Beach04 Chicago Peter Kluit Excited B states at LEP Peter Kluit (NIKHEF) DELPHI/LEP Introduction &...
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Transcript of Beach04 Chicago Peter Kluit Excited B states at LEP Peter Kluit (NIKHEF) DELPHI/LEP Introduction &...
Beach04 Chicago Peter Kluit
Excited B states at LEP
Peter Kluit (NIKHEF)
DELPHI/LEP
• Introduction & history • Theory• Experimental overview• Excited Bu,d results• Search for Bs
** and b(*)
• Summary
Beach04 Chicago Peter Kluit
Introduction History
Boom of B physics at LEP
around 1994
• vertex detectors
• exclusive reconstruction
Discovery Bs meson at LEP
B baryons
Precision lifetimes
Bd oscillations Event Bs→ `→KK
Beach04 Chicago Peter Kluit
Inclusive B reconstruction
New technique (~1994)
• High rapidity particles
• Secondary vertex
• Energy-momentum constraint
Estimate B four-momentum
Physics result:
precision mass B*→B
Production V/(V+P)=0.75
→e+e-
Beach04 Chicago Peter Kluit
Discovery of excited B states
Reconstruct B**→B
Inclusive B
fragmentation
OPAL 1995
Prel. 1997
Prel. 1997
Bs**b
(*)
OPAL 1995
1995
Beach04 Chicago Peter Kluit
Theory HQET
l jq JP state Decay
0 ½ 0-
1-
BB* B
1 ½ 0+
1+
B*0
B*1
BB*
1
3/2
1+
2+
B1
B*2
B*B(*)
Heavy Q, light quark q
sq l → jq; sQ jq → J
Charm system measured:
Broad
NarrowExpect B systemm doublet ~mc mc/mb
~13 MeV
Broad y 300 MeV
• Similar for Bs**, decay to Bs* Isospin forbidden
• Dominant decay Bs**→ B(*) K, if above threshold
Beach04 Chicago Peter Kluit
B production at LEP
production fractions adjusted to world average
Beach04 Chicago Peter Kluit
Experimental overview Bud**
Experiment method m(B**) MeV (B**)/(b) OPAL 95 Incl 5712 ± 11 0.22 ± 0.05 DELPHI 95 Incl 5732 ± 5± 20 0.27±0.02±0.06
ALEPH 96 Incl 5734 ± 3 ± 16 0.14±0.01±0.03
L3 99 Incl B*2: 5768±5±6 0.32±0.03±0.06
CDF 01 Semi-excl B1: 5710 ± 20 0.22±0.05±0.02
ALEPH 98 Excl B*2:5739±11±6 0.24±0.07±0.05
Some numbers recomputed
using common inputsOPAL 01 Br(B**→B* X)=0.85±0.26±0.12
Narrow states
Beach04 Chicago Peter Kluit
Experimental issues
• Crucial treatment of background
• Taken from MC, except ALEPH exclusive analysis
• Induces high production rate, shifted mass peaks, instabilities
ALEPH exclusive
Beach04 Chicago Peter Kluit
New DELPHI B** analyses
Focus on the background
• using control sample: High efficiency
• Reduction by neural networks: High purity
Full LEP I statistics, reprocessed data, improved analysis techniques, inclusive B reconstruction
b and anti b tagging
B charge
Beach04 Chicago Peter Kluit
Analyses steps
• Reconstruct weakly decaying B and combine with from primary vertex
Signal Background wrong sign
Bd** →B+ B+
Bu**+ →B0 B0
• Samples separated b/b tag B vertex charge
• High Efficiency: soft cuts, signal/wrong sign similar shape
• High Purity: tight cuts, neural network
Beach04 Chicago Peter Kluit
High efficiency Analysis• Simultanous fit to signal and background
B** signal
Narrow: B*2 mass and m(B*2-B1) free
Br(B*2 →B*/B±0.3
Broad: extrapol from Charm
m(B*1)=m(B1),m(B1-B0)=45 MeV
=300(330) MeV
Enhancement at Q~500 MeV, ~300 MeV (~2 s.d.)
DELPHI
Beach04 Chicago Peter Kluit
High purity analysis• Fit background MC times polynome
• Signal resolution free parameter
Largest Systematics
• Background parametrisation
• Energy scale
• Cuts NN rapidity
• Modeling:
With/without 500-state
Spin/state counting
Fits not sensitive to Broad states and to spin/state counting (< 2 s.d.)
Significant deviations MC
at low and high Q values
B0
B+
Beach04 Chicago Peter Kluit
Summary of B** results• Total rate (B**ud)/(b) (broad+narrow)
Meth Total rate Narrow rate Q( B*2 ) MeV
m(B*2-B1) MeV
HEff 0.160±0.012
±0.020±0.025
0.091±0.007
±0.013±0.011
316±9
±12±9
-2±15±9±11
HPur 0.153±0.017
±0.038±0.017
0.088±0.009
±0.022±0.011
323±7
±13±9
15±13±10±6
Comb 0.157±0.011
±0.022±0.019
0.090±0.007
±0.013±0.011
319±6
±9 ±9
6±11±7±6
(stat) (sys) (model)
m(B*2)=5738 ± 14 MeV and m(B1)=5732 ± 20 MeV
DELPHI preliminary
Beach04 Chicago Peter Kluit
Comparison of LEP Results• Rate (B**ud)/b) (narrow)~factor 1.5-2 lower
• Due to background treatment, inclusive analyses at LEP overestimate the rate
• Compatible with ALEPH exclusive analysis
m(B*2)=5739 ± 10 MeV DELPHI:5738 ± 14 MeV
Total rate=0.24±0.07±0.05 DELPHI:0.157±0.011±0.029
• Compare to (D**narrow)/(c) = 0.17 ±0.05
• FUTURE recommend exclusive analyses extracting the background from data
Beach04 Chicago Peter Kluit
DELPHI B**s search • Channel Bs
** → B(*)+ K-
•Using neural networks for identification of kaon and B vertex charge
•Fit signal (Gaussian), free background
Total Significance 3.8
systematics included
•Background shape
•Identification K/ NN
•Energy scale
Beach04 Chicago Peter Kluit
Interpretation & discussion• Most likely Bs2
* → B K-
(B*K reduced by factor 10)
Bs1 Puzzle: Large m? Enhanced Bs1 → Bs*?
Results m(Bs2*)=5852 ± 5 MeV OPAL: 5800-5900 MeV
Rate (Bs2*)/(b)=0.0093±0.0020±0.0013 OPAL: 0.020 ±0.006
Where is Bs1 → B*K?
m 13 MeV
DELPHI preliminary
Beach04 Chicago Peter Kluit
DELPHI b(*) search
• Channel b± (*)→b±
• Using neural networks for identification B baryon
• Fit signal, free background
Sqq J
b 0 ½b 1 ½b
* 1 3/2
Upper limit 95% CL
(b(*))/(b) < 0.012
Preliminary
Old prel. DELPHI result
not confirmed
Beach04 Chicago Peter Kluit
Summary• New DELPHI measurements for B**ud
Total production rate: (B**ud)/(b)=0.157±0.011±0.029
m(B*2)=5738 ± 14 MeV and m(B1)=5732 ± 20 MeV
New results ~factor 1.5-2 lower than previous due to background
Compatible with ALEPH exclusive, and charm production
• Search for B**s
Signal at 3.8 with m(Bs2*)=5852 ± 5 MeV; Bs1 Puzzle
Production rate: (Bs2*)/(b)=0.0093±0.0020±0.0013
• Search for b(*)
Limit production rate:(b(*))/(b) < 0.012 at 95% CL
Pre
limin
ary