Tau Physics at BABAR

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Tau Physics at BABAR

• Jenny Williams
• University of Manchester
• BABAR UK Meeting, April 2004

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Tau Physics at BABAR
SM t Properties
Strange Decays
? ? pions
Beyond Standard Model

• Jenny Williams
• University of Manchester
• BABAR UK Meeting, April 2004

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Why study taus at BABAR?

• High cross section _at_ 10.6 GeV
• ??e?e? ? ????? ? 0.9 nb
• Low-multiplicity hadronic decays
• Clean environment for
• Precision studies of electroweak physics
• Searches for BSM decays

BR(??1prong) ? 85 BR(??3prong) ? 15
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Outline

• Since this is an internal meeting, I can give
  an idea of the present status of analyses and
  what results are coming soon
• Quick overview of TauQED AWG activities
• Whats being studied
• Current status and refs to analysis notes
• Few more details about some analyses

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1. Strange Decays

• ?? ? ??? ?t ? ????? ?t
• Andy (Manc) and Fabrizio (RHUL), see Andys talk
• ?? ? ?? ? ?t ? ?s?? ?t - first BABAR tau thesis
  in a while
• BAD829, aiming for Tau2004, Sept 04
• ? ? ????t , ??p?t , ?pp?t , ppp?t
• Ian Nugent (UVic)
• Fairly early in analysis basic event selection
  finalised
• Aims measurements of Vus, ms, precision tests
  of lattice QCD

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2. SM t properties t lifetime

• ? lifetime (decay length measurement)
• Alberto Lusiani (Pisa)
• Test of lepton universality
• Been around since 2000 BAD55, 83, 762
  (current), 30.2fb-1
• Main challenge SVT alignment
• Currently redoing analysis with 12-series data
  and kk2f MC

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SM t properties t neutrino mass

• M(nt) measurement
• ALEPH M(nt) lt 18.2 MeV
• Cosmological matter density M(nt) lt 0.7 eV
• Atmospheric neutrinos M(nt) gt 0.05 eV
• BABAR basic method
• Reconstruct hadronic decays of t and look at the
  high-mass region
• Compare with MC generated with various neutrino
  masses
• 3 analyses
• 5-prong t decays, BAD297
• Analysis stalled well developed, but needs
  man-power
• ? ? ??
• ? ? heavy hadrons ?t

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SM t m(nt) through ? ? ??

• ? ? ?? (Shane Curry, Irvine)
• Compare endpoint of energy spectrum with MC
• BR(????) 11.06 ? 0.11 (PDG)

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SM t m(nt) through ? ? H?

• M(nt) through ? ? H?, mH ? mt (Parker Lund,
  Irvine)
• Heavy hadronic states little energy left for
  neutrino
• Challenging analysis final states like a1r0
• Summed peak masses exceed t mass, but not in
  tails
• Final state resonances sought are very broad

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3. ? ? pions

• ?? ? p? p? p p0 p0 ?t
• Christina, George, Jenny, see Georges talk
• BAD788
• ?? ? r? ?t ? p? p0 ?t
• Mitch, George (continuation of analysis in
  BAD185)
• Measure branching ratio and contributions from
  radial excitations
• spectral function measurement important for
  determining corrections to g-2

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? ? pions ?? ? r-?t
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? ? pions ?? ? r-?t

• Finalise cuts to remove backgrounds
• Unfold detector effects from p-p0 mass spectrum
• Fit unfolded spectrum with r(770), r(1450) and
  r(1700)

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? ? pions ?? ? p ? p ? p p 0 ?t

• Second Class Current Search (?? ? p? p? p p0 ?t
  )
• Roger Barlow
• BAD327
• Updated for 12-series
• p0 studies ? AWG list
• Look for 2nd class currents
• Measure subchannel BRs
• Plot shows
• m(p? p p0 ) v m(p? p p0 )
• for both 3p combinations
• Bands are at the w(782) mass

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?? ? f p ? p 0 ?t ?
1
2
Plots show m( -) in data with K? mass 1 all
data 2 first track K id 3 second track K id 4
both tracks K id Bump/peak in K-id plots is at
f(1020) mass Smaller histos show Efreegt 0 MeV
Efree gt 100 MeV reduces signal/bgd does
not enhance peak ? looks like peak is signal
Mass of oppositely-charged track-pairs (GeV)
3
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? ? pions 5-prong decays

• ?? ? p? p? p? p p (n p0) ?t
• Randy Sobie (UVic), BAD note in progress
• Significant background from photon conversions
• Resonances found in data not modelled in Monte
  Carlo
• NEW BAD887,888

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? ? pions 7-prong ? decays

• ?? ? 7 prongs
• Ruben Ter-Antonyan and others (Ohio State)
• Blinded analysis at fairly early stage yet
• Signal discovery would strengthen bound on m(nt)
• Current theoretical limit lt 6 ? 10-11
• Assuming no narrow resonances in subchannels
• Current experimental limit lt 2.4 ? 10-6
• Challenge multi-prong decays not well modelled
  by MC
• Background estimated from blinded data

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? ? pions 7-prong ? decays
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4. Beyond Standard Model decays

• Lepton-flavour violation (neutrinoless t decays)
• Forbidden in the Standard Model
• Predicted to measurable levels in some SUSY
  models
• Observed in neutrino oscillations
• ?? ? e?g
• Rob Flack (RHUL) see Robs talk

• CP-violation
• Forbidden in lepton sector in Standard Model
• Predicted in some SM extensions
• Search for CP violation in ? - ? ? s p - ?t
• Mark Hodgkinson (Manc), Swagato (UVic), see
  Marks talk

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BSM Search for ? ? lll

• ? - ? l - l l - (l e,m 6 combinations)
• Olya Igonkina, Eric Torrence (Oregon)
• Phys.Rev.Lett.92121801,2004, hep-ex/0312027
• Supporting document BAD722
• Blinded analysis looking in DE-DM plane
• 91.5 fb-1, looking at 1-3 topology decays
• Results
• Limits (1-3) ? 10-7 at 90 confidence level
• (order of magnitude improvement over previous
  bounds)
• Belle, hep-ex/0403039, found comparable limits

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BSM LFV and CP violation searches

• ?? ? e?p?p?, e?p?K?, e?K?p?, e?K?K?, m?p?p?,
  m?p?K?, m?K?p?, m?K?K?, e?p?p?, e?K?p?, e?K?K?,
  m?p?p?, m?K?p?, m?K?K?, e?h, e?w, e?f, e?r, m?h,
  m?w, m?f, m?r
• Olya, Eric, 22 new neutrinoless channels
• Follow lll procedure lepton ID, reconstuct DM
  and DE
• Current upper limits (2-8)?10-6 (CLEO 5fb-1)
• Hope to improve on this an order of magnitude
• Currently fighting t and uds backgrounds

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BSM Search for ????

• ?? ? m?g
• Mike Roney and others (UVic)
• BAD455 (July 02)
• ???? enhanced by O(105-106)
• over ??e?
• Current theory limits
• SM mn ? O(10-34)
• SUSY ? O(10-6)
• Present 90 CL limits
• lt 1.1?10-6 (CLEO, 13.8 fb-1),
• lt 3.2?10-7 (Belle, 86.3 fb-1, prelim)
• lt 2.0?10-6 (BABAR, 56M t pairs, prelim)

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Summary

• Lots of t studies currently underway
• Many new results ready or in preparation
• 1 thesis finished
• 1 paper accepted for publication
• 4 new analysis BAD notes
• 7 analyses aiming for Tau2004, Nara, Japan, 14-17
  Sept 04
• Watch this space

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Other slides
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BSM ? ? lll systematics