the road to the electroweak symmetry breaking 18 th january 2012 seminar at johns hopkins university...
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The road to the ElectroWeak Symmetry Breaking
18th January 2012Seminar at Johns Hopkins University
S.Bolognesi (Johns Hopkins University)
Outline
Status: CMS results in a nutshell, focusing on high mass H->VV
move to larger mass (>600 GeV beyond SM)
improve sensitivity to smaller xsec -> Vector Boson Fusion
The final arbiter: VV scattering
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)2
The Higgs boson and the ElectroWeak Symmetry Breaking (EWSB)
• control of V+jets background• jet merging• signal characterization (angular analysis)
What’s next ?
• control of VV background
Why we need the Higgs
The Higgs boson provides
1) an EXPLICATION of the W,Z mass (ie EWSB)
2) a DESCRIPTION of the fermions masses
1 is really fundamental to make the SM “working” (next slides) … even if not less arbitrary!
2 is just another way of formulating the same question:
why the fermions have those particular masses?
why the fermions have those particular Higgs couplings?
(SM works well without 2: just the fermio-phobic Higgs)
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)3
EWSB and the W, Z mass
BBmWWmBBWWL iiiigauge
22
2
1
2
1
4
1
4
1
kjijkiii WWgWWW
BBB Gauge invariance
SU(2)
U(1)EM
complex scalar doublet of SU(2)scalar potential (l>0, m<0) 22 V
0
v
0
2
1
02
1 vwith minimum (= empty state) atSU(2)
3 Goldstone bosons wi
hv
e vi
ii
0
2
1 2
1 physical scalar field 0h
(v = empty expectation value)
generic Gauge
Gauge unitario
4 Gauge fields combined into known vector bosons: W,Z with mass, photon massless
1 physical scalar field -> Higgs
hv
0
2
1
21
2
1 iWWW
22
3
gg
gWBgZ
4 Gauge fields Wim,Bm
22
3
gg
WggBA
222
4
1vgMW
2222
4
1vggM Z
02 AM
U(1)
or
×
01/18/2012 seminar 4
2
2
2
2
2
1
HH mt
t
ms
sts
vV V
Higgs and unitarity in VBF
VBF is the smoking gun of the EWSB !
Same behavior for all VV amplitudes
(s channel only)
(t channel only)
(t and u channels)
2
2
2
1
HLLLL ms
ss
vWWZZA
2
2
2
1
HLLLL mt
tt
vWZWZA
2
2
2
2
2
1
HHLLLL mt
t
mu
utu
vWWWWA
LLLL WWWWA
2
2
2
2
2
1
HHLLLL mt
t
ms
sts
vWWWWA
canale S canale T QGC
V V
V
VV -> VV
Vector Boson Fusion (VBF)
W,Z mass (-> longitudinal degrees of freedom) arise from the Higgs mechanism:without Higgs, W+
LW-L->W+
LW-L would
break unitarity
V
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)5
VBF and VV scattering VV scattering spectrum s(VV->VV) vs M(VV)
Whatever we will see or not see at low mass (<2×mW), the EWSB mechanism must be probed in the VV final state
search for possible resonances in VBF measurement of VV scattering spectrum
is the fundamental probe to test nature of Higgs boson or to find alternative EWSB mechanism
LSB<1TeVSB sector weakly coupled
SB sector strongly coupled
eg, strongly interacting light Higgs
SM No-HiggsLSB>1TeVUnitarity violation
other scenarios possible:
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)6
Higgs production and decay
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)7
CMS results
WW→lnqq, ZZ→llqq limited by huge V+jets background, taken from simu/data with large theoretical/statistical error
ZZ→llnn:
WW→lnln at high mass limited by signal << WW background (Df not effective)
• >400 GeV limited by Z+jets tail at high MET: not large but not well known (controlled with g+jets → statistical error+met uncertainty)
• 200-400 GeV limited by non-Z background (top, W+jets, WW)
ZZ→4l limited by statistics (only ZZ background: small and well known)
drives the UL for mH>300-400
drives the UL for mH 200-300
Future improvements ?
Combination of >5 different channels (ele, mu, btag, …) Robust!
Very optimized analyses, some space for further improvement. With higher lumi:• use shape analyses (where not yet done)
• extract background (norm and shape) from data with lower uncertainty
• extract signal with multidimensional fit (now only mZZ fit)
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)9
What’s next ?
higher mass
lower xsec
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)10
1 TeV masses: not anymore “the” Higgs→ General search for X→VV→4f:
→ importance of semileptonic final states
xsec larger than Higgs:
at high mass still very low number of events per fb-1
RS Graviton vs SM Higgs:
exotic models (eg, Technicolor, ExtraDimension, …)
first, repeat “Higgs” search for different spin, width resonance
CMS AN-2010-35: Angular Analysis of Resonances pp → X → ZZ
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)11
Available results: ZZ
low statistics
MET control V+jetsZZ→4l ZZ→llnn
CDF search for G→ZZ: same features discussed for high mass Higgs @ LHC
ZZ→lljj: large V+jets
arXiv:1111.3432v1
Available results: W+2jetsCDF “bump”
ATLAS & D0 xchecks
S.Bolognesi (Johns Hopkins University)13
Control of V+jets
Improving theoretical tools (Blackhat, Madgraph, …)
Control region (eg, Z→jj sidebands) has very low stat for M(lljj)~1 TeV
• rely on them to extrapolate at higher energy/multiplicity
• test them where we have statistics
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)14
QCD measurement (jet pT>20-30 GeV):
→ syst. dominated by jet scale, PileUp removal
V+jets Data unfolded for detector effects → compared to NLO (“hadron level”)
ATLAS:
01/18/2012 seminar 15
V+jets at Tevatron
At low pT, low multiplicity:
but results limited by systematics
interesting discrepancy data-NLO observed
→ new variables
D0 novel measurement: angular correlations have much lower systematics
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)16
High mass: what’s new ?
Can we simply keep the same Higgs analysis strategy? Not at very high masses!
New experimental issues at very high mass (1 TeV and above)
X → boosted VV → jet merging (and nearby leptons)
Unknown signal and very small background → no point in pushed optimization! Keep model independent approach as much as possible
How to disentangle the various models?
• peak → mass and width, xsec and BR
• spin! → angular analysis
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)17
>1 TeV M(ZZ)→4f : jet merging (1)
Jet merging: DR 0.8 (CA) → MX>600 GeV
DR 0.5 (Akt) → MX>900 GeV
approx
Handles to distinguish wrt to jets from QCD (eg, X→ZZ→2l2j VS Z+jets):
jet massttbar → WW→ln (jj) CMS EXO-11-006
1
(1 )Z
qq TZ
MR
pz z
( | | / | |)q Zz p p
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)18
jet radiation:
soft/collinear singularity in QCDno singularity, just decay!
Jet merging (2)
by David Krohn (Harvard)JHU seminar: Path-Integral Jetswww.pha.jhu.edu/groups/particle-theory/seminars/talks/F11/talk.khron.pdf
Handles to distinguish wrt to jets from QCD (eg, X→ZZ→2l2j VS Z+jets):
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)19
Jet pruning Remove all parts of the jet which are soft and wide angle
Boosted objects mass reconstruction improved
QCD jets mass substantially decreased -> lower backgrounds
Typically used for boosted top or boosted H→bb …
arXiv:0912.0033v1
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)20
Example in X→ZZ→2l2jFirst look at Z boosted (no numbers yet) … • MG 1500 GeV
• RS Graviton
• CA 0.8preliminary, A.Bonato, R.Covarelli
X->ZZ->2l2q signal Z+jets
before jet pruning
after jet pruning
before jet pruning
after jet pruning
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)21
Angular analysis (1) X→ZZ→4f decay kinematic fully defined by 5 angles
signal (MX 250):
MC from
Johns Hopkins
0+ , 0-
1+ , 1-
2+m , 2+L , 2-
X→ZZ Z decays
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)22
Can be clearly used to disentangle different signals… but what about background?
Already used in H→ZZ→2l2q: cut on likelihood
• Z+jets from MC: no correlations,
To optimize further (multidimensional fit), need full theoretical description of background:
qq → ZZ:
gg also available → can be used to disentangle qq-gg!!
• signal: ideal × uncorr. accept
(background from jj sidebands)
Angular analysis (2)CMS PAS -11- 017
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)23
What’s next ?
higher mass
lower xsec
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)24
Improve sensitivity
Improve theoretical control of • signal: → NNLO&NNLL effects, precise mass shape prediction, signal-background interference (back-up)
• background: → control of ZZ, WW ewk continuum
Factor 5 in luminosity wrt to present results
WHY? Models with lower xsec
HOW?
Ex of (light) composite higgs:
(studied in the Higgs Xsec WG and documented in 2 Yellow Report)
First LHC to Terascale Workshop (Sept 2011):LCH at LHC by J.R. Espinoza
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)25
Diboson production (WW,WZ,ZZ)
SM test: TGC fixed by ewk gauge structure
→ any deviation from SM in VV xsec is direct hint of NP in bosonic sector
Backgrounds for high mass Higgs→VV
gg→ VV
(LHC: few % of xsec with ~50% uncertainty)
qqbar → VV
WW,WZ,ZZ forbidden for ZZ
+ NLO qqbar +
forbidden for ZW
TGC
LHC focused on leptonic final state, Tevatron looked at semileptonic but limited by systematics (V+jets)
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)26
VV: theoretical prediction
qq→ZZ NLO + gg→ZZ
Uncertainty dominated by QCD part
01/18/2012 seminar 27
PDF+as
scale
WW in jet bins: uncertainty on (s >=N) + modeling: MC@NLO vs ALPGEN
ZZ→4l: measurement 4l is 0.5% of ZZ xsec but very clean
1.51.2( ) 3.8 ( ) 0.2( )ZZ stat syst
0.2( )lumi pb
observed events: 8expected events: 12.5±1.1
Dedicated EWK analysis with very low luminosity, Higgs results much beyond that
39%
16%
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)28
WW->lnln: measurement
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)29
Dedicated EWK results only with very low luminosity,
Higgs analysis much beyond that:
stat. and syst. errors included
37%
First search for a VBF resonance, feasible in 2012
Measurement of VV scattering spectrum with higher lumi (>50 fb-1)
From VBF to VV scattering
Tipical signature: forward-backward “spectator” jets with very high energy
JHEP 0704 (2007) 052
VBF ggH + 2jets
VBF ggH + 2jets
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)30
Higgs-like resonance in VBF
Today only WW→lnln. Expectations for next year:
• lumi > 10 fb-1• s(vbf) ~ 0.1×s(gg)• 0.5 effic. VBF cuts
VBF yields in 2012 ~ 0.5 gg yields of 2011 summer results,
ZZ→4l will be still limited by statistics
WW→lnln will improve S/B (signal/10, WW*as2)
semileptonic final states will have reasonable signal yields + much lower background than inclusive analysis
eg, ZZ→lljj : • signal yields for mH 300-500 ~ 15 – 5 events• V+(N+1)jets/V+N jets ~ 0.15 → asking 2 jets reduces background to 2%!• S/B may increase of a factor 2 (eff 0.5 × s 0.1 / 0.02)
RE-DO all the analyses in VBF mode (eg, fermiophobic)
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)31
with much less background:
summer2011
VV scattering spectrum In no Higgs case:
BUT increasing of xsec at high VV is suppressed by
→ small difference btw SM and violation of unitarity (no Higgs)
→ with proper cut (eg Dh jets) can be enhanced -> selection of the longitudinal W
SILH
W±W± scattering
• PDF• offshell bosons• unpolarized bosons
2
2
2
2
2
1
HH mt
t
ms
sts
v
LLLL WWWWA
reducible background
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)32
Longitudinal polarization
ud->udWW->udcs ud->udWW->udcs
mH 500 GeV noHiggs (unitarity violation)
WW tail (TT): neutrino
WW tail (TT): lepton
Higgs peak (LL): neutrino
Higgs peak (LL): lepton
Transverse distribution
Longitudinal distribution
Angular analysis can boost LL-TT separation (new!):
partonic study in the center of mass of W
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)33
VV scattering: interference effects
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)34
...
2signal
irreducible background (aEW6)qq->6f O(aEW
6)
WW approximated without interference
Big interference effects considered only in PhantomJHEP 0603 (2006) 093
Accomando, Ballestrero, Bolognesi, Maina, Mariotti
=
WW signal with “a posteriori” cuts
Summary
experimental issue: control of V+jets (jet pruning) several theoretical uncertainties on VV EWK continuum
angular analysis
Ingredients along the EWSB road:
search for VBF resonance and measuring of VV scattering spectrum
search for generic resonance X->ZZ->4f
Main steps:
The first aim of the Higgs search is the understanding of the EWSB-> focus on H->VV final state
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)35
BACK-UP
18th January 2012Seminar at Johns Hopkins University
S.Bolognesi (Johns Hopkins University)
The road to the ElectroWeak Symmetry Breaking
Sources
First LHC to Terascale Workshop (Sept 2011):
LCH at LHC by J.R. Espinoza
CMS AN-2010-35: Angular Analysis of Resonances pp → X → ZZ
by David Krohn (Harvard)JHU seminar: Path-Integral Jetswww.pha.jhu.edu/groups/particle-theory/seminars/talks/F11/talk.khron.pdf
Boson Boson scattering analysis by A.Ballestrero (INFN Torino)
LHC To Terascale Physics WS S.Bolognesi (Johns Hopkins University)37
Mass shape From Passarino talk at last LHC to Terascale WS
Present approx:• xsec for on-shell Higgs production and decay in zero width approx
• acceptance from MC with ad-hoc BW distribution
10-30% uncertainty on xsecfor mH 400–600 GeV
Study with QFT-consistent Higgs propagator in the YR2
Higgs qTqT > mH NNLO
qT << mH NNLL (resumming ln(mH2/qT
2))
HqT:
Uncertainties: • factor/renorm scale
• PDF • large mt approximation
• non perturb. effects(smearing with NP form factor)
LHC To Terascale Physics WS S.Bolognesi (Johns Hopkins University)39
Reweight to HqT
Very small effect on acceptance in 4l: 1-2%
HqT used to reweight full event generators (POWHEG at NLO)
mH 120 GeV mH 500 GeVH pT
H ymH 120 GeV mH 500 GeV
Powheg
Powheg re-weighted to Hqt
HNNLO
(larger if jet veto!)
LHC To Terascale Physics WS S.Bolognesi (Johns Hopkins University)40
(to be redone before PS)
Signal: jet counting Analysis in exclusive jet bins
(ex, WW+0,1,2 jets)
• if background depends on Njets• for VBF
→ theoretical uncert in jet bins to be combined with correlations
varying renormalization and factorization scales in the fixed-order predictions for each exclusive jet cross section σN
(results as 100% correlated)
different treatments of the uncontrolled higher-order O(α3s) terms
i.e., different NNLO expansions
inclusive xsec (σ≥Njets), as source of perturbative uncertainties
σN = σ≥N − σ≥N+1
with error propagation
LHC To Terascale Physics WS S.Bolognesi (Johns Hopkins University)41
Signal: jet veto Resummation of jet-veto logarithms ( ln(pcut/mH) ), induced by jet cut parameter pcut
direct exclusive prediction
from inclusive to exclusive prediction
LHC To Terascale Physics WS S.Bolognesi (Johns Hopkins University)42
Presently doable only on beam thrust variable (~raw approx of pcut)
and used to reweight MC@NLO
Signal-background interference Recent results for WW, but focused on low mass
Effect on gg→H→WW at LO
mT < mH
( arXiv:1107.5569v1 )
non-resonant diagrams can be large for mT > mH
Worth to investigate further at high mass?
also shape effects!
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)43
ZZ: theoretical prediction Single resonant contribution
qq→ZZ NLO + gg→ZZ
ZZ fully from MC, well under control
Interference in the final state with identical leptons
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)44
ZZ: t
heor
etica
l unc
erta
intie
s PDF+as
scale
qq gg
qq gg
01/1
8/20
12 s
emin
arS.
Bolo
gnes
i (Jo
hns
Hop
kins
Uni
vers
ity)
45
WW: theoretical uncertainties
WW taken from MC for large mH
→ gg+qq NLO available (MCFM)
WW from control region for mH<200 GeV (mll, Dfll)
in jet bins using uncert on (s >=N) + modeling: MC@NLO vs ALPGEN
PDF+as and scale uncertainty dominates
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)46
WW→lnln measurement
Background Cuts
Complex analysis (no mass peak→counting experiment, many backgrounds)
background estimate:
signal acceptance:
leptonic efficiency
jet-veto efficiency
missing ET uncertainty
theoretical (gg box, PDF)
W+jets tight lepton quality
top (b-)jet veto
Drell-Yan Z mass vetomissing ET
WZ, ZZ, Wg 2 leptonsestim
ated from
data→ estimated from MC
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)47
Main systematics:
50100150200
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eV/c
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)2 (GeV/cjjM50100150200
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WW/WZ→ln2j at CDF First observation: 5.4s (first evidence at D0 with 4.4s in 2008)
Much larger backgrounds, no resolution to distinguish W/Z→jj
fit to Mjj (3.9 fb-1) + matrix element method: (2.7 fb-1)
• discriminant exploiting full kinematic information, based on calculations of differential xsec of signal and background
QCD from data
• data-MC validation of input kinematic variables
• fit to shape of discriminant
(NLO expected )16.1 0.9pb( ) 16.0 3.3( )WW WZ stat syst pb
Sara Bolognesi (CERN) Physics in Collisions, August 201148
WZ/ZZ→l / +n nn 2b at Tevatron
• WZ → lnbb + ZZ → nnbb b-tag jets + missing ET (+ topological cuts)
Crucial for Higgs search (ZH→nnbb). Very complex analysis!
• No leptons! → huge background: multijets QCD, V+jets (from data)• very sophisticated techniques: b-tag probability with Boosted Decision Tree or Neural
Network which exploits much info and different variables
different channels combined (0,1,2 b-tag)CDF (2b-tags)
3.63.0( , ) 5.8WZ ZZ pb
( , ) 6.9 1.3( ) 1.8( )WZ ZZ stat syst pb D0:
CDF: (expected 4.6 pb)
(expected 5.1 pb)
Sara Bolognesi (CERN) Physics in Collisions, August 201149
ZZ→2l2n (5.9 fb-1)Shape analysis with fit to neural network
ZZ at CDF ZZ→4l (6 fb-1) excess of events at high MZZ (eg Randall Sundrum Graviton)
• But xsec still compatible with SM
• No excess in other final states
ZZ→2l2j
Control of Z+jets very challenging to measure ZZ xsec
control of Z+jets is crucial
Sara Bolognesi (CERN) 50
(NLO expected )
WZ→3l+n at LHC Very clean, low background
( ) 17.0 2.4( )WZ stat 1.1( ) 1.0( )syst lumi pb (NLO expected )
3.1 0.92.8 0.8( ) 21.1 ( ) 1.2( ) ( )WZ stat syst lumi pb
CMS:
ATLAS:
1.20.817.2 pb
Sara Bolognesi (CERN) Physics in Collisions, August 201151
1.10.818.75 pb
(NLO expected )
Recent WZ→3l+n at Tevatron
D0 with 4.1 fb-1
Possible only at hadron colliders (charged final state)
statistics 2 times smaller than LHC, while xsec is 6 times smaller
Shape analysis with fit to neural network
3.25 0.19pb
1.060.90( ) 3.90WZ pb
(NLO expected )
CDF with 7.1 fb-1
0.6 0.60.5 0.4( ) 3.9 ( ) ( )WZ stat syst pb 3.46 0.21pb
Sara Bolognesi (CERN) Physics in Collisions, August 201152
observed events: 34
expected signal: 23.3±1.5
expected background: 6.0±0.6
V+jets: ratios
Very well known theoretically → any deviation is hint of NP
Use high statistics W sample to predict Z+jets background for NP
CMS PAS EWK-10-011
Many systematics cancel out
01/18/2012 seminar S.Bolognesi (Johns Hopkins University)53
Z+b jets
• b-tagging with Secondary Vertex requirement or more sophisticated (eg Neural Network in D0)
• b-tag eff. measured separately from data• b-tag purity extracted from data (eg SV mass fit)
PDF of b quarks
fixed flavor scheme b only from gluon splitting
variable flavor schemegluon splitting integrated into the PDF
Benchmark for MSSM Higgs: fbbbar (large theoretical uncertainty on xsec)
Background to ZH(H→bbar), NP search with lept+b-jets
b-jets analysis:
(expected to coincide at NLO)
measurement of Z+b / Z+jets to cancel other (non-btag) systematics
Sara Bolognesi (CERN) 54)2Secondary vertex mass (GeV/c
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
)2Ev
ents
/ ( 0
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Datab-jetsc-jetsl-jets
-1 = 7 TeV, L = 36 pbs
CMS Preliminary
High efficiency b-tagging
)2Secondary vertex mass (GeV/c0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
)2Ev
ents
/ ( 0
.333
GeV
/c
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Datab-jetsc-jets
-1 = 7 TeV, L = 36 pbs
CMS Preliminary
High purity b-tagging
(GeV/c)b-leadT
p50 100 150 200 250
Even
ts/2
0GeV
/c
0
5
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Datatt
Z+bZ+cZ+l
-1 = 7 TeV, L = 36 pbsCMS Preliminary
High Purity b-tagging
(Z,b-lead)0 0.5 1 1.5 2 2.5 3
Even
ts/0
.2
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-1 = 7 TeV, L = 36 pbsCMS Preliminary
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(GeV/c)b-leadT
p50 100 150 200 250
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ts/2
0GeV
/c
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Z+jets
-1 = 7 TeV, L = 36 pbsCMS Preliminary
High Purity b-tagging
(Z,b-lead)0 0.5 1 1.5 2 2.5 3
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ts/0
.2
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Z+jets
-1 = 7 TeV, L = 36 pbsCMS Preliminary
High Purity b-tagging
Z+b results
(corrected for geometrical acceptance)
CDF (7.86 fb-1)
D0 (4.2 fb-1)NLO (mZ
2) 0.0192 +/- 0.0022
CMS
(fixed flavor)(variable flavor)
Similar results for muons
No statistical power yet to disentangle fixed VS variable flavor scheme
variable schemafixed
schema
0.9 data/MC b-tag eff.
b-tag eff. corrected results:
Sara Bolognesi (CERN) Physics in Collisions, August 201117
TO BE UPDATED soon with 1fb-1 → much better precision!
SSVHED-6 -4 -2 0 2 4 6
num
ber o
f eve
nts/
0.24
0
10
20
30
40
50
60
70
80
90
Data
+charm+W
+light+W
top
Other bckg.
CMS preliminary
= 7 TeVs at-136 pb
SSVHED-6 -4 -2 0 2 4 6
num
ber o
f eve
nts/
0.24
0
10
20
30
40
50
60
70
80
90
Data
+charm-W
+light-W
top
Other bckg.
CMS preliminary
= 7 TeVs at-136 pb
[GeV]TM60 80 100 120 140 160
num
ber o
f eve
nts/
2 Ge
V
0
200
400
600
800
1000
1200
Data
+charm+W
+light+W
top
Other bckg.
CMS preliminary
= 7 TeVs at-136 pb
[GeV]TM60 80 100 120 140 160
num
ber o
f eve
nts/
2 Ge
V
0
100
200
300
400
500
600
700
800
900
1000
Data
+charm-W
+light-W
top
Other bckg.
CMS preliminary
= 7 TeVs at-136 pbW+c Dominated by sg→Wc• dg→Wc Cabibbo suppressed• W+b even more suppressed
LHC: W+c ~ 10% W+jets (W+b negligible)
→ Wcbar (Wc) measures the sbar (s) PDF
MC predictions fit
lifetime-tagging
CMS (unexpected! just a first go):
Tevatron: W+c ~ 5% W+jets
semileptonic charm decay + opposite charge W and c
CDF (4.3 fb-1):
(NLO calculation )
( ) ( ) 33.7 11.4( ) 4.7( )Wc BR W l stat syst pb
16.5 4.7 pb
Sara Bolognesi (CERN) Physics in Collisions, August 201120