Precision measurement of B0 meson oscillation frequencyPrecision measurement of B0 meson oscillation...
Transcript of Precision measurement of B0 meson oscillation frequencyPrecision measurement of B0 meson oscillation...
Precision measurement of B0 meson oscillation frequency
Basem KhanjiOn behalf of the LHCb collaboration
Milano-Bicocca, INFN, CERN
22-March-2016
LHC Seminar, 22 March 2016
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 1 / 40
CKM matrix
LW ±int = − g√
2(uL, cL, tL)γµVCKM
dL
sL
bL
W+ + h.c
VCKM =
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
b c
W −
Vcb
• |Vij |2: probability of transition from one flavour to another
• Physics states 6= flavour states
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 2 / 40
CKM matrix
VCKM =
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
• Strength of the transition between up-type and down-type quarks
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 3 / 40
CP violation
• VCKM is complex & unitary
• Can be parametrized using 4 parameters: 3 real + 1 complex
VCKM ∼
1− λ2/2 λ Aλ3(ρ− iη)
−λ 1− λ2/2 Aλ2
Aλ3(1− ρ− iη) −Aλ2 1
6= V ∗CKM
• Nature discriminates(!) between matter and anti-matter
• η is small → where did the anti-matter go?
• Test the consistency of CKM picture within SM experimentally
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 4 / 40
Unitarity Triangle
VudV ∗ub + VcdV ∗
cb + VtdV ∗tb = 0
• One example of unitarity triangles
• There are six more
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 5 / 40
Unitarity Triangle
VudV ∗ub + VcdV ∗
cb + VtdV ∗tb = 0
γ
α
α
dm∆ Kε
sm∆ & dm∆
ubV
βsin 2(excl. at CL > 0.95)
< 0βsol. w/ cos 2
α
βγ
ρ
0.4 0.2 0.0 0.2 0.4 0.6 0.8 1.0
η
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
exclu
ded
are
a h
as C
L >
0.9
5EPS 15
CKMf i t t e r
• On the other hand: sides + angles are related to physics observables
• ... most of them are accessible through b-hadron decays
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 6 / 40
How to fish for b-hadrons
• 25% of bb pairs are produced forward
0/4π
/2π/4π3
π
0
/4π
/2π
/4π3
π [rad]1θ
[rad]2θ
1θ
2θ
b
b
z
LHCb MC = 7 TeVs
• → LHCb: forward spectrometer with unique η coverage (2 < η < 5)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 7 / 40
LHCb detector
Int. J. Mod. Phys. A 30 (2015) 1530022• VELO : σ(IP) ∼ 20µm for high pT tracks• Tracking system : δ(p)/p = (0.5− 1)%, reversible magnet polarity• RICH system : ε(K) ∼ 95%, 5% π → K mis-id probability• Calorimeter : Energy measurement, identify π0,γ• Muon detector : ε(µ)∼ 97%, (1− 3)%, π → µ mis-id probability
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 8 / 40
Luminosity
Run I(2011 + 2012): 3 fb−1 Run II (2015): 300 pb−1
• + increase in bb cross section (7TeV→ 13 TeV)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 9 / 40
A precise measurement of the B0 meson oscillation frequency,LHCB-PAPER-2015-031 1
1Paper is in preparationB. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 10 / 40
Theory
• Flavour oscillation(mixing) through electroweak interaction in neutral B mesons
�B0 B0
W−
u, c, t
W+
u, c, t
d b
b d
�B0 B0
u, c, t
W± W±
u, c, t
d b
b d
• Physics states |BH,L〉 = p|B0〉 ∓ q|B0〉 (p2 + q2 = 1)
• Mass difference between the two physics states: ∆md = mH −mL
• Flavour at production is the flavour of the state at t = 0
• Flavour at decay the flavour of the state at decay time t
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 11 / 40
Theory
• Box diagram calculation leads to:
∆md =G2Fm2
WMB0
6π2 S0(xt)η2B|V ∗tdVtb|2f 2
B0 BB0
• → ∆md constrains the side of theunitarity triangle
• But needs theory input
• B0-B0 system is described by Schrödinger equation
i ddt
(|B0(t)〉|B0(t)〉
)=(
M̂d − i2 Γ̂d)( |B0(t)〉
|B0(t)〉
)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 12 / 40
Theory
• Mixing probability for neutral B0 mesons:
P(t) ∝ e−tτ (1 + qmixing cos(∆md t))
• Unmixed events: qmixing = 1flavour at production = flavour atdecay
• Mixed events: qmixing = −1flavour at production 6= flavour atdecay
0 1 2 3 4
Inte
nsity
0
0.5
1
y = 0.997x = -0.946: 0K(a)
0 1 2 3 4
-610
-410
-210
1
y = 0.0075x = 0.0063: 0D(b)
tΓ0 1 2 3 4
Inte
nsity
0
0.5
1
y = 0.005x = 0.773: 0B(c)
tΓ0 1 2 3 40
0.5
1
y = 0.046x = 25.194: sB(d)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 13 / 40
State of the art
0.4 0.45 0.5 0.55
∆md (ps
-1)
World averagefor PDG 2015
0.510 ± 0.003 ps-1
CLEO+ARGUS(χ
d measurements)
0.498 ± 0.032 ps-1
Average of aboveafter adjustments
0.510 ± 0.003 ps-1
LHCb *
(3 analyses) 0.514 ± 0.005 ± 0.003 ps
-1
BELLE *
(3 analyses) 0.509 ± 0.004 ± 0.005 ps
-1
BABAR *
(4 analyses) 0.506 ± 0.006 ± 0.004 ps
-1
D0 (1 analysis)
0.506 ± 0.020 ± 0.016 ps-1
CDF1 *
(4 analyses) 0.495 ± 0.033 ± 0.027 ps
-1
OPAL (5 analyses)
0.479 ± 0.018 ± 0.015 ps-1
L3 (3 analyses)
0.444 ± 0.028 ± 0.028 ps-1
DELPHI *
(5 analyses) 0.519 ± 0.018 ± 0.011 ps
-1
ALEPH (3 analyses)
0.446 ± 0.026 ± 0.019 ps-1
* HFAG average
without adjustments
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 14 / 40
Main components
• Need: "flavour specific" decays with high yields• B0→ D−µ+νµ (D−→ K+π−π−): ∼ 1.6M events (full Run I data: 3 fb−1)• B0→ D∗−µ+νµ (D∗− → D0(→ K+π−)π−): ∼ 0.8M events (full Run I data: 3 fb−1)• µ charge is correlated with B0 flavour at decay
• Need: Flavour Tagging (qmixing)
• Need: Decay time reconstruction (t)
B0 → D−µ+νµ B0 → D∗−µ+νµ
B0
D-
π-
K+
μ+
υμ
π-
B0
D*-
D0
π-
K+
μ+
υμ
π-
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 15 / 40
Background: combinatorics
• First type of backgrounds: Combinatorics, D0 from B decays• Not sharing D(∗)− with the signal in their final state
• Apply sPlot technique to subtract those backgrounds (Nucl. Instrum. Meth. A555 (2005) 356)
• B0→ D∗−µ+νµ: mD0 , δm(= mD∗− −mD0 ) distributions• B0→ D−µ+νµ: mD− distribution
]2c [MeV/π πK m1800 1850 1900
)2 cE
vent
s /
( 1.
4 M
eV/
50
100
310× Data Total fit Signal Comb.
LHCb
]2c [MeV/mδ140 145 150 155
)2 cE
vent
s /
( 0.
125
MeV
/
10
20
30
40
310×
LHCb Data Total fit
*- D0 D
Comb.
LHCB-PAPER-2015-031 (preliminary)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 16 / 40
Background: B+ background
• B+→ D(∗)−µ+π+νµX decays: share same characteristics of signal but do not exhibitany oscillation
• Fraction of these B+→ D(∗)−µ+π+νµX decays correlated with ∆md• Need to fix it from somewhere
• B of B+→ D(∗)−µ+π+νµX has 10% uncertainty → could amplify systematic effect
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 17 / 40
Closer look at B+ background
• B+→ D∗−µ+π+νµX(Left), B0→ D∗−µ+νµ(Right)
PV
B+D*-
D~0K+
pi-
pi-
mu+
pi+
nu
PV
B0D*-
D~0K+
pi-
pi-
mu+
nu
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 18 / 40
B+ background: Isolation variables
• Conduct a search over all tracks to find if at least one of them originates from yourB candidate
• If your candidate is signal you will find nothing• If your candidate is background you will find one
PV
B+D*-
D~0K+
pi-
pi-
mu+
pi+
nu
PV
B0D*-
D~0K+
pi-
pi-
mu+
nu
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 19 / 40
B+ background: busted!
iso(D)-0.5 0 0.5 1
Ent
ries
(arb
. uni
ts)
Signal
Background
iso(all)-0.5 0 0.5 1
LHCb
iso(B)-0.5 0 0.5 1
iso(sum)-3 -2 -1 0
Ent
ries
(arb
. uni
ts)
]2c [MeV/corrm4000 6000 8000 10000
) [mm]D, πIP(5 10
LHCB-PAPER-2015-031 (preliminary)
• Merge these quantities into one MVA classifier to maximize the separationB. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 20 / 40
B+ background
• Apply a cut on the MVA classifier → reduce B+→ D(∗)−µ+π+νµX by ∼ 70%
-1 -0.5 0 0.5 1
Even
ts /
0.05
5
10
310×
LHCb (e)
-1 -0.5 0 0.5 10
5
10
15
20
310×
DataTotal fit
signal0B bkg.+B
(g)-1 -0.5 0 0.5 1
Even
ts /
0.05
5
10
310×
(f)
BDT output-1 -0.5 0 0.5 1
0
5
10
15
20
310×
(h)
3 10×
LHCB-PAPER-2015-031 (preliminary)
• Bonus: use the MVA output to estimate the contribution of B+→ D(∗)−µ+π+νµX• → avoid large uncertainty(∼ 10%) from B of B+→ D(∗)−µ+π+νµX in PDG
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 21 / 40
Flavour tagging: qmixing
• Mixing state qmixing: flavour at decay × flavour at production = ±1• Flavour at decay in B0→ D(∗)−µ+νµ is determined by µ charge• Flavour at production?
3/20 Ulrich Eitschberger | Updates on Flavour Tagging | 72nd LHCb week | June 19th, 2014
Flavour Tagging: Determine B production flavours SS Pion SS Kaon Signal Decay
Same Side
Opposite Side
OS Vertex Charge OS Muon OS Electron
OS Kaon
PV
• Flavour at production (qprod : ±1, 0), Tagging efficiency (ε): how often we tag andMistag probability (ω): how often we make a mistake
• Tagging Power = ε× (1− 2ω)2
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 22 / 40
Flavour tagging: qmixing
• Lepton taggers are clean but rare
• Cascade and vertex taggers are abundant but less pure
ω
Eur. Phys. J. C72 (2012) 2022
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 23 / 40
Flavour tagging: qmixing
[%]2)ω (1-2∈0 1 2 3 4 5 6 7 8
)d
m∆(
σ
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
• Sensitivity scales with 1/√ε× (1− 2ω)2
• Higher tagging power is equivalent to higher luminosityB. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 24 / 40
Flavour tagging: qmixing
• Mixing state qmixing: flavour at decay × flavour at production = ±1
N±(t) ∝ e−tτ (1 + qmixing(1− 2ω) cos(∆md t))
• Events are Grouped in 4 categories in increasing mistag probability• This increase the tagging power → increases sensitivity to ∆md• Tagging power for B0→ D(∗)−µ+νµ ∼ 2.5%
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 25 / 40
Determination of B0 decay time: Problem
t =LB0 MB0
pB0
• Missing neutrino → pB0 cannot be known in data (only in simulation)• Decay time accessible in data is:
tdata =LB0 MB0
pDµ
B0 → D−µ+νµ B0 → D∗−µ+νµ
B0
D-
π-
K+
μ+
υμ
π-
B0
D*-
D0
π-
K+
μ+
υμ
π-
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 26 / 40
Determination of B0 decay time: Solution
• To correct the decay time in data per event:• Get correction (k) from simulation:
k =pDµ
pB0
• Improve the correction of the momentum: k-factor as a function of visible mass
tcorrected = tdata × k(MDµ)
]2c mass [MeV/µD*B3500 4000 4500 5000
-facto
rk
0.30.40.50.60.70.80.9
11.11.2 )2 c
Even
ts/(0
.004
)/(11
MeV
/
0
5
10
15
20
25
30
35LHCb
LHCB-PAPER-2015-031 (preliminary)B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 27 / 40
Determination of B0 decay time: Resolution
• Detector resolution on the flight distance of the B0 (R(L))
• k → k(mDµ) → additional resolution function (F (k))
• Momentum resolution introduces the largest effect in time resolution
N±(t) ∝ e−tτ (1 + qmixing(1− 2ω) cos(∆md t))⊗ R(L)⊗ F (k)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 28 / 40
Tagged time-dependent fit
• Use binned likelihood sFit (arXiv:0905.0724) to extract ∆md
P(t, qmixing) = (1− fB+ )S(t, qmixing) + fB+B+(t, qmixing)
• S(t, q),B+(t, q): decay rates of signal & background• fB+ : fraction of the B+→ D(∗)−µ+π+νµX in the sample
t [ps]5 10 15
Even
ts / (
0.14
7 ps
)
0
10
20
30
40
50
310×
DataTotal fit
signal0B bkg.+B
LHCb
t [ps]5 10 15
Even
ts / (
0.14
7 ps
)
0
5
10
15
20
25
30
35310×
DataTotal fit
signal0B bkg.+B
LHCb
B0 → D−µ+νµ B0 → D∗−µ+νµ
LHCB-PAPER-2015-031 (preliminary)B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 29 / 40
Time dependent asymmetries
5 10
-0.5
0
0.5 LHCb
(a)
5 10
-0.5
0
0.5
(c)
5 10
-0.5
0
0.5
(b)
5 10
-0.5
0
0.5
(d)
)t(A
[ps]t
5 10
-0.5
0
0.5 LHCb
(e)
5 10
-0.5
0
0.5
(g)
5 10
-0.5
0
0.5
(f)
5 10
-0.5
0
0.5
(h)
)t(A
[ps]t
B0 → D−µ+νµ B0 → D∗−µ+νµ
LHCB-PAPER-2015-031 (preliminary)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 30 / 40
Systematic uncertainties
• Several sources of systematic uncertainties• k-factor method, B+ and other background sources & Other sources (time acceptance,
detector resolution, momentum and length scale)
• Large number of parameterized simulation to evaluate systematic uncertainties
Source of uncertaintyB0→ D−µ+νµ [ns−1] B0→ D∗−µ+νµ [ns−1]
Uncorrelated Correlated Uncorrelated CorrelatedB+ background 0.4 0.1 0.4 –Other backgrounds – 0.5 – –k-factor distribution 0.4 0.5 0.3 0.6Other fit-related 0.5 0.4 0.3 0.5Total 0.8 0.8 0.6 0.8
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 31 / 40
... and ∆md is
• Fits performed separately for per channel and per year
• Combination across the two channel using weighted average
• Results per decay channel (LHCB-PAPER-2015-031):
Mode 2011 sample 2012 sample Total sample∆md [ ns−1] ∆md [ns−1] ∆md [ns−1]
B0→ D−µ+νµ 506.2± 5.1stat 505.2± 3.1stat 505.5± 2.7stat ± 1.1syst
B0→ D∗−µ+νµ 497.5± 6.1stat 508.3± 4.0stat 504.4± 3.4stat ± 1.0syst
• Combination of ∆md measurement across the two channels using Run I data:
∆md = 505.0± 2.1 (stat)± 1.0 (syst) ns−1(preliminary)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 32 / 40
Theory catching up
∆md =G2Fm2
WMB0
6π2 S0(xt)η2B|V ∗tdVtb|2f 2
B0 BB0
• arXiv:1602.03560: Fermilab Lattice and MILC Collaborations
• Improvements on uncertainties related to hadronic matrix elements:
f 2B0 BB0 = 0.0526± 0.0042GeV/c2
∆md (Theory) = 0.639(50)(36)(5)(13) ps−1
∆md/∆ms(Theory) = 0.0323(9)(9)(0)(3)
• PDG 2015: ∆md = (0.510± 0.003) ps−1, ∆ms = (17.757± 0.021) ps−1
• Theory prediction for:∆md , ∆md/∆ms are 2.1, 2.9σ away from experiment
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 33 / 40
Conclusion
• LHCb measure ∆md inB0→ D(∗)−µ+νµ channels using 3 fb−1
∆md = 505.0± 2.1 (stat)± 1.0 (syst) ns−1
(preliminary)
• LHCb provides the most precisemeasurement of ∆md
• Better than the world average:(510± 3) ns−1(PDG 2015)
• Recent development from the lattice:∆md prediction is 2.1σ away fromworld average
]-1 [nsdm∆450 500 550
ALEPH (3 analyses) 19± 6 ±446
DELPHI (5 analyses) 11± 18 ±519
L3 (3 analyses) 28± 28 ±444
OPAL (5 analyses) 15± 18 ±479
CDF1 (4 analyses) 27± 33 ±495
D0 (1 analysis) 16± 20 ±506
BABAR (4 analyses) 4± 6 ±506
BELLE (3 analyses) 5± 4 ±509
LHCb (3 analyses) 3± 5 ±514
<0.66) +BABAR (P 0.25 + 0.26 - 0.25±4.15
This measurement 1.0± 2.1 ±505.0
BABAR (p*>1.3GeV) 0.27 + 0.19 - 0.21±4.32
Average (w/o this meas.) 3±510
HFAGSummer 2014
Bosch, Lange, Neubert and Paz (BLNP)Phys.Rev.D72:073006,2005
/dof = 9.2/11 (CL = 61.00 %)2χ
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 34 / 40
Backups
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 35 / 40
Time projections in 2012 data
t [ps]5 10 15
Eve
nts
/ (0.
147
ps)
0
10
20
30
40
50
310×
DataTotal fit
signal0B bkg.+B
LHCb
t [ps]5 10 15
Eve
nts
/ (0.
147
ps)
0
5
10
15
20
25
30
35310×
DataTotal fit
signal0B bkg.+B
LHCb
LHCB-PAPER-2015-031 (preliminary)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 36 / 40
D0 mass distributions for 2012
]2c [MeV/πK m1840 1860 1880 1900
)2 cE
vent
s / (
0.8
MeV
/
0
2
4
6
8
10
310×
LHCb Data Total fit
*- D0 D
Comb.
]2c [MeV/πK m1840 1860 1880 1900
)2 cE
vent
s / (
0.8
MeV
/
0
5
10
15
20
25
310×
LHCb Data Total fit
*- D0 D
Comb.
LHCB-PAPER-2015-031 (preliminary)
• D0 mass fits in B0→ D∗−µ+νµ decay
• Components with D∗−D0π can be only distinguished using δm(= mD∗− −mD0 )
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 37 / 40
Asymmetries in 2011
5 10
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(a)
5 10
-0.5
0
0.5
(c)
5 10
-0.5
0
0.5
(b)
5 10
-0.5
0
0.5
(d)
)t(A
[ps]t
5 10
-0.5
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(a)
5 10
-0.5
0
0.5
(c)
5 10
-0.5
0
0.5
(b)
5 10
-0.5
0
0.5
(d)
)t(A
[ps]t
LHCB-PAPER-2015-031 (preliminary)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 38 / 40
MVA classifier
-1 -0.5 0 0.5 1
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ts /
0.0
33
5
10
15
20
310×
LHCb (a)
-1 -0.5 0 0.5 10
50
100
310×
DataTotal fit
signal0B bkg.+B
(c)-1 -0.5 0 0.5 1
Even
ts /
0.0
33
5
10
15
20
310×
(b)
BDT output-1 -0.5 0 0.5 1
0
50
100
310×
(d)
3 10×
-1 -0.5 0 0.5 1
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ts /
0.0
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310×
LHCb (e)
-1 -0.5 0 0.5 10
5
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DataTotal fit
signal0B bkg.+B
(g)-1 -0.5 0 0.5 1
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ts /
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5
5
10
310×
(f)
BDT output-1 -0.5 0 0.5 1
0
5
10
15
20
310×
(h)
3 10×
B0→ D−µ+νµ B0→ D∗−µ+νµ
LHCB-PAPER-2015-031 (preliminary)
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 39 / 40
0.35 0.4 0.45 0.5 0.55 0.6 0.65
∆md (ps
-1)
World averageSummer 2015
0.5055 ±0.0020 ps-1
CLEO+ARGUS(χ
d measurements)
0.498 ±0.032 ps-1
Average of 32 above 0.5055 ±0.0020 ps-1
LHCb D(*)
µ/OST(3 fb
-1, prel)
0.5036 ±0.0020 ±0.0013 ps-1
LHCb Dµ/OST,SST(1 fb
-1)
0.503 ±0.011 ±0.013 ps-1
LHCb B0d(full)/OST,SST
(1 fb-1
)0.516 ±0.005 ±0.003 ps
-1
LHCb B0d(full)/OST(0.036 fb
-1)
0.499 ±0.032 ±0.003 ps-1
BABAR D*lν/l,K,NN(23M BB
−)
0.492 ±0.018 ±0.013 ps-1
BABAR D*lν(part)/l
(88M BB−
)0.511 ±0.007 ±0.007 ps
-1
BELLE B0d(full)+D
*lν/comb
(152M BB−
)0.511 ±0.005 ±0.006 ps
-1
BELLE l/l(32M BB
−)
0.503 ±0.008 ±0.010 ps-1
BELLE D*π(part)/l
(31M BB−
)0.509 ±0.017 ±0.020 ps
-1
BABAR l/l(23M BB
−)
0.493 ±0.012 ±0.009 ps-1
BABAR B0d(full)/l,K,NN
(32M BB−
)0.516 ±0.016 ±0.010 ps
-1
D0 D(*)
µ/OST(02-05)
0.506 ±0.020 ±0.016 ps-1
CDF1 D*l/l
(92-95)0.516 ±0.099
+0.029 ps
-10.516 ±0.099
-0.035
CDF1 l/l,Qjet(94-95)
0.500 ±0.052 ±0.043 ps-1
CDF1 µ/µ(92-95)
0.503 ±0.064 ±0.071 ps-1
CDF1 Dl/SST(92-95)
0.471 +0.078
±0.034 ps-1
0.471 -0.068
OPAL π*l/Qjet
(91-00)0.497 ±0.024 ±0.025 ps
-1
OPAL D*/l
(90-94)0.567 ±0.089
+0.029 ps
-10.567 ±0.089
-0.023
OPAL D*l/Qjet
(90-94)0.539 ±0.060 ±0.024 ps
-1
OPAL l/Qjet(91-94)
0.444 ±0.029 +0.020
ps-1
0.444 ±0.029 -0.017
OPAL l/l(91-94)
0.430 ±0.043 +0.028
ps-1
0.430 ±0.043 -0.030
L3 l/l(IP)(94-95)
0.472 ±0.049 ±0.053 ps-1
L3 l/Qjet(94-95)
0.437 ±0.043 ±0.044 ps-1
L3 l/l(94-95)
0.458 ±0.046 ±0.032 ps-1
DELPHI vtx(94-00)
0.531 ±0.025 ±0.007 ps-1
DELPHI D*/Qjet
(91-94)0.523 ±0.072 ±0.043 ps
-1
DELPHI l/l(91-94)
0.480 ±0.040 ±0.051 ps-1
DELPHI π*l/Qjet
(91-94)0.499 ±0.053 ±0.015 ps
-1
DELPHI l/Qjet(91-94)
0.493 ±0.042 ±0.027 ps-1
ALEPH l/l(91-94)
0.452 ±0.039 ±0.044 ps-1
ALEPH l/Qjet(91-94)
0.404 ±0.045 ±0.027 ps-1
ALEPH D*/l,Qjet
(91-94)0.482 ±0.044 ±0.024 ps
-1
Heavy FlavourAveraging Group
∆md (world average 2015) = 505.5± 2.0 ns−1
B. Khanji, LHCb (Milano-Bicocca, INFN, CERN) ∆md at LHCb 22-March-2016 40 / 40