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Observation in BaBar of a narrow resonance in the D + s p 0 system at 2317 MeV. Roger Barlow Manchester University For the B A B AR Collaboration. Data. 1999-2002 91 fb -1 On and off (4S) Search for D + s and p 0 : Require 3 tracks 2 photons over 100 MeV - PowerPoint PPT Presentation
Citation preview
Observation in BaBar of a narrow resonance in the D+
s 0 system at 2317 MeV
Roger BarlowManchester University
For the BABAR Collaboration
Roger Barlow: FPCP Paris 2003 Slide 2
Data
• 1999-2002• 91 fb-1
• On and off (4S)• Search for D+
s and : Require 3 tracks 2 photons over 100 MeV– FW moments H2/H0 <0.9
Roger Barlow: FPCP Paris 2003 Slide 3
selection
• Both E > 100 MeV
• fit probability >1%
• Neither shared with another candidate
Peak and sidebands
Roger Barlow: FPCP Paris 2003 Slide 4
selection(1
)
• Kaon id from DIRC & dE/dx via Neural network
• Vertex fit P>0.1%
sD
KKDs
Peaks from• D+(1869)
• D+s(1970)
• D*+(2010)D0+
D+
D+s
D*+
Roger Barlow: FPCP Paris 2003 Slide 5
• M(K+K-)<1.84 GeV• M(K+K-)M() or
M(K)M(K*) or K* decays with |
Cos h|>0.5• p*(K+K- + 0)>2.5
GeV
Signal and sidebands shown
80K D+s in signal region
sDselection(2
)
D+s
D+
Roger Barlow: FPCP Paris 2003 Slide 6
The signal
Large (unexpected) peak in D+
smass at 2.32 GeV
Named as D*sJ(2317)+
Small spike from D*+s just on
kinematic limit
?D+sJ(2317)
Roger Barlow: FPCP Paris 2003 Slide 8
Check# 2 Sidebands
0sidebands
No signal present
M(K+K- + 0) from sidebands in yellowD+
ssidebands
Roger Barlow: FPCP Paris 2003 Slide 9
Check# 3 Different D+
s
decaysSeen in both D+
s
and D+s K*K
Also in D+sK+K-
at the same mass
D+sJ(2317)
Roger Barlow: FPCP Paris 2003 Slide 10
Check# 4 Reflections
• Particle ID? – Take events: reassign K as . – No sign of D+ or D0 or D*
• D*+s(2112) D+
s+ extra
No: Antiselecting M(D+s 2112)
enhances peak at 2317
Roger Barlow: FPCP Paris 2003 Slide 11
Properties#1 p* dependence
Signal enhanced at high p*
As expected from e+ecc production
(Momentum of
D*+sJ(2317) in CMS)
Roger Barlow: FPCP Paris 2003 Slide 12
Properties#2 Mass
• Take p*>3.5 GeV• Gaussian +
polynomial• Peak at
2316.80.4 MeV• 126753 signal
events• Systematic
uncertainty below 3 MeV
Roger Barlow: FPCP Paris 2003 Slide 13
Properties#3 Width
• Single Gaussian • Standard Deviation
8.60.4 MeV• MC (revised) predicts
7.50.3 MeV• Measurement of
D+sK+K-+0 gives 6.7
0.1 MeV • Observed width
compatible with our mass resolution
10 MeV
Roger Barlow: FPCP Paris 2003 Slide 14
Properties#4 Angular Distribution
• Plot helicity angle of in D*+
sJ(2317) frame
• Correct for efficiency
Consistent with being flat:Suggests J=0. (Or unpolarised
and J=anything)
Roger Barlow: FPCP Paris 2003 Slide 15
Properties#5 Other modes
Not seen in– D+
s
– D*+s (2112)
– D+s
– D+s
– D+s
D*+s(2112)
Roger Barlow: FPCP Paris 2003 Slide 16
Comment onD+
s
Care needed!Peaks at Ds0 (2317) and
Ds(2112) combine to give reflection with M(Ds0 )2460
2112
2317
M(Ds)
M(Ds0)
• No peak at 2317• But new peak
appears at 2460• Enhanced when
M(D+s)2112=M(D
*+s)
Roger Barlow: FPCP Paris 2003 Slide 17
InterpretationA cs state: D*s
Below threshold for DK, D*K Ds decay violates isospin, hence narrowParity conservation JP=0+, 1-,2+…
0+ plausible from Cos distribution L=1 radial excitation. But other L=1 states (1+ and 2+) are at 2536, 2573Qq potential models predict 0+ at M=2480
2317 << 2480 Either re-think theory or include hybrid
Roger Barlow: FPCP Paris 2003 Slide 18
Confirmation
Confirmed by CLEO and BELLEMass and width and decay modes
consistent.
CLEO also claim D*+s(2463) in
D*+s(2112) 0
Roger Barlow: FPCP Paris 2003 Slide 19
The Peak in D*+
s
BaBar• There is a peak at 2.46 GeV• Some of it is a reflection of
the 2317. How much is still under study. Great care is required.
• Even if this peak is a resonance, it cannot account for all the 2317 signal
CLEO• There is a peak at 2.463
GeV• Some, but not all of it,
is a reflection of the 2317
• Some of the 2317 is a reflection of the 2463
If it exists, careful extraction of yields, masses and widths is needed. Work in progress…