precision measurement of b0 meson oscillation frequencyprecision measurement of b0 meson oscillation...
TRANSCRIPT
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
-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
(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
Even
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
Even
ts /
0.0
5
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 /
0.0
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