Beauty hadron decays at LHCb
Decays of Bc+ and b-baryons
Anton Poluektov
The University of Warwick, UK
Budker Institute of Nuclear Physics, Novosibirsk, Russia
5 May 2016
On behalf of the LHCb collaboration
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
1/17
b-baryon and Bc+ decay data
→
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
2/17
Introduction
Other b-baryonic results: talks on spectroscopy [Daniel Craik], b → s penguins
[Konstantinos Petridis], |Vub | [Basem Khanji], charmless decays [Giulio Dujany];
Bc+ : poster by [Liupan An]
Production and properties of b-baryons
Production of Λ0b and B 0 hadrons in pp collisions and first measurement of the
Λ0b → J/ψ pK − branching fraction
Measurement of the properties of the Ξ0b ∗ baryon
Measurement of the mass and lifetime of the Ω−
b baryon
b-baryon decays
Observation of Λ0b → ψ(2S)pK − and Λ0b → J/ψ π + π − pK − decays and
measurement of Λ0b baryon mass
Search for the Λ0b → Λη 0 and Λ0b → Λη decays
0 −
Evidence for the strangeness-changing weak decay Ξ−
b → Λb π
Bc+ decays
Measurement of branching fraction ratio B(Bc+ → ψ(2S)π + )/B(Bc+ → J/ψ π + )
Search for Bc+ → ppπ + final state
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
3/17
b-baryons
l=0 q1
l=0 q1
q
2
l=0 q1
q
2
L=0
b
Ground-state
baryons
Y
−
Ξb
dsb
- unobserved
2
L=0
b
b
Y
−
Λ0b
udb
- observed
q
L=0
Σb
ddb
Ξ0b
usb
'−
I3
Y
Σ0b
udb
Ξb
dsb
*−
Σ+b
uub
Ξ'0
b
usb
Σb
ddb
Σ*0
b
udb
*−
Ξb
dsb
I3
0
CMS
[PRL 108 (2012) 252002]
Ξb− , Ξ∗−
b : LHCb
[PRL 114 (2015) 062004]
Four still hiding
(final state involves soft neutral particles)
Ξ*0
b candidates per 2 MeV
Ξ∗0
b :
j=1, JP=3/2+
16
14
Beauty hadron decays at LHCb
CMS
pp, s = 7 TeV
Opposite-sign data
L = 5.3 fb-1
Signal+background fit
12
10
Background
(b)
8
6
4
2
0
0
Anton Poluektov
I3
Ωb
ssb
j=1, JP=1/2+
Three of them discovered recently at LHC:
Ξ*0
b
usb
*−
−
Ωb
ssb
j=0, JP=1/2+
Σ*+
b
uub
10
20
30
40
50
M(J/ψΞ π+) - M(J/ψΞ ) - M(π) [MeV]
Beauty 2016, Marseille, France, 1 – 6 May 2016
4/17
b-baryons
l=0 q1
l=0 q1
q
2
l=0 q1
q
2
L=0
b
Ground-state
baryons
Y
−
Ξb
dsb
- unobserved
2
L=0
b
b
Y
−
Λ0b
udb
- observed
q
L=0
Σb
ddb
Ξ0b
usb
'−
I3
Y
Σ0b
udb
Ξb
dsb
*−
Σ+b
uub
Ξ'0
b
usb
Σb
ddb
Σ*0
b
udb
*−
Ξb
dsb
I3
Ξb− ,
Ξ∗−
b :
[PRL 108 (2012) 252002]
LHCb
[PRL 114 (2015) 062004]
Four still hiding
(final state involves soft neutral particles)
j=1, JP=3/2+
140
Entries per 0.1 MeV/c2
0
Entries per 0.45 MeV/c2
Ξ∗0
b : CMS
I3
Ωb
ssb
j=1, JP=1/2+
Three of them discovered recently at LHC:
Ξ*0
b
usb
*−
−
Ωb
ssb
j=0, JP=1/2+
Σ*+
b
uub
120
100
80
35
30
25
20
15
10
5
0
2
LHCb
3
4
60
5
δm [MeV/c2]
Ξ0bπ−
Ξ0bπ+
40
20
0
0
10
20
30
40
δm [MeV/c2]
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
4/17
Production of Λ0b and B(Λ0b → J/ψ pK − )
b-baryons (predominantly Λ0b ) are produced abundantly in pp collisions. Ratio fΛ0 /fd
b
ranges from 0.6 (low pT ) to 0.2 (high pT )
[JHEP 08 (2014) 143]
−
0
+ −
decays.
fΛ0 /fd (pT ) was measured before with Λ0b → Λ+
c µ ν µ and Λb → Λc π
b
Λ0b → J/ψ pK − decay mode:
[Chin. Ph. C 40 (2016) 011001]
Higher trigger efficiency (especially at low pT )
Measured B allows to obtain B for decays to pentaquark states [Talk by D. Craik]
Normalisation for other charmonium modes
Measured wrt B 0 → J/ψ K ∗0
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
5/17
Production of Λ0b and B(Λ0b → J/ψ pK − )
[Chin. Ph. C 40 (2016) 011001]
RΛ0/ B0
0.2
0.2
LHCb
b
LHCb
b
RΛ0/ B0
Ratio of Λ0b /B 0 production as functions of pT and rapidity y [Talk by S. Barsuk]
0.15
0.15
0.1
0.1
0.05
0
0
7 TeV data
7 TeV fit
8 TeV data
8 TeV fit
5
10
0.05
7 TeV data
8 TeV data
15
20
p [GeV/c]
0
2
2.5
3
3.5
4
T
4.5
y
Production dependence has to be taken into account in B(Λ0b )/B(B) measurement.
Branching ratio
−4
B(Λ0b → J/ψ pK − ) = (3.17 ± 0.04(stat) ± 0.07(syst) ± 0.34(Br)+0.45
−0.28 (fΛ0 /fd )) × 10
b
Translates into B for pentaquark states (with input from [PRL 115 (2015) 072001])
−5
B(Λ0b → Pc+ K − )B(Pc+ → J/ψ p) = (2.66 ± 0.22 ± 1.33+0.48
for Pc (4380)+
−0.38 ) × 10
−5
(1.30 ± 0.16 ± 0.35+0.23
for Pc (4450)+
−0.18 ) × 10
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
6/17
Properties of b-baryons
b-baryons other than Λ0b :
Weakly decaying: Ξb , Ωb
(∗)
Strongly decaying: Σb , Ξ0b , Ξ∗b , Ω∗b
Measurement of mass and lifetime statistically dominated, need modes with high
yields
Highest B for weak decays are either to
J/ψ and long-lived hyperon (cascade of long-lived particles, difficult to trigger and
reconstruct at LHCb)
Charmed baryon and π (with favoured c-baryon decay to hyperons again)
At LHCb, the highest yields are obtained with decays of c-baryons to
(Cabibbo-suppressed) multibody final states with protons:
−
+
− +
Ξ0b → Ξ+
c π , Ξc → pK π
0 −
0
− − +
Ξ−
b → Ξc π , Ξc → pK K π
0 −
0
− − +
Ω−
b → Ωc π , Ωc → pK K π
No long-lived decay products, no neutrals
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
7/17
Properties of Ξ∗0
b baryon
− +
Ξ∗0
b was discovered by CMS in Ξb π spectrum.
[PRL 108 (2012) 252002]
100
Full fit
−
Ξb → Ξ0cπ−
−
Ξb → Ξ0cρ−
−
−
Ξb → Ξ0cK
Combinatorial
LHCb
preliminary
50
Entries per 2 MeV/c2
Entries per 5 MeV/c2
− +
−
0 −
0
− − +
Ξ∗0
b → Ξb π , Ξb → Ξc π , Ξc → pK K π
[arXiv:1604.03896]
140
LHCb
120
preliminary
100
RS
80
WS
60
40
20
0
5600
5700
5800
5900
0
6000
50
100
150
200
δm [MeV/c2]
m(Ξ0cπ−) [MeV/ c2]
−
+
2
m(Ξ∗0
b ) − m(Ξb ) − m(π ) = 15.727 ± 0.068 ± 0.023 MeV/c
2
m(Ξ∗0
b ) = 5953.02 ± 0.07 ± 0.02 ± 0.55 MeV/c
Γ(Ξ∗0
b ) = 0.90 ± 0.16 ± 0.08 MeV
− +
∗0
σ(pp → Ξ∗0
b X ) B(Ξb → Ξb π )
= 0.27 ± 0.03 ± 0.01
−
σ(pp → Ξb X )
Anton Poluektov
Beauty hadron decays at LHCb
Large part of Ξ−
b comes from
excited states
Beauty 2016, Marseille, France, 1 – 6 May 2016
8/17
Properties of Ξ∗0
b baryon
− +
Ξ∗0
b was discovered by CMS in Ξb π spectrum.
[PRL 108 (2012) 252002]
100
Full fit
−
Ξb → Ξ0cπ−
−
Ξb → Ξ0cρ−
−
−
Ξb → Ξ0cK
Combinatorial
LHCb
preliminary
50
Entries per 0.45 MeV/c2
Entries per 5 MeV/c2
− +
−
0 −
0
− − +
Ξ∗0
b → Ξb π , Ξb → Ξc π , Ξc → pK K π
[arXiv:1604.03896]
60
LHCb
50
preliminary
40
30
20
10
0
5600
5700
5800
5900
0
6000
10
20
30
40
δm [MeV/c2]
m(Ξ0cπ−) [MeV/ c2]
−
+
2
m(Ξ∗0
b ) − m(Ξb ) − m(π ) = 15.727 ± 0.068 ± 0.023 MeV/c
2
m(Ξ∗0
b ) = 5953.02 ± 0.07 ± 0.02 ± 0.55 MeV/c
Γ(Ξ∗0
b ) = 0.90 ± 0.16 ± 0.08 MeV
− +
∗0
σ(pp → Ξ∗0
b X ) B(Ξb → Ξb π )
= 0.27 ± 0.03 ± 0.01
−
σ(pp → Ξb X )
Anton Poluektov
Beauty hadron decays at LHCb
Large part of Ξ−
b comes from
excited states
Beauty 2016, Marseille, France, 1 – 6 May 2016
8/17
Properties of Ω−
b baryon
Discovered at Tevatron, but mass discrepancy between CDF and D0
−
Mass and lifetime measured earlier by LHCb with Ω−
mode.
b → J/ψ Ω
−
HQE expects τ (Ξ0b ) ' τ (Λ0b ) ' 0.95[τ (Ω−
b ) ' τ (Ξb )] (e.g. [A. Lenz, arXiv:1405.3601])
300
Full fit
preliminary
Ξb→ Ξc π−
−
0
−
Ξb→
0
Ξc ρ−
Ξc comb.
0
200
−
−
Ξb→ Ξ0cK
−
Ξb comb.
Candidates / (20 MeV/c 2)
Candidates / (10 MeV/c 2)
[arXiv:1604.01412]
LHCb
LHCb
30
Full fit
−
Ωb→ Ω0cπ−
preliminary
−
Ωb→ Ωc ρ−
Ωc comb.
0
−
−
Ω0c → pK − K − π +
Ωb→ Ωc K
20
0
−
−
Ωb→ Ω*0
c π
−
Ωb comb.
10
100
0 −
Ω−
,
b → Ωc π
0
Measure mass and
lifetime wrt.
Ξ0b → Ξ0c π − ,
5800
6000
6200
5800
M(Ξ0cπ−) [MeV/ c 2]
LHCb
preliminary
6400
M(Ω0cπ−) [MeV/ c 2]
Ξ0c → pK − K − π +
−
−
τ (Ω−
b )/τ (Ξb ) = 1.11 ± 0.16 ± 0.03
0.05
5
10
decay time [ps]
Anton Poluektov
6200
2
m(Ω−
b ) = 6045.1 ± 3.2 ± 0.5 ± 0.6 MeV/c
0.1
0
0
6000
−
2
m(Ω−
b ) − m(Ξb ) = 247.4 ± 3.2 ± 0.5 MeV/c
0.15
−
N( Ωb ) / N( Ξb )
5600
Beauty hadron decays at LHCb
τ (Ω−
b ) = 1.78 ± 0.26 ± 0.05 ± 0.06 ps
Beauty 2016, Marseille, France, 1 – 6 May 2016
9/17
Λ0b → ψ(2S)pK − and Λ0b → J/ψ π + π − pK − decays
Measurement of decays to excited charmonium is important to evaluate QCD
factorisation-breaking effects.
Λ0b → ψ(2S)pK − with both ψ(2S) → µ+ µ− and J/ψ π + π −
Non-resonant
Λ0b
+
−
→ J/ψ pπ π K
−
[arXiv:1603.06961]
as well.
Candidates/(1 MeV/c2 )
Candidates/(2 MeV/c2 )
150
LHCb
preliminary
100
50
0
5.6
m(ψ(2S)[→ µ+ µ− ]pK − )
5.65
GeV/c2
LHCb
3000
2000
1000
0
preliminary
5.6
m(J/ψ pK − )
B(Λ0b → ψ(2S)pK − )
= (20.70 ± 0.76 ± 0.46 ± 0.37) × 10−2
B(Λ0b → J/ψ pK − )
Anton Poluektov
Beauty hadron decays at LHCb
5.65
GeV/c2
Beauty 2016, Marseille, France, 1 – 6 May 2016
10/17
Λ0b → ψ(2S)pK − and Λ0b → J/ψ π + π − pK − decays
Measurement of decays to excited charmonium is important to evaluate QCD
factorisation-breaking effects.
Λ0b → ψ(2S)pK − with both ψ(2S) → µ+ µ− and J/ψ π + π −
150
+
−
→ J/ψ pπ π K
−
[arXiv:1603.06961]
as well.
Candidates/(1 MeV/c2 )
Candidates/(2 MeV/c2 )
Non-resonant
Λ0b
LHCb
preliminary
100
50
LHCb
40
preliminary
20
0
0
5.6
m(J/ψ π + π − pK − )
5.65
GeV/c2
3.67
3.68
m(J/ψ π + π − )
B(Λ0b → ψ(2S)pK − )
= (20.70 ± 0.76 ± 0.46 ± 0.37) × 10−2
B(Λ0b → J/ψ pK − )
3.69
3.7
GeV/c2
B(Λ0b → J/ψ π + π − pK − )
= (20.86 ± 0.96 ± 1.34) × 10−2
B(Λ0b → J/ψ pK − )
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
10/17
Λ0b → ψ(2S)pK − and Λ0b → J/ψ π + π − pK − decays
Compare with other B(b → ψ(2S)X )/B(b → J/ψ X ) measurements [arXiv:1603.06961]
total unc.
stat. unc.
Λb→ψ pK
0
LHCb 2016
B(Bc+ → ψ(2S)π + )/B(Bc+ → J/ψ π)
[PRD 92 (2015) 072007]
LHCb 2015
B0s →ψ π+πBs0→ψ η'
LHCb 2013
LHCb 2012
D0 2009
CDF 2006
B0s →ψ φ
LHCb 2013
B →ψ π π
LHCb 2012
CDF 1998
B0→ψ K*0
LHCb 2012
B+→ψ π+
LHCb 2012
D0 2009
CDF 1998
B+→ψ K+
800
700
600
3 fb-1
400
300
200
50
40
Data
LHCb 7&8 TeV
Total fit
3 fb-1
Signal
30
Comb.bkg
Part.rec.bkg
20
10
100
0
0.4
6100
+ -
0.6
0.8
1
BR(b→ψ (2S)X)/BR(b→J/ ψ X)
difference for B, Bc and Λ0b :
significant
factorisation-breaking effects
Anton Poluektov
LHCb 7&8 TeV
500
0
0.2
Data
Total fit
Signal
Comb.bkg
Part.rec.bkg
B+c → J/ ψK+
Candidates / ( 5MeV/c2)
LHCb 2013
Candidates / ( 5MeV/c2)
B+c→ψ π+
LHCb 2015
LHCb 2013
B0s →ψ η
-
Beauty hadron decays at LHCb
B(Bc+
6200
6300
6400
6500
M(J/ψ π+) (MeV/c2)
0
6100
6200
6300
6400
6500
M(ψ(2S) π+) (MeV/c2)
+
→ ψ(2S)π )
= 0.268 ± 0.032(stat) ± 0.007(syst) ± 0.006(BF)
B(Bc+ → J/ψ π)
[See poster by Liupan An]
Low energy release allows for precise Λ0b mass
measurement (the most precise for any
b-hadron!):
M(Λ0b ) = 5619.65 ± 0.17 ± 0.17 MeV/c 2
Beauty 2016, Marseille, France, 1 – 6 May 2016
11/17
Search for the Λ0b → Λη and Λ0b → Λη 0 decays
Probe η − η 0 mixing, determine mixing angles φp (ss) and φg (gluonic):
|η 0 i = cos φg sin φp |ηq i + cos φg cos φp |ηs i + sin φg |gg i
Gluonic:
80
LHCb
Long K0s
Candidates / (29.7 MeV/c2 )
Candidates / (20.3 MeV/c2 )
Dominant:
Data
Fit0 Model
B → K 0s η'
Background
70
60
50
40
30
20
5000
5100
5200
5300
LHCb
Long Λ0
5400
LHCb
Long Λ0
Data
Fit0 Model
Λb→ Λ0η'
Background
12
10
5500
6
0
)
4
3.5
0
5600
Data
Fit0 Model
Λb→ Λ0η'
Background
4
3
2.5
2
1.5
3.5
3
5200
5400
5600
5800
6000
M(Λ0η') ( MeV/c2 )
LHCb
Long Λ0
Data
Fit0 Model
Λb→ Λ0η
Background
2.5
2
0.5
5400
Anton Poluektov
5600
5800
6000
M(Λ0η') ( MeV/c2 )
0
−6
B(Λ0b → Λη) = (9.3+7.3
−5.3 ) × 10
B(Λ0b → Λη 0 ) < 3.1 × 10−6
1
1
5200
3σ evidence of Λ0b → Λη :
Upper limit on B(Λ0b → Λη 0 ):
1.5
0.5
0
[JHEP 09 (2015) 006]
η → γγ, η 0 → π + π − η, π + π − γ
Control channel: B 0 → KS0 η (
8
M(K0sη') ( MeV/c2 )
Candidates / (20.3 MeV/c2 )
Candidates / (29.7 MeV/c2 )
4.5
14
2
10
0
16
5300
5400
5500
Beauty hadron decays at LHCb
5600
5700
5800
5900
M(Λ0η) ( MeV/ c2 )
Beauty 2016, Marseille, France, 1 – 6 May 2016
12/17
Search for the Λ0b → Λη and Λ0b → Λη 0 decays
Probe η − η 0 mixing, determine mixing angles φp (ss) and φg (gluonic):
|η 0 i = cos φg sin φp |ηq i + cos φg cos φp |ηs i + sin φg |gg i
Gluonic:
90
LHCb
0
Downstream Ks
Candidates / (29.7 MeV/c2 )
Candidates / (20.3 MeV/c2 )
Dominant:
Data
Fit0 Model
B → K 0s η'
Background
80
70
60
50
40
30
7
LHCb
Downstream Λ0
Data
Fit0 Model
Λb→ Λ0η'
Background
6
5
4
[JHEP 09 (2015) 006]
η → γγ, η 0 → π + π − η, π + π − γ
Control channel: B 0 → KS0 η (
3
0
)
2
20
1
10
2
1.8
5000
5100
5200
5300
LHCb
Downstream Λ0
5400
5500
Data
Fit0 Model
Λb→ Λ0η'
Background
1.6
0
5600
M(K0sη') ( MeV/c2 )
1.4
1.2
1
0.8
0.6
Candidates / (20.3 MeV/c2 )
Candidates / (29.7 MeV/c2 )
0
3.5
3
5200
5400
5600
5800
6000
M(Λ0η') ( MeV/c2 )
LHCb
Downstream Λ0
Data
Fit0 Model
Λb→ Λ0η
Background
2.5
2
3σ evidence of Λ0b → Λη :
−6
B(Λ0b → Λη) = (9.3+7.3
−5.3 ) × 10
Upper limit on B(Λ0b → Λη 0 ):
1.5
B(Λ0b → Λη 0 ) < 3.1 × 10−6
1
0.4
0.5
0.2
0
5200
5400
Anton Poluektov
5600
5800
6000
M(Λ0η') ( MeV/c2 )
0
5300
5400
5500
Beauty hadron decays at LHCb
5600
5700
5800
5900
M(Λ0η) ( MeV/ c2 )
Beauty 2016, Marseille, France, 1 – 6 May 2016
12/17
0 −
Evidence for the strangeness-changing decay Ξ−
b → Λb π
Typically, lifetime of b-hadrons is determined by b decay.
In hadrons containing strange quark, its weak decay should contribute ∼ 1%.
Enhanced up to 8% in some models [M. Shifman, A. Vainshtein, PRD 71 (2005) 074010]
No such decays have been observed before.
[PRL 115 (2015) 241801]
Candidates / (5 MeV/c 2)
0 −
0
+ −
+
− +
decay chain
Use Ξ−
b → Λb π , Λb → Λc π , Λc → pK π
30000
Full fit
LHCb
Λb→ Λc π−
0
+
Λ0b→ Λ+cρ−
Λ0b→
20000
−
Λ+cK
Combinatorial
Data
10000
0
5400
5500
5600
5700
5800
Λ+cπ− mass [MeV/c 2]
Λ0b is not produced in the PV, but almost points to it because of small Q
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
13/17
0 −
Evidence for the strangeness-changing decay Ξ−
b → Λb π
Full fit
LHCb
−
Ξb→ Λ0bπ−
150
(*)−
Σb →
Λ0bπ−
Combinatorial
Data
100
Candidates / (4 MeV/c 2)
Candidates / (4 MeV/c 2)
[PRL 115 (2015) 241801]
50
100
b
150
Combinatorial
Data
100
50
M(Λ0bπ−)-M(Λ0b)-M(π−) [MeV/c 2]
fΛ0
(*)+
Σb → Λ0bπ+
50
50
f Ξ−
LHCb
Full fit
100
M(Λ0bπ+)-M(Λ0b)-M(π+) [MeV/c 2]
0 −
+0.8
−4
B(Ξ−
b → Λb π ) = (5.7 ± 1.8−0.9 ) × 10
3.2σ significance
b
Assuming 0.1 <
f −
Ξ
b
fΛ0
0 −
< 0.3, B(Ξ−
b → Λb π ) is in range (0.19 − 0.76)%
b
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
14/17
Bc+ and its production
1.8
1.6
LHCb data
1.4
BCVEGPY
R(y ) (%)
T
R(p ) (%)
The only doubly heavy state known so far.
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
15
20
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
2
LHCb data
BCVEGPY
2.5
3
3.5
4
p (GeV/c)
4.5
y
T
Production is suppressed in pp collisions:
fc B(Bc+ → J/ψ π + )
R=
= (0.683 ± 0.018 ± 0.009)%
fu B(B + → J/ψ K + )
[PRL 114 (2015) 132001]
Unique laboratory to study QCD effects:
Decays into charmonia are colour-favoured (light b mesons: colour-suppressed).
Test factorisation.
Decays into charmless final states are of purely annihilation topology
(light b mesons: interference of annihilation (exchange) and penguin).
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
15/17
Search for Bc+ → ppπ +
Candidates/(0.01 GeV/c 2)
[arXiv:1603.07037]
Candidates/(0.01 GeV/c2 )
LHCb
40
preliminary
30
b
u
20
p
Vud
Bc−
10
0
6
6.1
6.2
6.3
6.4
6.5
m(ppπ) (GeV/c 2 )
∗
Vub
c̄
p
d
π−
10
LHCb
preliminary
8
6
Control sample: B + → ppπ +
4
2
0
Candidates/(0.01 GeV/c2 )
Search for purely annihilation-type decay:
50
6
6.1
6.2
6.3
6.4
6.5
m(ppπ) (GeV/c 2 )
7
LHCb
6
m(pp) < 2.85 MeV/c 2
fc
B(Bc+ → ppπ + ) < 3.6 × 10−8
fu
preliminary
5
4
3
2
1
0
6
Anton Poluektov
6.1
6.2
6.3
6.4
6.5
m(ppπ) (GeV/c 2 )
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
16/17
Search for Bc+ → ppπ +
Candidates/(0.01 GeV/c 2)
[arXiv:1603.07037]
25
Candidates/(0.01 GeV/c2 )
LHCb
20
preliminary
15
b
u
10
p
Vud
5
0
Bc−
6
6.1
6.2
6.3
6.4
6.5
m(ppπ) (GeV/c 2 )
∗
Vub
c̄
p
d
π−
7
LHCb
6
preliminary
5
4
3
Control sample: B + → ppπ +
2
1
0
Candidates/(0.01 GeV/c2 )
Search for purely annihilation-type decay:
6
6.1
6.2
3
6.3
6.4
6.5
m(ppπ) (GeV/c 2 )
LHCb
preliminary
2.5
2
1.5
1
0.5
0
m(pp) < 2.85 MeV/c 2
fc
B(Bc+ → ppπ + ) < 3.6 × 10−8
fu
6
Anton Poluektov
6.1
6.2
6.3
6.4
6.5
m(ppπ) (GeV/c 2 )
Beauty hadron decays at LHCb
Charmonium region:
2.85 < m(pp) < 3.15 MeV/c 2
fc
B(Bc+ → J/ψ (→ pp)π + ) < 8.4 × 10−8
fu
Beauty 2016, Marseille, France, 1 – 6 May 2016
16/17
Summary
Beauty baryons and Bc+ have been a mostly unexplored
territory before LHC
Interesting from the point of view of theory
NP in rare decays
CP violation and precision UT measurements
Probing QCD in the different regime than light
b-mesons
LHCb has a great potential:
b-baryon production and spectroscopy
b-baryon decays (including fully-hadronic, semileptonic
and with neutrals in final state)
Bc+ decays (mostly with charmonium, but starting
investigation of fully hadronic final states)
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
17/17
LHCb
One-arm spectrometer optimised for studies of beauty and charm decays
Angular acceptance
η
2
2<η<5
8
LHCb acceptance
6
GPD acceptance
4
2
0
-2
-4
LHCb MC
s = 14 TeV
-6
-8
-8
-6
-4
-2
0
2
4
6
8
η
1
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
18/17
LHCb
One-arm spectrometer optimised for studies of beauty and charm decays
Vertexing
Bs0 oscillations with Bs0 → Ds π
[New J. Phys. 15 (2013) 053021]
Good vertexing: measure B 0 and Bs0 oscillations, reject prompt background
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
18/17
LHCb
One-arm spectrometer optimised for studies of beauty and charm decays
PID
K /π ID efficiency and misID rate
[EPJ C73 (2013) 2431]
Good vertexing: measure B 0 and Bs0 oscillations, reject prompt background
Particle identification: flavour tagging, misID background
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
18/17
LHCb
One-arm spectrometer optimised for studies of beauty and charm decays
Tracking
µ+ µ− mass spectrum
[PRL 111 (2013) 101805]
Good vertexing: measure B 0 and Bs0 oscillations, reject prompt background
Particle identification: flavour tagging, misID background
High-resolution tracking
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
18/17
LHCb
One-arm spectrometer optimised for studies of beauty and charm decays
Calorimetry
Bs0 → χc1 φ, χc1 → J/ψγ
[Nucl. Phys. B874 (2013) 663]
Good vertexing: measure B 0 and Bs0 oscillations, reject prompt background
Particle identification: flavour tagging, misID background
High-resolution tracking
Calorimetry: reconstruct neutrals (π 0 , γ) in the final state
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
18/17
LHCb
One-arm spectrometer optimised for studies of beauty and charm decays
Calorimetry
Bs0 → χc1 φ, χc1 → J/ψγ
[Nucl. Phys. B874 (2013) 663]
Good vertexing: measure B 0 and Bs0 oscillations, reject prompt background
Particle identification: flavour tagging, misID background
High-resolution tracking
Calorimetry: reconstruct neutrals (π 0 , γ) in the final state
Efficient trigger, including fully hadronic modes
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
18/17
LHCb in Run 1 and Run 2
3 fb−1 in 2011 and 2012
Anton Poluektov
Beauty hadron decays at LHCb
320 pb−1 in 2015
Beauty 2016, Marseille, France, 1 – 6 May 2016
19/17
LHCb trigger
Significant changes introduced this year in the LHCb trigger:
2011 and early 2012: increased trigger bandwidth
(compared to design 2 kHz) to accommodate
charm
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
20/17
LHCb trigger
Significant changes introduced this year in the LHCb trigger:
2011 and early 2012: increased trigger bandwidth
(compared to design 2 kHz) to accommodate
charm
2012: deferred trigger configuration: keep the
trigger farm busy between fills
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
20/17
LHCb trigger
Significant changes introduced this year in the LHCb trigger:
2011 and early 2012: increased trigger bandwidth
(compared to design 2 kHz) to accommodate
charm
2012: deferred trigger configuration: keep the
trigger farm busy between fills
2015: split trigger
All 1st stage (HLT1) output stored on disk
Used for real-time calibration and alignment
2nd stage (HLT2) uses offline-quality calibration
5 kHz of 12 kHz to Turbo stream:
Candidates produced by trigger are stored
No raw event ⇒ smaller event size
Used for high-yield channels (charm, J/ψ , . . .)
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
20/17
Production of Λ0b and B(Λ0b → J/ψ pK − )
[Chin. Ph. C 40 (2016) 011001]
0
0.2
ap+d
ap+d
Asymmetry between Λ0b and Λb (sum of production and decay, ap+d ):
0
N(Λ0b ) − N(Λb )
ap+d =
0
N(Λ0b ) + N(Λb )
LHCb
0.2
0.1
0.1
0
0
−0.1
−0.2
0
5
10
7 TeV fit
7 TeV data
8 TeV fit
8 TeV data
15
20
p [GeV/c]
LHCb
−0.1
−0.2
2
2.5
3
7 TeV fit
7 TeV data
8 TeV fit
8 TeV data
3.5
T
4
4.5
y
Asymmetry as function of pT consistent with constant
Significant slope as function of rapidity:
ap+d (y ) = (−0.001 ± 0.007) + (0.058 ± 0.014)(y − 3.1)
Λ0b fraction increases with rapidity. “Baryon number transport” mechanism
from beam to Λ0b
[J. Rosner, PRD 90 (2014) 014023]
Anton Poluektov
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
21/17
Measurement of |Vub | in Λ0b → pµν
[LHCb, Nature Phys. 11 (2015) 743]
Use Λ0b sample for |Vub | measurement, cleaner final
state
Measure |Vub |/|Vcb | from
|Vub /Vcb |2 =
B(Λ0b →pµν)
RFF
B(Λ0b →Λ+
c µν)
Fit corrected mass Mcorr =
p
2
pT2 + Mpµ
+ pT
4000
Candidates / (50 MeV/c2)
Candidates / (40 MeV/c2)
|Vub | = [3.27 ± 0.15 ± 0.16(LQCD) ± 0.06(Vcb )] × 10−3
LHCb
Λ c+µ − ν
−
Λ *+
c µ ν
Combinatorial
3000
2000
1000
0
4000
4500
−
5000
5500
Corrected pK π +µ − mass [MeV/c2]
Anton Poluektov
18000
15000
12000
9000
Combinatorial
Mis-identified
D0 p µ − ν
Λ*c+µ − ν
Λ +c µ − ν
N *µ − ν
p µ −ν
LHCb
6000
3000
0
3000
Beauty hadron decays at LHCb
4000
5000
Corrected p µ − mass [MeV/c2]
Beauty 2016, Marseille, France, 1 – 6 May 2016
22/17
Λ0b and Ξ0b decays to Λh+ h0−
Large CP-violation is observed in charmless 3-body B decays
No CP-violation has yet been seen in decays of baryons
No charmless Ξb decays has been seen.
200
180
160
140
120
100
80
60
40
20
0
LHCb
preliminary
5400
5600
5800
Candidates / ( 20 MeV/c2 )
Candidates / ( 20 MeV/c2 )
−
+
+
Λ0b , Ξ0b → Λh+ h0− ; control mode: Λ0b → Λ+
c π , Λc → Λπ
B(Λ0b → ΛK + π − ) = (5.6 ± 0.8 ± 0.8 ± 0.7) × 10−6
60
40
B(Λ0b → ΛK + K − ) = (15.9 ± 1.2 ± 1.2 ± 2.0) × 10−6
20
5400
5600
LHCb
50
preliminary
40
30
20
10
0
5800
6000
m(Λπ +π −) [MeV/c2]
Candidates / ( 20 MeV/c2 )
Candidates / ( 20 MeV/c2 )
m(Λπ +π −) [MeV/c2]
60
B(Λ0b → Λπ + π − ) = (4.6 ± 1.2 ± 1.4 ± 0.6) × 10−6
preliminary
80
0
6000
LHCb
100
[arXiv:1603.00413]
B(Ξ0b → Λπ + π − ) < 1.7 × 10−6
90
B(Ξ0b → ΛK + π − ) < 0.8 × 10−6
LHCb
80
preliminary
70
60
B(Ξ0b
50
+
→ ΛK K
−
(CL=90%)
−6
) < 0.3 × 10
40
30
ACP (Λ0b → ΛK + π − ) = −0.53 ± 0.23 ± 0.11
20
10
5400
5600
5800
6000
0
5400
5600
m(ΛK ± π ) [MeV/c2]
±
Anton Poluektov
Beauty hadron decays at LHCb
5800
−
6000
m(ΛK +K ) [MeV/c2]
ACP (Λ0b → ΛK + K − ) = −0.28 ± 0.10 ± 0.07
Beauty 2016, Marseille, France, 1 – 6 May 2016
23/17
B(Bc+ → ψ(2S)π + )/B(Bc+ → J/ψ π)
As with Λ0b decays, probe QCD factorisation by measuring the ψ(2S)/J/ψ ratio.
800
700
600
Data
Total fit
Signal
Comb.bkg
Part.rec.bkg
B+c → J/ ψK+
LHCb 7&8 TeV
-1
3 fb
500
400
300
200
Candidates / ( 5MeV/c2)
Candidates / ( 5MeV/c2)
[PRD 92 (2015) 072007]
50
40
Data
LHCb 7&8 TeV
Total fit
-1
3 fb
Signal
30
Comb.bkg
Part.rec.bkg
20
10
100
0
6100
B(Bc+ →ψ(2S)π + )
B(Bc+ →J/ψ π)
Anton Poluektov
6200
6300
6400
6500
M(J/ψ π+) (MeV/c2)
0
6100
6200
6300
6400
6500
M(ψ(2S) π+) (MeV/c2)
= 0.268 ± 0.032(stat) ± 0.007(syst) ± 0.006(BF)
Beauty hadron decays at LHCb
Beauty 2016, Marseille, France, 1 – 6 May 2016
24/17