SLIDE 1
Rafael Silva Coutinho
UNIVERSITÄT ZÜRICH
University of Zurich On behalf of the LHCb experiment (including results from BaBar and Belle) June 06th, 2016 Flavour Physics and CP violation (FPCP) 2016
Experimental review of three-body
hadronic B-meson decays
SLIDE 2 Overview of recents 3-body decays results
- R. Coutinho (UZH) - FPCP 2016
Introduction to three-body decays analyses B decays to open charm, i.e. B → DhhÊ channels
[Dalitz-plot analysis, spectroscopy]
Status/issues foreseen for CPV measurements in charmless three-body charged decays
[Large CP violation seen in B± → h±h∓h± decays]
Final states involving K0S and/or π0Ês
[i.e. Β0(s)→ Κ0Sh±h’∓, Β0(s)→ h+h-π0, Β+→ Κ0Sh+h0decays]
b-baryon and Β+c decays
[Searches and CP violation measurements]
This talk covers some recent publications from hadronic three-body decays
2
SLIDE 3 Technique named after Richard Dalitz (1925-2006) Spin/parity determination of the known τ/θ particles in its decay products
„On the analysis of tau-meson data and the nature of the tau-meson.‰
Dalitz plot analysis
„I visualise geometry better than numbers‰
Richard Dalitz
Scatter-plot visualisation can be interpreted as: Matrix element is constant, i.e. DP uniformly populated with events Non-uniform distributions gives information about the dynamics Interference patterns between intermediate states can be studied and parametrised
- R. H. Dalitz, Phil. Mag. 44 (1953) 1068
„A work of art‰ - gift from B. Ritcher, W. Panofsky, S. Drell,
- D. Leith, D. Aston, W. Dunwmoodie and B. Ratcliff
SLAC-PUB-5151
- R. Coutinho (UZH) - FPCP 2016
3
SLIDE 4 ]
4
c /
2
) [GeV
−
π
S
K (
2
m
0.5 1 1.5 2 2.5 3
]
4
c /
2
) [GeV
+
π
S
K (
2
m
0.5 1 1.5 2 2.5 3
D0 → K0
Sπ+π−
(Non realistic simulation)
Dalitz plot analysis features
- R. Coutinho (UZH) - FPCP 2016
(m 23)max
1 2 3 4 5 2 4 6 8 10 m 12 (GeV2) m 23 (GeV2) (m 1+m 2)2 (M−m 3)2 (M−m 1)2 (m 2+m 3)2
(m 23)min
2 2 2 2
Particle Data Group Collaboration PRD 86 (2012) 010001
Toy simulation using Laura++ package: https://laura.hepforge.org
Intensity along bands indicates magnitude and the spin of the given resonance
Amplitude analysis can access: Relative phases between states Sensitivity to CP violating effects Resolve ambiguities in weak phases Hadron spectroscopy
4
SLIDE 5 Strong dynamics CP conserving
CP violating
cl : complex coefficients describing the relative magnitude and phase of the different isobars Fl : dynamical amplitudes that contain the lineshape and spin-dependence of the hadronic part
A possibility is to perform an „Isobar Model‰, in which the total amplitude is approximated as coherent sum of quasi-two-body contributions: Many observables can be accessed: Re(ci) and Im(ci) or |ci| and arg(ci); or derived quantities such as BF and ACP
Dalitz plot analysis - Isobar Model
- R. Coutinho (UZH) - FPCP 2016
Fl(L, m2
ij, m2 jk) = Rl(m2 ij) × XL(|~
p|r) × XL(|~ q|r) × Tl(L, ~ p, ~ q)
Resonance mass term (e.g. Breit–Wigner) Barrier factors - p, q: momenta
Angular probability distribution
A(m2
ij, m2 jk) = N
X
l=1
clFl(m2
ij, m2 jk)
5
SLIDE 6
B decays to open charm, i.e. B → DhhÊ channels
Charm and charm-strange spectroscopy
[PRL 113, 162001 (2014), PRD 90, 072003 (2014)] [PRD 91, 092002 (2015)] [PRD 92, 032002 (2015)]
Dalitz-plot analyses (e.g. spectroscopy and CKM angle measurements)
SLIDE 7 Mass (MeV)
1600 2000 2400 2800 3200
1S0
1979 2129 2673 2732 2484 3154 3193 2549 2556' 3018 3038' 2592 3048 2899 2900 2926' 2917 3208 3190 3186 3218'
3S1 3P0 P1 3P2 3D1 D2 3D3 3F2 F3 3F4
Ds Mass Spectrum
3005 3306 3298 3323' 3311
Spectroscopy of strange-charm states has been reinvigorated due to recent observations of Ds0*(2317) and Ds1(2460) DP analysis of B0s→Ds**-(D0K-)π+
Ds(**) spectroscopy - B0s → D0K-π+
PRD 89, 074023 (2014)
Stephen Godfrey, Ian T. Jardine
D∗
sJ(3040)−
D∗
sJ(2860)−
D∗
s1(2700)−
D∗
s2(2573)−
Ds1(2536)− Ds1(2460)−
D∗
s0(2317)−
D∗−
s
Ds
Some discrepancies have been seen between predicted and measured values
Ds* and Ds0*(2317) are too light to decay to D0K- Neither can states with unnatural spin-parity (JP = 0-, 1+, 2-, etc) Ds2*(2573), Ds1*(2700) and DsJ*(2860) are possible
- R. Coutinho (UZH) - FPCP 2016
7
SLIDE 8 Analysis performed with ~11K signal events and purity of 87%
Dalitz plot analysis of B0s → D0K-π+
- R. Coutinho (UZH) - FPCP 2016
PRD 90, 072003 (2014) PRL 113, 162001 (2014)
Signal region: µ2.5σ around nominal mass is considered for the Dalitz plot fit
Backgrounds due to Combinatorial (7.3%), B0 → D(*)0ππ (2.8%) and Λ0b → D(*)0pπ (2.3%)
]
4
/c
2
) [GeV
−
K D (
2
m
5 10 15 20 25
]
4
/c
2
) [GeV
+
π
−
K (
2
m
2 4 6 8 10 12
(a) LHCb
]
2
) [MeV/c
+
π
−
K D ( m
5200 5400 5600 5800
)
2
Candidates / (7 MeV/c
500 1000 1500 2000 2500
LHCb
Data Full fit signal
s
B Combinatorial bkg.
+
π
−
K D → B
+
π
−
K * D →
s
B
+
π
−
π *
( )0
D → B
+
π p *
( )0
D →
b
Λ 8
SLIDE 9 Dalitz plot fit results
]
2
) [GeV/c
−
K D ( m
2.4 2.6 2.8 3 3.2
)
2
Candidates / (9 MeV/c
50 100 150 200 250 300 350 400
(b) LHCb
]
2
) [GeV/c
−
K D ( m
2.5 2.55 2.6 2.65
)
2
Candidates / (1.5 MeV/c
20 40 60 80 100 120 140 160 180 200
(c) LHCb
]
2
) [GeV/c
−
K D ( m
2.75 2.8 2.85 2.9 2.95 3
)
2
Candidates / (5 MeV/c
5 10 15 20 25 30 35 40 45
(d) LHCb
]
2
) [GeV/c
+
π
−
K ( m
0.5 1 1.5
)
2
Candidates / (13 MeV/c
100 200 300 400 500
(a) LHCb
¯ K∗(892)0 ¯ K∗
0,2(1430)0
D∗
s2(2573)
D∗
sJ(2860)
- R. Coutinho (UZH) - FPCP 2016
PRD 90, 072003 (2014) PRL 113, 162001 (2014)
D∗
s2(2573)
D∗
sJ(2860)
9
SLIDE 10 Dalitz plot fit results - helicity projections
)
−
K D ( θ cos
0.5 1
Candidates / 0.04
50 100 150 200 250 300 350
2
) < 2.65 GeV/c
−
K D ( m 2.49 <
LHCb (b)
)
+
π
−
K ( θ cos
0.5 1
Candidates / 0.04
10 20 30 40 50 60 70
2
) < 1.5 GeV/c
+
π
−
K ( m 1.4 <
LHCb (d)
)
+
π
−
K ( θ cos
0.5 1
Candidates / 0.04
20 40 60 80 100 120 140 160
2
) < 1.0 GeV/c
+
π
−
K ( m 0.8 <
LHCb (b)
)
−
K D ( θ cos
0.5 1
Candidates / 0.04
5 10 15 20 25 30 35
2
) < 2.91 GeV/c
−
K D ( m 2.77 <
LHCb (d)
Vector Tensor Scalar + Tensor ??
- R. Coutinho (UZH) - FPCP 2016
PRD 90, 072003 (2014) PRL 113, 162001 (2014)
10
SLIDE 11 Several spin hypotheses have been investigated for the DsJ*(2860)- Two states [Ds1*(2860)-, Ds3*(2860)-] are required in the region 2.86 GeV/c2 (each with a significance of 10σ)
DsJ*(2860)- state
)
−
K D ( θ cos
0.5 1
Candidates / 0.04
10 20 30 40 50
LHCb
Data spin-1 + spin-3 spin-1 spin-3
Spin hypothesis ∆NLL √ 2∆NLL Masses and widths 1+3 — 141.0 16.8 2862 57 0+1 113.2 15.0 2446 250 2855 96 0+2 155.1 17.6 2870 61 2569 17 0+3 105.1 14.5 2415 188 2860 52 1 156.8 17.7 2866 92 1+2 138.6 16.6 2851 99 3134 174 2 287.9 24.0 3243 81 2 365.5 27.0 2569 17 2+3 131.2 16.2 2878 12 2860 56 3 136.5 16.5 2860 57
χ2 =47.3, 214, 150.0 Nbin = 50
1st observation of a heavy flavoured spin-3 resonance and 1st time a spin-3 state seen to be produced in B decay
- R. Coutinho (UZH) - FPCP 2016
PRD 90, 072003 (2014) PRL 113, 162001 (2014)
The presence of the state Ds3*(2860) has been independently confirmed in studies
- f pp → D*(+,0)K0,+X (LHCb)
[JHEP 02 (2016) 133]
11
SLIDE 12 ) [MeV]
+
π m(D 2200 2400 2600 2800 3000 Candidates / (4 MeV) 20000 40000 60000
LHCb
pull
5
2500 3000 2000 4000 6000
Charm spectroscopy at LHCb
- R. Coutinho (UZH) - FPCP 2016
JHEP 09 (2013) 145
Recent measurements of e+e-/𝑞𝑞 indicated the presence of higher excited states (both BaBar and LHCb)
PRD 91, 092002 (2015)
) [GeV]
−
π
+
D ( m
2 3 4
/ (0.054 GeV) 〉
6
P 〈
5 10 15
3
10 ×
(g) LHCb
States D*J(2650) and D*J(2760) seen to decay to Dπ
Initial investigation of angular moments to guide the modelling
No spin > 2 structure
B− → D+K−π− B0 → ¯ D0π+π− Two different DP fit framework: Isobar model and K-matrix parametrisation of the S-wave
PRD 92, 032002 (2015)
12
SLIDE 13
- R. Coutinho (UZH) - FPCP 2016
]
4
/c
2
[GeV
2
)
−
π D m(
7 8 9 10
)
4
/c
2
Events / ( 0.1 GeV
50 100 150 Data Isobar fit (2760)
* J
D
*
Other D
−
π
+
π Background LHCb (a)
DP analysis of B- → D+K-π-, B0 → D0π+π-
B− → D+K−π− ) [GeV]
+
D m(
2 3 4 5
Candidates / (40 MeV)
1 10
2
10
LHCb (b)
B0 → ¯ D0π+π−
Data favours spin-1 hypothesis for the state D*J(2760)0 (other assignments are rejected with > 6σ) Data strongly (10 σ) favours spin-3 assignment to the state D*J(2760)- No evidence for an additional spin-1
PRD 91, 092002 (2015) PRD 92, 032002 (2015)
13
SLIDE 14 Spectroscopy studies have received a great attention from the community with numerous recent results Addition insights can be obtained in near future through from B → D*hhÊ channels, where unnatural spin-parity states can appear Similar modes, e.g. B → D(*)D(*)h are of great interest (e.g. for leptonic decays)
- recently performed by BaBar [Phys. Rev. D 91, 052002 (2015)]
Measurements of CKM weak phases (i.e. γ, β and βs) are being gradually performed LHCb performed a simultaneous analysis of B0 → D0K+π-, with D0 → K+π- and
- f B0 → DCPK+π- (+cc) with DCP → π+π- or K+K- [arXiv:1602.03455]
Similar approach can be applied to other final states. Moreover, time-dependent amplitude analysis can provide clean measurements of mixing phases
Prospects/status for B → DhhÊ channels
- R. Coutinho (UZH) - FPCP 2016
14
SLIDE 15
LHCb results : L = 3 fb−1 − 2011 + 2012 dataset
Dalitz-plot analysis of B± → h±h∓hʱ decays, where h(Ê) ∈ {πµ, Kµ}
Large local phase-space asymmetries observed in charmless charged B decays
[PRD 90, 112004 (2014), PRL 112 (2014) 011801, PRL 111 (2013) 101801]
SLIDE 16 Local asymmetries - LHCb results
PRD 90, 112004 (2014)
Large local asymmetries observed in Bµ → hµh+h- with hµ ∈ {πµ, Kµ}
N raw
A
0.2 0.4 0.6 0.8 1
]
4
c /
2
) [GeV
−
K
+
(K
2
m
10 20
]
4
c /
2
) [GeV
−
π
+
(K
2
m
5 10 15 20 25
N raw
A
0.2 0.4 0.6 0.8 1
LHCb
N raw
A
0.2 0.4 0.6 0.8 1
]
4
c /
2
[GeV
low
)
−
π
+
π (
2
m
5 10 15
]
4
c /
2
[GeV
high
)
−
π
+
π (
2
m
5 10 15 20 25
N raw
A
0.2 0.4 0.6 0.8 1
LHCb
N raw
A
0.2 0.4 0.6 0.8 1
]
4
c /
2
) [GeV
−
π
+
π (
2
m
5 10 15 20
]
4
c /
2
) [GeV
−
π
+
(K
2
m
5 10 15 20 25
N raw
A
0.2 0.4 0.6 0.8 1
LHCb
N raw
A
0.2 0.4 0.6 0.8 1
]
4
c /
2
[GeV
low
)
−
K
+
(K
2
m
5 10 15
]
4
c /
2
[GeV
high
)
−
K
+
(K
2
m
5 10 15 20 25
N raw
A
0.2 0.4 0.6 0.8 1
LHCb
B± → K±π⌥π± B± → π±π⌥π± B± → K±K⌥K± B± → π±K⌥K±
- R. Coutinho (UZH) - FPCP 2016
]
2
c ) [GeV/
−
π
+
π ( m
0.5 1 1.5
)
2
Yield/(0.05 GeV/c
1 2 3
3
10 ×
LHCb
+
B
−
B
Opposite sign asymmetry
- bserved at low m2ππ and m2KK
Asymmetries as large as 60% in some regions!! Confirmed CP violation around the rho(770)0K+ as seen by Babar and Belle
16
SLIDE 17 PRD 90, 112004 (2014)
Sign of ACP (e.g. regions I-II) indicate interference between S- and P-wave importance Re-scattering may also play a role in the region between 1 and 1.5 GeV
B± → π±π⌥π±
- R. Coutinho (UZH) - FPCP 2016
]
2
c [GeV/
low
)
−
π
+
π ( m
0.5 1 1.5
)
2
Yield/(0.05 GeV/c
200 400 600 800 LHCb
+
B
−
B
]
2
c [GeV/
low
)
−
π
+
π ( m
0.5 1 1.5
)
2
Yield/(0.05 GeV/c
0.5 1 1.5
3
10 ×
LHCb
+
B
−
B
]
2
c [GeV/
low
)
−
π
+
π ( m
0.5 1 1.5
yields
+
100 200 300
LHCb
]
2
c [GeV/
low
)
−
π
+
π ( m
0.5 1 1.5
yields
+
100 200 300
LHCb
cos θ < 0 cos θ > 0
Local asymmetries - LHCb results
Dependence of asymmetry as function of invariant mass and helicity angle in regions around resonances
17
SLIDE 18 Full amplitude analysis is clearly the next step, in particular to understand the
- rigin of the strong phase difference
Such analyses are currently ongoing at LHCb! However, building models for these decays is challenging: Unprecedented statistics (e.g. 180K events for Bµ → Kµπ∓πµ): simplified theoretical descriptions are not sufficient to accommodate the data How to model the large non-resonant components? How to describe re-scattering effects? Connect two (or all) different final states? How to include thee-body final state interaction (FSI)? Very exciting field and fruitful dialogue with theory colleagues!
Large ACP in charmless B+ decays
- R. Coutinho (UZH) - FPCP 2016
18
SLIDE 19
Charmless three-body decays to final states containing K0S and/or π0Ês
Status and prospects for Dalitz-plot analyses
[JHEP 10, 143 (2013), arXiv:1501.00705]
Disclaimer: only a selection of results are shown here
SLIDE 20 u, d(s) ¯ b ¯ q1 u, d(s) h∓,0
2
¯ d, ¯ s q1 h±,0
1
B+, B0
(s)
W u, c, t g a
Final states containing K0S and/or π0Ês
Many channels have been already explored in the B-factories which has a great range
u, d(s) ¯ b ¯ u u, d(s) h∓,0
2
W q1 ¯ q2 h±,0
1
B+, B0
(s)
Transitions mediated by b → u (tree) and/or b → d,s (penguin) diagrams Several comparable amplitudes can give rise to (via interference) large CP violation Deviations of observables from their expected values in the SM could indicate NP contributions Potential to measure all three UT angles
[e.g. 𝛽-angle (Β0→ π+π-π0), 𝛾-angle (Β0→ Κ0Sπ+π-,Β0→ Κ0SΚ+Κ-]
Rich spectrum of final/resonant states can be further disentangled via amplitude analysis
- R. Coutinho (UZH) - FPCP 2016
20
SLIDE 21 ]
2
c ) [MeV/
−
π + π
S
K m(
5000 5200 5400 5600 5800
)
2
c Candidates / (16 MeV/
20 40 60 80 100 120 140 160
LHCb
S
K Downstream
First
Recent results for B0(s) → K0h+h’- decays
JHEP 10, 143 (2013)
]
2
c ) [MeV/
±
π
±
K
S
K m(
5000 5200 5400 5600 5800
)
2
c Candidates / (16 MeV/
20 40 60 80 100
LHCb
S
K Downstream
B0 → K0
Sπ+π−
B0
(s) → K0 SK±π⌥
First
- bservation
- R. Coutinho (UZH) - FPCP 2016
]
4
c /
2
) [GeV
±
K
S
K (
2
m
10 20 30
]
4
c /
2
) [GeV
±
π
S
K (
2
m
5 10 15 20 25 30
LHCb
±
π
±
K
S
K →
s
B
First observation of the Β0s→ Κ0Sπ+π- and Β0s→ Κ0SΚ±π∓ decays BF measurements of quasi-two-body states
[Β0s→ Κ*±h∓ - New J. Phys. 16 (2014) 123001] [Β0s→ K*0Κ0S - JHEP 01 (2016) 012]
Long term: time-dependent amplitude analysis to CKM-phases measurement Short term: time-integrated analysis [sensitive to CP in flavour-specific contributions]
21
SLIDE 22 Amplitude analysis of B+ → K0π+π0
Interesting theoretical motivations Sensitive to CKM phase γ Additional info to the Κπ „puzzle‰ Extremely challenging mode (1K signal events) with large backgrounds
- R. Coutinho (UZH) - FPCP 2016
Resonance Lineshape Parameters Resonance mass Width MeV/c2 MeV ρ(770)+ GS 775.5 ± 0.6 148.2 ± 0.8 K∗(892)+ RBW 891.7 ± 0.3 50.8 ± 0.9 K∗(892)0 RBW 896.1 ± 0.2 50.7 ± 0.6 (Kπ)∗0/+ LASS 1412 ± 50 294 ± 80 mcutoff = 1800 MeV/c2 a = 2.1 ± 0.1 (GeV/c)−1 r = 3.3 ± 0.3 (GeV/c)−1 )
2
(GeV/c
π
+
π
m
1 2 3 4 5
)
2
Events / (100 MeV/c
50 100 150
(f)
)
2
(GeV/c
π
S
K
m
1 2 3 4 5
)
2
Events / (100 MeV/c
50 100 150
(e)
)
2
(GeV/c
+
π
S
K
m
1 2 3 4 5
)
2
Events / (100 MeV/c
50 100 150
(d)
K∗(892) K∗
0(1430)
K∗(892) K∗
0(1430)
ρ(770)+
arXiv:1501.00705
∆AKπ
CP = ACP (K+π0) − ACP (K+π−) = 0.122 ± 0.022
22
SLIDE 23 B+ → K0π+π0 DP fit results
First measurement of inclusive BF K0π+π0 and K*+0(1430)« Remark: limited sensitivity to relative phases - difficulties to CKM constraint First evidence of CP violation in the decay channel Β+→ Κ*+π0 (3.4σ)!
- R. Coutinho (UZH) - FPCP 2016
arXiv:1501.00705
)
2
(GeV/c
+
π
S
K
m
1 2 3 4 5
)
2
Events / (100 MeV/c
20 40 60 80
(a)
)
2
(GeV/c
S
K
m
1 2 3 4 5
)
2
Events / (100 MeV/c
20 40 60 80
(b)
AK∗+π0
CP
23
SLIDE 24 Three-body decays with K0S/π0 summary
- R. Coutinho (UZH) - FPCP 2016
Although decays involving K0S in the final state can be complicate, neutral pions are much more experimentally challenging (but highly rewarding) Almost all of the existing DP analyses have come from BaBar, with exception
Inputs from Belle in the decays Β0 → Κ+π-π0 and Β+ → Κ0Sπ+π0 could provide important cross-checks For LHCb these modes will be particularly difficult LHCb has a great advantage in that it can perform time-dependent analyses
- f B0s decays, which Belle II cannot measure
Combine efforts of LHCb and Belle II is necessary: e.g. DP models may be more precisely extracted at Belle II, which can then be fed into time-dependent analyses at LHCb
24
SLIDE 25
LHCb results : L = 3 fb−1 − 2011 + 2012 dataset
Recent results in b-baryon and B+c three-body hadronic decays
Searches for Λ0b (Ξ0b) → Λh±h′∓ decays, including the two-body decay Λ0b → Λϕ
[JHEP 05 (2016) 08, arXiv:1603.02870 - submitted to PLB]
Search for the decay channel B+c → ppπ
[arXiv:1603.07037 - submitted to PLB]
SLIDE 26 Search for Λ0b(Ξ0b)→ Λh±h’∓ decays
JHEP 05 (2016) 08
d b d π− u d Λ Λ0
b
g π+ u s ¯ d ¯ u u u b u π+ d s Λ Λ0
b
W π− d u ¯ u ¯ d d
Among possible ground states with JP= ½+, only a single mode (Λ0b→ K0pπ-) had been observed No b-baryon mixing lead to a clean measurement
- f CP violation in the decay (self-tagging)
CP violation is yet to be observed in b-baryon Predictions vary in the range of 10-7 to 10-9 and are in general limited by the uncertainties
Studies of b-baryon decays is still at an early stage, although LHCb interesting has been significantly increasing
[PRD 69 017901 (2004), PRD 58 096013 (1998)]
- R. Coutinho (UZH) - FPCP 2016
[JHEP 04 (2014) 087]
[e.g. ACP (Λ0
b → K0pπ−) = −0.22 ± 0.13 ± 0.03]
26
SLIDE 27 Fit results for Λ0b(Ξ0b) →Λh+h- decays
- R. Coutinho (UZH) - FPCP 2016
First observation of the decays Λ0b → ΛK+π- (8.1σ) and Λ0b → ΛK+K- (15.8σ) with 3 fb-1 Decays involving an un-reconstructed π0 or photon are shown with the magenta and cyan lines, respectively
JHEP 05 (2016) 08
]
2
c ) [MeV/
±
π
±
K Λ ( m
5400 5600 5800 6000
)
2
c Candidates / ( 20 MeV/
10 20 30 40 50 60
LHCb
Λ0
b Yield : 97 ± 14
Ξ0
b Yield : 4 ± 7
]
2
c ) [MeV/
−
K
+
K Λ ( m
5400 5600 5800 6000
)
2
c Candidates / ( 20 MeV/
10 20 30 40 50 60 70 80 90
LHCb
Λ0
b Yield : 185 ± 15
Ξ0
b Yield : 4 ± 4
27
SLIDE 28 Fit results for Λ0b(Ξ0b) →Λh+h- decays
- R. Coutinho (UZH) - FPCP 2016
BF measured using as normalisation mode Λ0b → Λ+cπ- (471± 22)
Systematic are either dominated by the fit model/efficiency/Λ+cπ- yield (observed modes)
- r by the phase-space limited knowledge
]
2
c ) [MeV/
−
π
+
π Λ ( m
5400 5600 5800 6000
)
2
c Candidates / ( 20 MeV/
20 40 60 80 100
LHCb
Ξ0
b Yield : 19 ± 8
Λ0
b Yield : 65 ± 14
JHEP 05 (2016) 08 B(Λ0
b → Λπ+π−) = (4.6 ± 1.2 ± 1.4 ± 0.6) × 10−6
B(Λ0
b → ΛK+π−) = (5.6 ± 0.8 ± 0.8 ± 0.7) × 10−6
B(Λ0
b → ΛK+K−) = (15.9 ± 1.2 ± 1.2 ± 2.0) × 10−6
fΞ0
b/fΛ0 b × B(Ξ0
b → Λπ+π−) < 1.7 (2.1) × 10−6 at 90 (95) % CL
fΞ0
b/fΛ0 b × B(Ξ0
b → ΛK+π−) < 0.8 (1.0) × 10−6 at 90 (95) % CL
fΞ0
b/fΛ0 b × B(Ξ0
b → ΛK+K−) < 0.3 (0.4) × 10−6 at 90 (95) % CL
First observations: Evidence: Limits (No hints for any Ξ0b mode): Evidence for Λ0b → Λπ+π- (4.7σ)
28
SLIDE 29 CP asymmetry measurements
- R. Coutinho (UZH) - FPCP 2016
Significant signal observed allow measurements of phase-space integrated CP asymmetry CP asymmetry is measured to be: Results are consistent with CP symmetry and an update with Run 2 data is appealing!
JHEP 05 (2016) 08
Corrected raw asymmetry: Λ0b → Λ+cπ- control mode: negligible CP asymmetry Phase-space signal-corrected distribution of events
ACP = Araw
CP − (AP + AD)
ACP (Λ0
b → Λh+h
0−) = Araw
CP − Araw CP (Λ0 b → (Λπ+)Λ+
c π−)
ACP (Λ0
b → ΛK+π−) = −0.53 ± 0.23 (stat) ± 0.11 (syst)
ACP (Λ0
b → ΛK+K−) = −0.28 ± 0.10 (stat) ± 0.07 (syst)
29
SLIDE 30 ]
4
c /
2
) [GeV
−
K
+
K (
2
m
5 10 15 20
]
4
c /
2
) [GeV
+
K Λ (
2
m
5 10 15 20 25 30
LHCb
Dalitz-plot distributions
- R. Coutinho (UZH) - FPCP 2016
]
4
c /
2
) [GeV
−
π
+
K (
2
m
5 10 15 20
]
4
c /
2
) [GeV
+
K Λ (
2
m
5 10 15 20 25 30
LHCb
Λ0
b → ΛK+K−
Λ0
b → ΛK+π−
Interesting structures over the phase space, in particular the excess at low m(K+K−) consistent with a φ resonance (dedicated analysis at LHCb):
First observation (5.9σ) of the baryonic version of Β0s→ φφ
JHEP 05 (2016) 08
[arXiv:1603.02870]
B(Λ0
b → Λφ) = 5.18 ± 1.04 (stat) ± 0.35 (syst)+0.50 −0.43 (norm) ± 0.44(fd/fΛ0
b) × 10−6
30
SLIDE 31
LHCb results : L = 3 fb−1 − 2011 + 2012 dataset
Recent results in b-baryon and B+c three-body hadronic decays
Searches for Λ0b (Ξ0b) → Λh±h′∓ decays, including the two-body decay Λ0b → Λϕ
[JHEP 05 (2016) 08, arXiv:1603.02870 - submitted to PLB]
Search for the decay channel B+c → ppπ
[arXiv:1603.07037 - submitted to PLB]
SLIDE 32 In the SM, this process can only proceed via purely annihilation-type decay Any observation of BR higher than 10-8 could probe bc annihilation process BSM
Search for B+c → ppπ+ decays
arXiv:1603.07037
With the first observation of a number of B+c states, an extension to hadronic three-body charmless decays is natural
- R. Coutinho (UZH) - FPCP 2016
Experimentally similar to the companion B+ mode (reference)
)
2
) (GeV/c π p m(p
5.1 5.2 5.3 5.4
)
2
Candidates/(0.008 GeV/c
100 200 300 400 500 600 700
LHCb
B+ Yield : 1644 ± 83 32
SLIDE 33 )
2
) (GeV/c π p m(p
6 6.1 6.2 6.3 6.4 6.5
)
2
Candidates/(0.01 GeV/c
10 20 30 40 50
LHCb
)
2
) (GeV/c π p m(p
6 6.1 6.2 6.3 6.4 6.5
)
2
Candidates/(0.01 GeV/c
2 4 6 8 10
LHCb
)
2
) (GeV/c π p m(p
6 6.1 6.2 6.3 6.4 6.5
)
2
Candidates/(0.01 GeV/c
1 2 3 4 5 6 7
LHCb
Sensitivity of the measurement is enhanced by considering three MVA regions In the annihilation region, i.e. m(pp) < 2.85 GeV:
Search for B+c → ppπ+ decays
arXiv:1603.07037
- R. Coutinho (UZH) - FPCP 2016
Searches for the unobserved decays B+c → ppπ+ with BF relative to B+ → ppπ+
Region I Region II Region III
BDT output
0.2 0.4
Arbitrary units
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 Signal Background
LHCb
fc/fu × B(B+ → p¯ pπ+) < 3.6 × 10−8 at 95% CL
33
SLIDE 34 Prospects for b-baryon decays
- R. Coutinho (UZH) - FPCP 2016
Largely unexplored field up to now - LHC collisions produce copious b-baryons that provide the opportunity to Potential for extracting 𝛿 from open-charm decays to 3-body final, i.e. through the recently observed mode Λ0b → D0pK-
[PRD 89, 032001 (2014)]
First BF and ACP measurements of charmless decays starting to emerge
[e.g. JHEP 04 (2014) 087]
Many other channels are being studied (e.g. Ξ-b → ph-h-) Particularly interesting to see if these baryonic modes exhibit the large local CP asymmetries observed in Bµ → hµh∓hʵ decays Amplitude analyses are more complex than for the mesons, but much work is being done - theory predictions rather lacking for these modes
34
SLIDE 35 General conclusions
Enormous wealth of physics to be found in three-body hadronic decays
- f b-hadrons (e.g. CKM phase measurements, CP violation)
Some very interesting and intriguing results obtained recently in open- charm and charmless decays Latest results in multi-body charmless hadronic decays are using increasingly sophisticated amplitude analysis techniques Still many interesting results are foreseen with LHCb Run-I dataset (e.g. charmless DP analyses, b-baryon and B+c decays) Larger datasets from the LHCb upgrade and Belle II will provide in the future the possibility to fully explore the potential of the field
- R. Coutinho (UZH) - FPCP 2016
35
SLIDE 36 Dalitz plot fit results
- R. Coutinho (UZH) - FPCP 2016
PRD 90, 072003 (2014) PRL 113, 162001 (2014)
36
Contributions to the amplitude fit model (resonances labelled with subscript v are virtual) RBW = Relativistic Breit-Wigner, LASS = K« S-wave parameter from LASS experiment and EFF = exponential form factor
Floating parameters
Floating parameters + Multiple spin hypotheses
Floating parameters Floating parameters
SLIDE 37
- R. Coutinho (UZH) - FPCP 2016
DP analysis of B0 → D0π+π-
PRD 92, 032002 (2015)
37
]
4
/c
2
) [GeV
−
π D (
2
m
5 10 15 20 25
]
4
/c
2
) [GeV
−
π
+
π (
2
m
2 4 6 8 10
Entries
1 10
2
10 LHCb )
−
π D ( θ cos
0.5 − 0.5 1
Events / 0.1
5 10 15 20 25 30 35 40 Data (2760)
* J
No D Spin 0 Spin 1 Spin 2 Spin 3 Spin 4 LHCb (a) Isobar model
)
−
π D ( θ cos
0.5 − 0.5 1
Events / 0.1
5 10 15 20 25 30 35 40 Data (2760)
* J
No D Spin 0 Spin 1 Spin 2 Spin 3 Spin 4 LHCb (b) K-matrix model
Isobar K-matrix D∗
0(2400)
m 2349 ± 6 ± 1 ± 4 2354 ± 7 ± 11 ± 2 Γ 217 ± 13 ± 5 ± 12 230 ± 15 ± 18 ± 11 D∗
2(2460)
m 2468.6 ± 0.6 ± 0.0 ± 0.3 2468.1 ± 0.6 ± 0.4 ± 0.3 Γ 47.3 ± 1.5 ± 0.3 ± 0.6 46.0 ± 1.4 ± 1.7 ± 0.4 D∗
3(2760)
m 2798 ± 7 ± 1 ± 7 2802 ± 11 ± 10 ± 3 Γ 105 ± 18 ± 6 ± 23 154 ± 27 ± 13 ± 9
SLIDE 38 Large ACP in charmless B+ decays
- R. Coutinho (UZH) - FPCP 2016
)
2
Events / (0.015 GeV/c 20 40 60 80 100 120 )
2
Events / (0.03 GeV/c 20 40 60 80 100
)
2
(GeV/c
π π
m
0.6 0.7 0.8 0.9 1 1.1 )
2
Events / (0.03 GeV/c 20 40 60 80 100 120
)
2
(GeV/c
π π
m
0.7 0.8 0.9 1 1.1 1.2
20 40 60 80 100 120
Events/(20 MeV/c2)
B-→ K-π-π+ (a) B+→ K+π+π- (b)
20 40 60 80
Events/(50 MeV/c2)
B-→ K-π-π+ (c) cosθππ
H < 0
B+→ K+π+π- (d) cosθππ
H < 0
20 40 60 80 100 120 140 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
M(π+π-) (GeV/c2) Events/(50 MeV/c2)
B-→ K-π-π+ (e) cosθππ
H > 0
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
M(π+π-) (GeV/c2)
B+→ K+π+π- (f) cosθππ
H > 0
Many DP analyses of these modes have been performed by both Belle and Babar, e.g.
ACP (B+ → ρ(770)0K+) = (44 ± 10 ± 4 +5
−13)%
ACP (B+ → ρ(770)0K+) = (30 ± 11 ± 2 +11
−4 )%
[Phys. Rev. D 78, 012004 (2008)] [Phys. Rev. Lett. 96, 251803 (2006)]
38
SLIDE 39 ]
2
c ) [GeV/
−
K
+
K
−
(K m
5.1 5.2 5.3 5.4 5.5 ×
)
2
c Candidates / (0.01 GeV/
2 4 6 8 10 12
3
10 ×
LHCb
]
2
c ) [GeV/
−
K
+
K
+
(K m
5.1 5.2 5.3 5.4 5.5 ×
Model
−
K
+
K
±
K
→
±
B Combinatorial 4-body
→
B
−
K
+
K
±
π
→
±
B
−
π
+
π
±
K
→
±
B
]
2
c ) [GeV/
−
π
+
π
−
π ( m
5.1 5.2 5.3 5.4 5.5 ×
)
2
c Candidates / (0.01 GeV/
0.5 1 1.5 2 2.5 3
3
10 ×
LHCb
]
2
c ) [GeV/
−
π
+
π
+
π ( m
5.1 5.2 5.3 5.4 5.5 ×
Model
−
π
+
π
±
π
→
±
B Combinatorial 4-body
→
B
−
π
+
π
±
K
→
±
B
CP violation LHCb inclusive results
- R. Coutinho (UZH) - FPCP 2016
]
2
c ) [GeV/
−
π
+
π
−
(K m
5.1 5.2 5.3 5.4 5.5 ×
)
2
c Candidates / (0.01 GeV/
2 4 6 8 10 12 14 16 18
3
10 ×
LHCb
]
2
c ) [GeV/
−
π
+
π
+
(K m
5.1 5.2 5.3 5.4 5.5 ×
Model
−
π
+
π
±
K
→
±
B Combinatorial 4-body
→
B
±
)K γ ρ '( η
→
±
B
−
π
+
π
±
π
→
±
B
]
2
c ) [GeV/
−
K
+
K
−
π ( m
5.1 5.2 5.3 5.4 5.5 ×
)
2
c Candidates / (0.01 GeV/
0.2 0.4 0.6 0.8 1
3
10 ×
LHCb
]
2
c ) [GeV/
−
K
+
K
+
π ( m
5.1 5.2 5.3 5.4 5.5 ×
Model
−
K
+
K
±
π
→
±
B Combinatorial 4-body
→
S
B 4-body
→
B
−
K
+
K
±
K
→
±
B
−
π
+
π
±
K
→
±
B
ACP = +0.025 ± 0.004 ± 0.004 ± 0.007 ACP = −0.036 ± 0.004 ± 0.002 ± 0.007 ACP = +0.058 ± 0.008 ± 0.009 ± 0.007 ACP = −0.123 ± 0.017 ± 0.012 ± 0.007 PRD 90, 112004 (2014)
39
SLIDE 40 Channels with baryons in the final state are also of interest Pronounced enhancement in the near-threshold region Inclusive global ACP consistent with zero
]
4
c /
2
[GeV
p p 2
m
4 6 8
)
4
c /
2
)/(0.33 GeV
+
)-N(B
50 100 150
LHCb
]
4
c /
2
[GeV
p p 2
m
5 10 15 20
]
4
c /
2
[GeV
Kp 2
m
2 4 6 8 10 12 14 16 18
raw
A
0.05 0.1 0.15 0.2
LHCb
]
4
c /
2
[GeV
2 p p
m
5 10 15 20 25
]
4
c /
2
[GeV
2 p π
m
2 4 6 8 10 12 14 16 18 20
)
8
c /
4
Signal yield /(0.20 GeV
500 1000 1500 2000 2500 3000 3500
LHCb
]
4
c /
2
[GeV
2 p p
m
5 10 15 20
]
4
c /
2
[GeV
2 Kp
m
2 4 6 8 10 12 14 16 18 20
)
8
c /
4
Signal yield /(0.16 GeV
2000 4000 6000 8000 10000 12000
LHCb
m2
Kp < 10 GeV2/c4
m2
Kp > 10 GeV2/c4
Nsig = 18721 ± 142 Nsig = 1988 ± 74
PRL 113 141801 (2014) LHCb Collaboration
Local ACP observed
Baryonic final states
- R. Coutinho (UZH) - FPCP 2016
40
SLIDE 41 K0S reconstruction performed via two categories: Downstream (DD)
Dynamical structure of DP is correct non-uniform εsig over Veto intermediate open charm states: i.e. Ξ+c, D0, Λ+c Direct CP violation measurement is naturally available (simultaneous fit)
Long Track Downstream Track
Searches for the unobserved decays Λ0b(Ξ0b) → Λh±h’∓ (h(Ê) ∈ {πµ, Kµ}) BF relative to Λ0b → (Λ+cπ+)π-
dΓ ∼ |M|2 dE1 dE2 dα d(cos β) dγ
Analysis strategy for Λ0b(Ξ0b)→ Λh±h’∓
- R. Coutinho (UZH) - FPCP 2016
JHEP 05 (2016) 08
41
SLIDE 42 Search for the Λ0b → Λϕ decay
LHCb-ANA-2015-011
A natural extension of the previous analysis is the study of the possible intermediate resonant states
¯ u ¯ d ¯ b ¯ s ¯ u ¯ d ¯ Λ ¯ s s φ ¯ Λ0
b
W ¯ u, ¯ c, ¯ t g
Consider the golden channel model for the LHCb upgrade B0s → ϕϕ [CP violation in the interference between mixing and decay] Leading order diagrams is given by gluons loop transitions (many BSM theories accommodate non-zero CP violation) Equivalent b-baryon decay: Λ0b → Λϕ Measurement has already been performed in Λ0b → J/ψΛ decays (same spin structure) Can provide complementary information on the Λ0b polarisation, BRs and TPAs
- R. Coutinho (UZH) - FPCP 2016
42
SLIDE 43 Fit results for Λ0b → Λϕ decay
LHCb Unofficial LHCb Unofficial LHCb Unofficial LHCb Unofficial LHCb Unofficial LHCb Unofficial
(LL) (DD) (DD) (DD) (LL) (LL)
Very preliminary!
Λ0
b → KKpπ
φ → KK Λ → pπ Λ → pπ φ → KK
- R. Coutinho (UZH) - FPCP 2016
43
SLIDE 44 CP asymmetry measurements in Λ0b → Λϕ
- R. Coutinho (UZH) - FPCP 2016
arXiv:1603.02870
ˆ n = ~ p1 × ~ pΛ0
b
|~ p1 × ~ pΛ0
b|
As
φ = −0.07 ± 0.12 (stat) ± 0.01 (syst)
Ac
φ = −0.01 ± 0.12 (stat) ± 0.03 (syst)
As
Λ =
0.13 ± 0.12 (stat) ± 0.05 (syst) Ac
Λ = −0.22 ± 0.12 (stat) ± 0.06 (syst)
T-odd observables are accessible even without a full angular analysis (limited statistics available)
Asymmetries defined using the azimuthal angle Φi ∈ {Φ1, Φ2}, of the sines and cosines of this angle:
cos Φi = ~ eY · ~ ui sin Φi = ~ eZ · (~ eY × ~ ui) ~ ui = ~ eZ × ~ ni |~ eZ × ~ ni|
Only predictions (arXiv:hep-ph/0610189) for similar decay modes:
A(cos φ~
nΛ) = 4.3 %
A(sin φ~
nΛ) = −5.5 %
Λ0
b → ΛJ/ψ
Λ0
b → Λω
A(cos φ~
nΛ) = 2.4 %
A(sin φ~
nΛ) = −2.7 %
Asymmetries consistent with zero
44
