x(3872) review
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X(3872) Review. T.Aushev LPHE seminar. Introduction. Era of the new family of particles, named XYZ, started from the observation of X(3872) in the J/ψ π+π- final state by the Belle experiment - PowerPoint PPT PresentationTRANSCRIPT
X(3872) Review
T.AushevLPHE seminar
8 February 2010 T.Aushev, LPHE seminar 2
Introduction
• Era of the new family of particles, named XYZ, started from the observation of X(3872) in the J/ψ π+π- final state by the Belle experiment
• Many new states have been found/observed/studied by Belle and other experiments, BaBar, CDF, D0, CLEO after that
• This is just a short list of them X(3872), X(3940), Y(3940), X(4160), Y(4008), Y(4260), Y(4350), Y(4660), Z(3930), Z(4415), Z(4430)+, Yb(10580), …• These particles are not fittable to any of the known or predicted states• Most probably it is new type of quark particles in addition to mesons
and baryon, although it is not proved yet
Observation of X(3872)
8 February 2010 T.Aushev, LPHE seminar 3
X(3872)'
M(+-l+l-)- M(l+l-) It did not fit to any known cc-bar statesMass of X(3872) is close to DD*
What is it: charmonium, DD*-molecule, tetraquark...?
Observed by Belle in B± → K± +-J/ 2003
Belle data: 152 M BB eventsMass = 3872.0±0.6±0.5 MeVSignificance = 10 σ
152M BB, PRL91, 262001(2003)
Most recent measurements
0803.2838 (2008)
0809.1224 (2008)
0906.5218 (2009)
0405004 (2004)
5.2σ
12.8σ (K+) + 5.9σ (KS)
(>> or = ∞) σ
8.6σ (K+) + 2.3σ (KS)
8 February 2010 T.Aushev, LPHE seminar 4
X(3872) mass measurements
8 February 2010 T.Aushev, LPHE seminar 5
Current mass is below the DD* threshold
• Recent CDF’s result is the most precise measurement of X(3872) mass• Together with CLEO’s update on the D0 mass gives hint on the X(3872) mass to be below the D0D*0 threshold
M(X(3872)), MeV/c2 Γ(X(3872)), MeV/c2
B→XK 3871.46±0.37±0.07 <2.3 @ 90% C.L. (2003)
B→XK 3871.4±0.6±0.1 <3.3 @ 90% C.L. (2008)
X→J/ψπ+π– 3871.61±0.16±0.19 1.34 (fixed from first two)
Our average 3871.50±0.19
M(D0)+M(D*0) 3871.81±0.36
Determination ofJPC
quantum numbersof the X(3872)
8 February 2010 6T.Aushev, LPHE seminar
JPC possibilities (for J ≤ 2)
0--
exotic
violates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
((3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed8 February 2010 7T.Aushev, LPHE seminar
Existence of X(3872) J/established:
C(X(3872))=+1
Belle, 275M BB, hep-ex/0505037(2005)
X(3872) C-parity
B± → K± J/
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Br(X →γJ /ψ )
Br(X →π +π −J /ψ )= 0.14 ± 0.05
no. of B’s in M(J/) bins13.6±4.4 ev. (4)
M=3872 MeV=13 MeV
J/ (2S)
€
Br(X →ψ (2S)γ)
Br(X →J /ψγ)= 3.4 ±1.4
Relatively large fraction of (2S) supports D*D molecule hypothesis and possible admixture of cc-bar component
BaBar, 465M BB, 0809.0042 (2009)
8 February 2010 T.Aushev, LPHE seminar 8
Isospin violation
B± → K± ( + - 0)J/
Further evidence for C(X(3872))=+1
If 3 come from , 2 – from large isospin violation, difficult to explain if X=cc state
5.200
virtual → + - 0
€
Br(X →π +π −π 0J /ψ )
Br(X →π +π −J /ψ )=1.0 ± 0.4 ± 0.3
8 February 2010 T.Aushev, LPHE seminar 9
JPC possibilities (for J ≤ 2)
0--
exoticviolates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
(y(3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(y2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed
8 February 2010 10T.Aushev, LPHE seminar
X(3872) P-parity
Looks like X(3872)→J/
P(X(3872))=+1
J/ : S wave
P wave
M( + -) from B± → K± + -J/
S wave: 2/dof=43.1/39 (CL=28%)
P wave: 2/dof=71.0/39 (CL=0.1%)
For C=+1: if P=+1 L({+-},J/)=0,2,…
P=-1 L({+-},J/)=1,3,…
M( + -) upper boundary is modulated by q2L+1 centrifugal barrier: S,P waves should dominate
55%7.7%
8 February 2010 T.Aushev, LPHE seminar 11
JPC possibilities (for J ≤ 2)
0--
exoticviolates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
(y(3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(y2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed8 February 2010 12T.Aushev, LPHE seminar
X(3872) properties (cont')
Angular distributions in B± → K± + -J/
Belle, hep-ex/0505038
side band
expectedJPC=0++
0++ (S, D waves)
+
-l+ l-
X(J/)
-
+K B
X(J/)
1++ (S, D waves)
Opposite parity 0-+ (P wave) has been also ruled out
JPC=0++, 1++, 2++ ?
|cos|
|cos|
JPC=1++
is disfavored
is favored
8 February 2010 T.Aushev, LPHE seminar 13
JPC possibilities (for J ≤ 2)
0--
exoticviolates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
(y(3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(y2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed8 February 2010 14T.Aushev, LPHE seminar
CDF study of quantum numbers
8 February 2010 T.Aushev, LPHE seminar 15
JPC possibilities (for J ≤ 2)
0--
exoticviolates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
(y(3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(y2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed8 February 2010 16T.Aushev, LPHE seminar
JPC possibilities (for J ≤ 2)
0--
exoticviolates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
(y(3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(y2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed8 February 2010 17T.Aushev, LPHE seminar
Quantum numbers summary
8 February 2010 T.Aushev, LPHE seminar 18
JPC = 1++ is the most favored1++ charmonium Xc1’ state is unlikely assignment for X(3872):
Potential model predicts Xc1’ mass to be 3953-3990 MeV/c2
Large isospin violation coming from BR(XJ/ψω)/BR(XJ/ψρ) ~ 1
J/ decay of ’c1 should be much stronger than isospin violating decay J/. Experimentally the ratio is 0.14±0.05.
Possible interpretation: X(3872) =D0D*0 molecule
DD* threshold enhancement in BKDD*
8 February 2010 T.Aushev, LPHE seminar 19
Both saw higher mass &BR(DD*) ≈ 10x BR(π+π-J/ψ)
PRD 77, 011102 (2008)
D0D00
Mass, MeV Width, MeV B+ BR x 104
Belle 3875.4±0.7+1.2-2.0 1.25±0.31±0.30
BaBar 3875.1+0.7-0.5±0.5 3.0+1.9
-1.4±0.9 1.67±0.36±0.47
PRL 97, 162002 (2006)
Higher X mass raised some speculations about new particle X(3875)
B→X(3872) K; X(3872)D*0D0; D*0D0 (γ,π0)
8 February 2010 T.Aushev, LPHE seminar 20
MD*D = (3872.9+0.6-0.4
+0.4-0.5) MeV
BaBar: (3875.1+0.7-0.5±0.5) MeV
Γ(Belle) =(3.9+2.8-1.4
+0.2-1.1) MeV
Γ(BaBar)=(3.0+2.5-1.3
+0.5-0.3) MeV
Nsig = 50.1+14.8-11.1
Significance = 6.4 σ
X(3872) mass shape is also well fittable by Flatte function
BR(BX(3872)(D*0D0)K) = (0.73±0.17±0.13)×10-4
NEW
hep-ex:0810.0358
2++ is rather unlikely (at least one D wave near threshold)
Charged and neutral partners of X(3872)
8 February 2010 T.Aushev, LPHE seminar 21
12.8
B0→XK0s
B+→XK+
5.9
X(3872)→J/ψπ+π–
diquark-antidiquark modelsXu and Xd from B0 and B+ decays
MX= 8±3 MeV Maiani et al PRD71, 014028
cdc dXd =
cdc d
cddcc dXd =
cuc uXu =
cuc u
cuucc uXu =
MX = (+0.18±0.89±0.26 ) MeV/c2 Br(B0→XK0) / Br(B+→XK+) = 0.82 ± 0.22 ± 0.05Br(B0→XK0) Br(J/–+) = (6.65 ± 1.63 ± 1.00)x10–6
Br(B+→XK+) Br(J/–+) = (8.10 ± 0.92 ± 0.66)x10–6
Molecule model
8 February 2010 T.Aushev, LPHE seminar 22
Most advanced theory which can explain all observed decay modes and their parameteris the molecule model.
According to it X(3872) is the D*0D0 state with bounding energy which make its mass below D*0D0 threshold.
It favors ten times larger BR to double charm in comparison with charmonium decays
Different models
8 February 2010 T.Aushev, LPHE seminar 23
X(3872) likely not a charmonium stateRadial excitation of χc1 (JPC = 1++) expected at 3950 MeV/c2
ηc2 (JPC = 2-+) should have X →J/ψγ suppressedNo satisfactory cc assignment
D0D*0 molecule? Phys. Rev. D71, 074005 (2005)
Would explain proximity of the D0D*0 thresholdfavors DD* decay over J/ψππ over J/ψγ (as observed)Expect X →ψ(2S)γ to be suppressed (in contradiction with observation)
tetraquark state? Phys. Rev. D71, 014028 (2005)
Predict 2 neutral states and 2 charged statesNeutral states produced in B0 and B+ decays: Δm ≈ (7 ± 2) MeV/c2
Measurements:Δm = (+0.18±0.89±0.26) MeV/c2 in B →J/ψπ+π-
No evidence for charged partners
Mixing of D0D*0 and χc1? Something else?...
Conclusion
• X(3872) is JPC=1++ state• Normal cc-bar charmonium can not be
assigned to this particle• Most probable nature is D0D*0 molecule with
probably admixture of normal cc-bar state
8 February 2010 T.Aushev, LPHE seminar 24