Bs Ds K

1
Bs ? Ds() K ()

• Plans for reconstructing Bs ? Ds() K ()
• Modes
• Bs ? Ds K
• Bs ? Ds K
• Bs ? Ds K
• and
• Bs ? Ds p

2
Branching fractions
Estimated branching fractions Bs ? Ds p-
(2.760.25) 10-3 from B?D- p Bs ? Ds()-
K (2.00.6) 10-4 from B?D- K Bs ? Ds() K-
(2.71.0) 10-5 from B?Ds p- (ratio
VubVcs/VcbVus0.37) Bs ? Ds- K (3.71.2)
10-4 from Bs?Ds-K using fK/fK (1) Bs ? Ds
K- (1.70.7) 10-5 from Bs?Ds()K- using
ratio(1) (1) Heavy flavours II, Non-leptonic
weak decays of B mesons, Neubert Stech
3
Subsequent decays
Ds ? K K- p (4.4) Ds ? Ds ?
(94.2) mDs1968.6 MeV Ds p0
(5.8) mDs2112.4 MeV (diff143.8
MeV) K ? K0 p (67) Of which half
decays to Ks0 K p0 (33)
4
Bs ? Ds K

• Recent work done only on Bs ? Ds K and Bs ? Ds p
• Used in TP, Reoptimization TDR, several theses.
• Recently, I tuned the preselection cuts.
• No analysis yet on Bs ? Ds K and Bs ? Ds K
• First plan is to try Bs ? (Ds?Ds ?) K, since
• asymmetry is expected same as Bs ? Ds K
• reconstruction efficiency same
• maybe soft photon is not needed to be
  reconstructed

5
Bs ? Ds K
What happens when photon is not
reconstructed? One can calculate the invariant
mass of the Ds K 5008 lt MDsK lt 5313 MeV 300
MeV mass window probably to big to reject enough
background (also Bs ? Ds- p) But it can be
used as pre-selection (no need to try to find
?). Trick Knowing the Ds- mass, and the
primary vertex, there are enough constraints to
fit the whole decay chain (so this includes the
momentum of the B, missing photon etc.)
6
Bs ? Ds K

• What happens if the p0 or Ks0 are not
  reconstructed?
• K ? Ks0 p 2256 lt MDsp lt 4546 MeV
• K ? K p0 3437 lt MDsK lt 5234 MeV
• Conclusion cannot select decay when p0 or Ks0
  are not found.
• Maybe decay chain trick works.?

7
Global vertex fit

• Recently a new vertex fitter was introduced
• Lagrange Global Fit
• Based on Lagrange multiplier method
• Vertex is also implemented as a constraint
• Mass constraints can be added
• Pointing constraints can be added
• Very generic, the whole decay chain can be
  fitted at once.

e.g. two tracks vertex constraint
8
Bs mass plots
Normal fit DsK invariant mass
Invariant mass plots with missing photon.
Calculated correction from constraints.
Global fit photon has huge error
9
Ds resolution
Normal mass constrained fit
Global mass constrained fit
x resolution
z resolution
? the normal mass-constraint vertex fit was wrong
for 3-particle vertices (there were only 2 vertex
constraints instead of 3).
10
LoKi
LoKi Toolkit to make selection of and
looping over Particles, and monitoring easier.

• Workflow
• Make the Particles (place particle ID cuts)
• Run LoKi algorithm to do the combinatorics(presel
  ection or final cuts)
• Run the efficiency algorithm (acceptance, reco
  and selection eff)
• Re-do trigger
• Tag the selected decay
• Run another LoKi algorithm to fill tuples and
  histograms(optionally tighten cuts)
• Save to (Mini)DSTWhen running over MiniDST only
  step 6 is needed.

11
Outlook

• New in Bs ? Ds K - tagging (find
  efficiency) - multiple PVs per event - new
  pre-selection
• About half of the decays have 1 or more short
  tracks. ?Try to select also these decays in Bs ?
  Ds() K ()
• Determine pre-selection and final cuts for Bs ?
  Ds K
• Determine efficiency on signal and background
• Determine tagging and trigger efficiency
• Determine resolutions (decay time)
• Try to reconstruct Bs ? Ds K