase to be $gamma=(74^{+20}_{-19})^{rm o}$. This is one of the most precise single-measurement determinations of $gamma$ to date.

Precision measurement of the mass and lifetime of the Xi_b^- baryon

We report on measurements of the mass and lifetime of the Xi_b^- baryon using about 1800 Xi_b^- decays reconstructed in a proton-proton collision data set corresponding to an integrated luminosity of 3.0 fb^{-1} collected by the LHCb experiment. The decays are reconstructed in the Xi_b^- --> Xi_c^0 pi^-, Xi_c^0 --> pK-K-pi+ channel and the mass and lifetime are measured using the Lambda_b^0 --> Lambda_c^+ pi- mode as a reference. We measure M(Xi_b^-) - M(Lambda_b^0) = 178.36 +- 0.46 +- 0.16 MeV/c^2 and tau(Xi_b^-)/tau(Lambda_b^0) = 1.089 +- 0.026 +- 0.011, where the uncertainties are statistical and systematic, respectively. These results lead to a factor of two better precision on the Xi_b^- mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations.

Precision measurement of the mass and lifetime of the $Xi_b^0$ baryon

Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb$^{-1}$ collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 $Xi_b^0toXi_c^+pi^-$, $Xi_c^+to pK^-pi^+$ signal decays are reconstructed. From this sample, the first measurement of the $Xi_b^0$ baryon lifetime is made, relative to that of the $Lambda_b^0$ baryon. The mass differences $M(Xi_b^0)-M(Lambda_b^0)$ and $M(Xi_c^+)-M(Lambda_c^+)$ are also measured with precision more than four times better than the current world averages. The resulting values are $frac{tau_{Xi_b^0}}{tau_{Lambda_b^0}} = 1.006pm0.018pm0.010$, $M(Xi_b^0) - M(Lambda_b^0) = 172.44pm0.39pm0.17 MeV/c^2$, $M(Xi_c^+) - M(Lambda_c^+) = 181.51pm0.14pm0.10 MeV/c^2$, where the first uncertainty is statistical and the second is systematic. The relative rate of $Xi_b^0$ to $Lambda_b^0$ baryon production is measured to be $frac{f_{Xi_b^0}}{f_{Lambda_b^0}}frac{{cal{B}}(Xi_b^0toXi_c^+pi^-)}{{cal{B}}(Lambda_b^0toLambda_c^+pi^-)}frac{{cal{B}}(Xi_c^+to pK^-pi^+)}{{cal{B}}(Lambda_c^+to pK^-pi^+)} = (1.88pm0.04pm0.03)times10^{-2}$, where the first factor is the ratio of fragmentation fractions, $btoXi_b^0$ relative to $btoLambda_b^0$. Relative production rates as functions of transverse momentum and pseudorapidity are also presented.

Measurement of the $bar{B}_s^0to D_s^-D_s^+$ and $bar{B}_s^0to D^-D_s^+$ effective lifetimes

The first measurement of the effective lifetime of the $bar{B}_s^0$ meson in the decay $bar{B}_s^0to D_s^-D_s^+$ is reported using a proton-proton collision dataset, corresponding to an integrated luminosity of 3 fb$^{-1}$, collected by the LHCb experiment. The measured value of the $bar{B}_s^0to D_s^-D_s^+$ effective lifetime is $1.379pm0.026pm0.017$ ps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light $bar{B}_s^0$ mass eigenstate of Gamma_L$=0.725pm0.014pm0.009$ ps$^{-1}$. The $bar{B}_s^0$ lifetime is also measured using the flavor-specific $bar{B}_s^0to D^-D_s^+$ decay to be $1.52pm0.15pm0.01 {rm ps}$.

First observations of $bar{B}_s^0to D^+D^-$, $D_s^+D^-$ and $D^0bar{D}^0$ decays

First observations and measurements of the branching fractions of the $bar{B}_s^0to D^+D^-$, $bar{B}_s^0to D_s^+D^-$ and $bar{B}_s^0to D^0bar{D}^0$ decays are presented using 1.0 fb$^{-1}$ of data collected by the LHCb experiment. These branching fractions are normalized to those of $bar{B}^0to D^+D^-$, $B^0to D_s^+D^-$ and $B^-to D^0D_s^-$, respectively. An excess of events consistent with the decay $bar{B}^0to D^0bar{D}^0$ is also seen, and its branching fraction is measured relative to that of $B^-to D^0D_s^-$. Improved measurements of the branching fractions ${cal{B}}(bar{B}_s^0to D_s^+D_s^-)$ and ${cal{B}}(B^-to D^0D_s^-)$ are reported, each relative to ${cal{B}}(B^0to D_s^+D^-)$. The ratios of branching fractions are {-0.2in} {center} {align*} {{cal{B}}(bar{B}_s^0to D^+D^-)over {cal{B}}(bar{B}^0to D^+D^-)} &= 1.08pm 0.20pm0.10, {{cal{B}}(bar{B}_s^0to D_s^+D^-)over {cal{B}}(B^0to D_s^+D^-)} &= 0.050pm 0.008pm0.004, {{cal{B}}(bar{B}_s^0to D^0bar{D}^0)over {cal{B}}(B^-to D^0D_s^-)} &= 0.019pm 0.003pm0.003, {{cal{B}}(bar{B}^0to D^0bar{D}^0)over {cal{B}}(B^-to D^0D_s^-)} &= 0.0014pm 0.0006pm0.0002,{{cal{B}}(bar{B}_s^0to D_s^+D_s^-)over {cal{B}}(B^0to D_s^+D^-)} &= 0.56pm 0.03pm0.04, {{cal{B}}(B^-to D^0D_s^-)over {cal{B}}(B^0to D_s^+D^-)} &= 1.22pm 0.02pm0.07, {align*} {center} oindent where the uncertainties are statistical and systematic, respectively.

First observation of the decays $bar{B}^0_{(s)}to D_s^+K^-pi^+pi^-$ and $bar{B}^0_sto D_{s1}(2536)^+pi^-$

The first observation of the decays $bar{B}^0_{s}to D_s^+K^-pi^+pi^-$ and $bar{B}^0to D_s^+K^-pi^+pi^-$ are reported using an integrated luminosity of 1.0 fb$^{-1}$ recorded by the LHCb experiment. The branching fractions, normalized with respect to $bar{B}^0_{s}to D_s^+pi^-pi^+pi^-$ and $bar{B}^0_{s}to D_s^+K^-pi^+pi^-$, respectively, are measured to be {br(bar{B}^0_{s}to D_s^+K^-pi^+pi^-)overbr(bar{B}^0_{s}to D_s^+pi^-pi^+pi^-)} &= (5.2pm0.5pm0.3)times10^{-2}, {br(bar{B}^0to D_s^+K^-pi^+pi^-)overbr(bar{B}^0_{s}to D_s^+K^-^pi^+pi^-)} &= 0.54pm0.07pm0.07, where the first uncertainty is statistical and the second is systematic. The $bar{B}^0_{s}to D_s^+K^-pi^+pi^-$ decay is of particular interest as it can be used to measure the weak phase $gamma$. First observation of the $bar{B}^0_sto D_{s1}(2536)^+pi^-, D_{s1}^+to D_s^+pi^-pi^+$ decay is also presented, and its branching fraction relative to $bar{B}^0_{s}to D_s^+pi^-pi^+pi^-$ is found to be {br(bar{B}^0_sto D_{s1}(2536)^+pi^-, D_{s1}^+to D_s^+pi^-pi^+)overbr(bar{B}^0_{s}to D_s^+pi^-pi^+pi^-)} &= (4.0pm1.0pm0.4)times10^{-3}.

First observation of the decays B0bar -->D+ K- pi+ pi- and B- --> D0 K- pi+ pi-

First observations of the Cabibbo suppressed decays B0bar -->D+ K- pi+ pi- and B- --> D0 K- pi+ pi- are reported using 35 pb^{-1} of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo favored decays, from which we obtain B(B0bar --> D+ K- pi+ pi-)/B(B0bar --> D+ pi- pi+ pi-)=(5.9pm1.1pm0.5) x 10^{-2} and B(B- --> D0 K- pi+ pi-)/B(B- --> D0 pi- pi+ pi-)=(9.4pm1.3pm0.9) x 10^{-2}, where the uncertainties are statistical and systematic, respectively. The B- --> D0 K- pi+ pi- decay is particularly interesting, as it can be used in a similar way to B- --> D0 K- to measure the CKM phase gamma.

Measurements of the Branching fractions for $B_(s) -> D_(s)pipipi$ and $Lambda_b^0 -> Lambda_c^+pipipi$

Branching fractions of the decays $H_bto H_cpi^-pi^+pi^-$ relative to $H_bto H_cpi^-$ are presented, where $H_b$ ($H_c$) represents B^0-bar($D^+$), $B^-$ ($D^0$), B_s^0-bar ($D_s^+$) and $Lambda_b^0$ ($Lambda_c^+$). The measurements are performed with the LHCb detector using 35${rm pb^{-1}}$ of data collected at $sqrt{s}=7$ TeV. The ratios of branching fractions are measured to be B(B^0-bar -> D^+pi^-pi^+pi^-)/ B(B^0-bar -> D^+pi^-) = 2.38pm0.11pm0.21 B(B^- -> D^0pi^-pi^+pi^-) / B(B^- -> D^0pi^-) = 1.27pm0.06pm0.11 B(B_s^0-bar -> D_s^+pi^-pi^+pi^-) / B(B_s^0-bar -> D_s^+pi^-) = 2.01pm0.37pm0.20 B(Lambda_b^0->Lambda_c^+pi^-pi^+pi^-) / B(Lambda_b^0 -> Lambda_c^+pi^-) = 1.43pm0.16pm0.13. We also report measurements of partial decay rates of these decays to excited charm hadrons. These results are of comparable or higher precision than existing measurements.