Study of ? ? ?-?-? ?0?0??

1
Study of ? ? ?-?-??0?0??

• Jenny Williams
• Manchester
• BaBar Tau Physics Workshop
• 6 December 2003

2
Some motivation

• Measurement of branching ratio for p-p-pp0p0
• Only one existing measurement (CLEO) 0.0055
  0.0004
• Study hadronic structure of final state, and BRs
  for sub-channels
• e.g. wp-p0, hp-p0, b1p, a1pp ...
• Contribution to studies of axial spectral
  functions
• Look for evidence for a JP 0- q-qbar-g hybrid
  state, suggested by Crystal Barrel at M ? 1500
  MeV, G ? 120 MeV
• Because its there

3

• Data and Monte Carlo Samples
• Analysis uses latest TauUser ntuples at
  Manchester (Run1 and Run2 with Release 10)
• Problems with RZOUT and copies to RAL, so only
  partial datasets so far analysed
• Samples used
• 53.3 fb-1 of data
• 74.4 fb-1 of generic tt- MC (67M events)
• 21.5 fb-1 of uds MC (44M events) ?
• 34.5 fb-1 of ccbar MC (45M events) ?

4

• Event, Track and Neutrals Selection
• Use 3-prong topologies in 1-3 and 3-3 TauUser
  events
• Stream19 pre-applied by TauUser
• 3-prong has net charge 1 and exactly 3 AWG
  charged tracks
• Selected events must have
• Thrust gt 0.92
• numPi0s lt 6
• Selected 3-prong hemispheres must have
• exactly 2 AWG p0s, each with E gt 300 MeV

5
Data/MC comparison of some distributions for
selected tracks and neutrals
All these plots normalised to the same area
6
Monte Carlo truth codes for selected 3-prong t s

• Code 10 p-p-pp0p0
• Code 20 hp-p0
• Overall signal efficiency e?? 6
• Code 5 a1 ? (p-p0p0 / p-p-p)
• Code 8 p-p-pp0
• Code 13 p-p-pp0p0p0

7
pp-p0 mass spectrum for M5p lt 1.8 GeV
5p mass spectrum
ppppp
hpp
Other t
uds
ccbar
8
w region in pp-p0 mass spectrum for M5p lt 1.8 GeV

• Fit (not shown) to w peak gives
• m 781.9 0.5 MeV
• ? 11.9 0.6 MeV
• Define peak and sideband regions as
• Peak m 2s
• Lower sideband -5s ? -3s
• Upper sideband 3s ? 5s
• Then peak minus sidebands defines bgd-subtracted
  signal

9
Dalitz plot density variable l

• ? (p p x p p- )2
• For w (JP1-) density is p(l) ? l
• For phase-space p(l) ? constant
• Looks fine in all samples except MC signal!

Peak minus bgd
MC signal
Bgd region
Peak region
10

• ? (p p x p p- )2
• Define JP1- weight as
• W 3 x (l-1)
• For p(l) ? l , average weight is 1
• For p(l) ? constant, average is 0
• pp-p0 mass spectrum, for
• M5p lt 1.8 GeV, weighted by W
• Shows W0 in signal MC (open hist) with other
  background features reproduced by non-signal MC

11

• wp-p0 mass spectrum using
• peak minus sidebands
• Problem with normalisation of uds?
• Distribution in data is broader than in MC signal
  (and broader than 120 MeV)
• Branching ratio in MC, based on CLEO result,
  looks slightly high (but these are early days)

12
p-p0 mass spectrum opposite w in data weights
(points) and bgd subtraction (hist)
p-p0 mass spectrum opposite w, using weights
Excellent agreement in data (but not in MC)
between weighting and background subtraction
13
Inclusive pp- mass spectrum
Inclusive pp0 mass spectrum
Generally good agreement, though more K0
and r in data
14
Helicity angle for w Normal to 3p decay plane in
w frame wrt to w in 5p frame
Peak region
Sideband regions
Peak - sidebands
15
Helicity angle for pp (r) system p direction
in r frame with respect to r direction in 5p frame
Peak region
Sideband regions
Peak - sidebands
16
Angle between p wrt r and w decay plane
normal wrt w
For data ratios (peak-bgd)/bgd for the
three angular distributions
Interesting non-isotropic distributions, not
reproduced by MC
17
What now?

• Use full Run1Run2 datasets with Release 12
• Use more and larger MC samples
• Improve cuts to enhance efficiency and purity
• Investigate kinematics/dynamics in Monte Carlo
  possibly use reweighting
• Measure branching ratios for 5p (including wpp,
  hpp ...)
• Produce a BAD by end 2003
• Spin-parity or amplitude analysis of constituent
  channels
• Include Run3 data
• Note for spring or summer conferences 2004
• Journal paper by end 2004