Тяжёлые адроны ФИАН / 9
.pdf
Z – charged exotic states
manifestly exotic since ccbar (bbar) state has 0 charge.
inner structure based on a simple quark–antiquark pair is completely excluded by the experimental data (decays into conventional charmonium states)
2008
2013: confirmed with larger stat. and full amplitude analysis (accounting for interference with K*)
full amplitude analysis the signal is not extracted just by fitting the invariant mass distribution, as done in the earlier mentioned analyses, but the amplitude of all the known (and unknown) processes which could lead at the same final states are summed up, taking into account different resonance parametrizations (such as energy-dependent widths), form factors, interference between intermediate states, spin and orbital quantum numbers, and finally used to fit the data. In this way it is possible to separate the contributions from different processes which overlap in the one dimensional distributions, thus to extract also the quantum numbers of unknown states.
11
Z – charged exotic states
LHCb analyzed the same decay with much larger statistics and full amplitude analysis
JP=1+
https://inspirehep.net/literature/1288881 Argand plot
12
Z – charged exotic states
BESIII and the Belle Collaborations
Observed peak in J/ψπ+ mass
JP = 1+
compact tetraquark ?
Decays into DD*
13
Zcs – charged exotic strange states
BESIII: |
recoil mass for Kaon |
https://inspirehep.net/literature/1830518
https://inspirehep.net/literature/2074678
14
Zb – charged exotic bottomonium states
Belle: |
peaks in hbπ and Yπ mass at 10.61 and 10.65 GeV |
Later also neutral Zb(10610)0
https://inspirehep.net/literature/900887
https://inspirehep.net/literature/939487 Decays into BB ? https://inspirehep.net/literature/1122970
15
D0 collaboration, 2016: observation of a new particle X(5568) decaying into B0sπ±
B0s 5582±100 events
Tetraquark candidate consisting of 4 different
quarks
10.1103/PhysRevLett.117.022003
Significance 3.9σ
R<0.3
Significance 5.1σ
NX = 133 ± 31
MX = 5567.8 ± 2.9 MeV
ΓX = 21.9 ± 6.4 MeV
D0 measured:
fraction of Bs0 mesons coming from X decays |
ρX =8.6±2.4% |
pT(Bs0) > 10 |
|
||||||||
|
|
|
|
|
ρ |
X |
=9.1±3.1% |
10<p |
T |
(B0)<15 |
|
|
|
|
|
|
|
|
|
s |
|
||
|
|
|
|
|
ρ |
X |
=8.2±3.1% |
15<p |
T |
(B0)<30 |
|
|
|
|
|
|
|
||||||
|
|
|
|
|
|
|
|
s |
16 |
||
|
|
|
|
|
|
|
|
|
|
|
|
X(5568) at LHCb
LHCb does not see it ! (however, in different kinematic region) Phys.Rev.Lett.117,152003(2016)
-30±77 |
87±62 |
|
LHCb set an upper limit:
ρX = 8.6±2.4% D0: ρX = 8.2±3.1%
pT(B0s) > 10 GeV
pT(B0s) > 15 GeV
17
Open beauty strange tetraquark X(5568)μ+
2012 data, 19.7 fb−1
B0 meson candidates are reconstructed |
https://inspirehep.net/literature/1643829 |
|
|
|
|
|
|
|
|
s |
|
|
|
|
via the decays Bs0→J/ψφ, φ→K+K−, J/ψ→μ+μ− |
|
|
|
|
Require B0 vertex to be significantly displaced from |
|
|
|
|
s |
|
π+ |
|
|
the PV, and its momentum to point from the PV |
|
B0 |
|
|
p |
|
p |
||
|
|
s |
K− K+
μ−
No significant peaks, both in the signal and in sidebands B0s regions
Additional pion is selected from tracks forming the primary vertex |
18 |
|
B0s π± invariant mass distribution
By removing the requirement on M(K+K−) to be consistent with φ mass, we allow the B0→J/ψK+π− decay to contribute to the reconstructed sample of J/ψK+K− candidates, into the signal and right sideband of B0s
In this case, the B0s π± distribution shows peaks from the B**+→B0π+ decays, which have exactly the same topology and very similar kinematics
https://inspirehep.net/literature/1643829
19
B0s π± invariant mass distribution
Different cross-checks include changes of the event selection (kinematic and reconstruction quality requirements), fit function, fit region, estimation of background from B0s sidebands, X signal sidebands, or simulation. In every case the signal yield is consistent with zero.
https://inspirehep.net/literature/1643829
20