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تسجيل مستخدم جديدThe scalar kappa from D+ -> K- pi+ pi+: Further Studies
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Carla Gobel
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We briefly review the recent results obtained by Fermilab experiment E791 on the Dalitz plot analysis of the decay D+ -> K- pi+ pi+, where indication for a light Kpi scalar resonance, the kappa, was found. We also present preliminary studies providing further information on the phase behavior of the scalar components at low mass, supporting the previous indication for the kappa.
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We study the Dalitz plot of the decay D^+ --> K^- pi^+ pi^+ with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known K pi resonances and a uniform nonresonant term, we do not obtain an acc
eptable fit. If we allow the mass and width of the K^*_0(1430) to float, we obtain values consistent with those from PDG but the chi^2 per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797 +/- 19 +/- 43 MeV/c^2 and width 410 +/- 43 +/- 87 MeV/c^2. The mass and width of the K^*_0(1430) become 1459 +/- 7 +/- 5 MeV/c^2 and 175 +/- 12 +/- 12 MeV/c^2, respectively. Our results provide new information on the scalar sector in hadron spectroscopy.
Using proton-proton collision data collected by the LHCb experiment at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 1.0 fb^{-1}, the ratio of branching fractions of the B0 -> D*- pi+ pi- pi+ decay relative to the B0 -> D*- pi+ decay
is measured to be B(B0 -> D*- pi+ pi- pi+) / B(B0 -> D*- pi+) = 2.64 pm 0.04 (stat.) pm 0.13 (syst.). The Cabibbo-suppressed decay B0 -> D*- K+ pi- pi+ is observed for the first time and the measured ratio of branching fractions is B(B0 -> D*- K+ pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (6.47 pm 0.37 (stat.) pm 0.35 (syst.)) x 10^{-2}. A search for orbital excitations of charm mesons contributing to the B0 -> D*- pi+ pi- pi+ final state is also performed, and the first observation of the B0 -> Dbar_{1}(2420)^0 pi+ pi- decay is reported with the ratio of branching fractions B(B0 -> (Dbar_{1}(2420)^0 -> D*- pi+) pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (2.04 pm 0.42 (stat.) pm 0.22 (syst.)) x 10^{-2}, where the numerator represents a product of the branching fractions B(B0 -> Dbar_{1}(2420)^0 pi- pi+) and B(Dbar_{1}(2420)^0 -> D*- pi+).
The branching fractions of the doubly Cabibbo-suppressed decays $D^+rightarrow K^-K^+K^+$, $D^+rightarrow pi^-pi^+K^+$ and $D^+_srightarrowpi^-K^+K^+$ are measured using the decays $D^+rightarrow K^-pi^+pi^+$ and $D^+_srightarrow K^-K^+pi^+$ as norma
lisation channels. The measurements are performed using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2.0 fb$^{-1}$. The results are begin{align} frac {mathcal{B}(D^+rightarrow K^-K^+K^+)} {mathcal{B}(D^+rightarrow K^-pi^+pi^+)}& = (6.541 pm 0.025 pm 0.042) times 10^{-4}, onumber frac {mathcal{B}(D^+rightarrow pi^-pi^+K^+)} {mathcal{B}(D^+rightarrow K^-pi^+pi^+)}& = (5.231 pm 0.009 pm 0.023) times 10^{-3}, onumber frac {mathcal{B}(D^+_srightarrowpi^-K^+K^+)} {mathcal{B}(D^+_srightarrow K^-K^+pi^+)}& = (2.372 pm 0.024 pm 0.025) times 10^{-3}, onumber end{align} where the uncertainties are statistical and systematic, respectively. These are the most precise measurements up to date.
A new approach to the analysis of three body decays is presented. Model-independent results are obtained for the swave $Kpi$ amplitude as a function of $Kpi$ invariant mass. These are compared with results from $Kmpip$ elastic scattering, and the pre
diction of the Watson theorem, that the phase behavour be the same below $Keta^{prime}$ threshold, is tested. Contributions from $I=half$ and $I={3over 2}$ are not resolved in this study. If $I=half$ dominates, however, the Watson theorem does not describe these data well.}
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 Cabib
bo 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.
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