lhcb physics reach
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Marco Musy Fermilab 3th May 2003 (1)
LHCb Physics LHCb Physics reachreach
Marco MusyMarco MusyUniversità di Milano Bicocca
and INFN Milano
LHC2003 International Symposium
Fermilab, 3th May 2003
Marco Musy Fermilab 3th May 2003 (2)
Ambitious physics goals of LHCbAmbitious physics goals of LHCb
Precision CPV measurements, using also pure hadronic and multi-body final states(Bd , Bd D
Exploit CPV in new decay channels as in Bs
(BsKK, BsDsK, BsJ/ Rare b-decays
(BdKBdKBsNew particles may show up in loop diagrams,
overconstrain will allow to disentangle SMcomponents from the new-physics ones
Overconstrain the unitarity triangles Search for New Physics beyond SM
NP?NP?b
d d
b
t
t
High statistics is a requirement
Marco Musy Fermilab 3th May 2003 (3)
CPV from CPV from LHCb in one LHCb in one
yearyear
sin
|Vtd/Vts|
|Vub/Vcs|
now
2007
2008
LHCb
and not well known
Bs mixing
BdJ/KS Bd D*
|Vub/Vcs|
• If New Physics is there
LHCb experiment can spot it in 2008 !LHCb experiment can spot it in 2008 !
BdJ/KS Bd
BsJ/ Bs DsK
Marco Musy Fermilab 3th May 2003 (4)
Experimental Experimental challengechallenge
• LHCb has to deal with a large variety of final states with different LHCb has to deal with a large variety of final states with different topologiestopologies• Hot pp environment needs a robust trigger Hot pp environment needs a robust trigger bb inel.~ 0.01 (bb~ 500 b),
many particles are not associated to b-hadronsmany particles are not associated to b-hadrons• b-hadrons do not evolve coherentlyb-hadrons do not evolve coherently
• High bb yield, High bb yield, 1012/year of Bd, Bs , baryons, Bc with c7mm
HIGH STATISTICSBd K*
BdJ/
Marco Musy Fermilab 3th May 2003 (5)
Detector has undergone a reduction of material in front of RICH2
(60% 40% for X0, 20% 12% for I) Less interactions in detector, Level-1 Trigger includes momentum measurement Technologies have not changed September 2003: “Detector Reoptimization TDR” and “Trigger TDR” Construction phase is in good shape ( T. Nakada talk)
LHCb LHCb detectordetector
Marco Musy Fermilab 3th May 2003 (6)
• MC Pythia 6.2 tuned on CDF and UA5 data• Multiple pp interactions and spill-over effects included
• Complete description of material from TDRs• Individual detector responses tuned on test beam results
• Complete pattern recognition in reconstruction: MC true information is never used
• 1M inclusive bb events produced in Summer 2002• New “Spring” production ready: 10M events for September
TDRs• Sensitivities quoted here are obtained by rescaling earlier
studies to the new yields
Fully simulated bb event in Fully simulated bb event in Geant3Geant3
Marco Musy Fermilab 3th May 2003 (7)
VELO
Bs mixing
Measure ms
at 5
up to 48 ps-1
VELO
PV ~
47m SV
~170m
Main Main performancesperformances
see dedicated talks!see dedicated talks!
Tracking
• <Ntracks>= 27 “physics” tracks
track ~ 95% p>5 GeV/c
“ghost” rate ~ 8% @pT>0.5GeV
2<p<100 GeV/c
<(KK)>= 88%
<(K )>=2.7%
RICH
e PID
<()>= 86%
<(ee )>= 78%
<( e,)>=1%
RICH-1
Marco Musy Fermilab 3th May 2003 (8)
Efficiency includes:
Geometrical acceptance, acc
including detection efficiency, material
Trigger efficiency: Level-0 && Level-1, L0,1
including expected Pile-up rate veto
Reconstruction efficiency (tracking, calorimeters, PID), track
Selection cuts efficiency to reconstruct the final state and reject background, cut
Event Event yieldyield
untaggedChannel tot Yield
B0 0.78 % 27 k
B0 K 0.85 % 115 k
Bs KK 0.94 % 35 k
Bs Ds 0.26 % 72 k
Bs Ds-K+ 0.34 % 8 k
Bs J/ 1.66 % 109 k
Bs J/e-e 0.29 % 19 k
B0 J/KS 0.76 % 119 k
B0K0 0.09 % 20 k
1 year = 2 fb 1 year = 2 fb -1-1
LL = 2x10= 2x103232 cm cm–2–2ss--
11
yield L(t)dtyear bb 2 Prob(b bhadron) BRi
i tot
norm. to 4
acc* track* cut* L0* L1= 13% * (96%)2 * 22% * 61% *
51%
Marco Musy Fermilab 3th May 2003 (9)
Flavour Flavour taggingtagging Knowledge of flavour at birth is
essential for the majority of CPV measurements
Opposite side lepton tag ( b l ) Opposite side kaon tag ( b c s ) - unique to LHCb, BTeV - correlated to hadron trigger
Same side pion and kaon tag (with coming either from B** or
fragm. successfully used by CDF already)
Vertex charge tagging
l
B0
B0
D
K-
•Only single particle tagging (e, , K) from opposite side B decay used
in this presentation = 0.40,D = 0.40 DD22 = 6.4% = 6.4%
•The new MC data give similar results
b
b
d
u
d
u
B0
+
Marco Musy Fermilab 3th May 2003 (10)
Flavour taggingFlavour tagging
Work is in progress to update and improve the efficiencies
Method tag ωtag eff
12.4 35.5 1.0 ±0.1
e 7.7 43.3 0.14 ±0.07
K (OS) 26.3 36.2 2.1 ±0.3
K (SS) 17.3 29.7 2.9 ±0.3
Vtx Charge 23.9 40.0 0.9 ±0.2
TOTAL 65.8 34.8 6.1 ±0.4
Typical tagging efficiencies:
in Bs K, KK, Ds channels (after L0*L1 trigger, any nr of collisions)
Bs Same Side
IP/
Bs Opposite Sideeff
K-tag
K-tag
Marco Musy Fermilab 3th May 2003 (11)
BB(s)(s) KKK K KK
Selection cuts on Signal charged tracks, PID
Reconstructed B
max pT min IP/
pT(B) L/L
incl. bb
signal
Proper time = 41 fs
=18 MeV/c2
92% purity
Combinatorial bb bckgr, can be fully rejected even relaxing mass cut S/B S/B ~~ 1 1
Marco Musy Fermilab 3th May 2003 (12)
from Bfrom B(s)(s) K KK K
(proposed by R. Fleischer )
• Relies on “U-spin” symmetry assumption (ds) which is the
only source of theoretical uncertainty
• Clean measurement of
assuming from Bs J/ and from B J/Ks
• Sensitive to New Physics contribution which can be
pointed out
by comparing with obtained from DsK
Marco Musy Fermilab 3th May 2003 (13)
from Bfrom B(s)(s) K KK K
dirCPA mix
CPA Evaluation of and sensitivity
from time-dependent measured asymmetry
B0 + - BS K+ K-
yield 27k 35k
B/S 0.8 0.55
xq 0.755 20
D2 0.064 0.064
-0.30 0.16
0.58 -0.17
0.0 0.0
dirCPAmixCPA
input values
BB0 0 ++ -- BBSS K K++ K K--
02
sinh2
cosh
)sin()cos()(
A
xAxAA
mixCP
dirCPth
CP
Marco Musy Fermilab 3th May 2003 (14)
tagging efficiency
BBSS K K++ K K--
BB0 0 ++ --
BBSS K K++ K K--
53.0),(
054.0)()(
mixCP
dirCP
mixCP
dirCP
AACorr
AA
200@
0),(
043.0)()(
ss
mixCP
dirCP
mixCP
dirCP
x
AACorr
AA BBSS K K++ K K--
increasing xs
from Bfrom B(s)(s) K KK K
In one year:
CP asymmetry can be measured in Bs KK up to xs=40 with an error increase of a factor 1.6
For xs=20 ~ 3o New
!
Marco Musy Fermilab 3th May 2003 (15)
Decay is polluted by penguin diagrams
Penguin/Tree might be as high as 0.2
RICH PID and hadron trigger are fundamental
If |P/T| will be known to ±0.1 then
55°< °< 1010°° (depending on parameter value)
from Bfrom B00
Marco Musy Fermilab 3th May 2003 (16)
BBss DDssDDssKK Bs K
K
, K
Ds
When selecting Bs Ds K
BR(Ds K)/BR(Ds
) = 1/15 while
(Ds K)/ (Ds
) = 70 thanks to the RICH PID
Dsmass (GeV)
~ 6.5 MeV/c2= 168 m
= 418 m
72k Ds
8k Ds K
Bs vtx resolution (mm)
Ds vtx resolution (mm)
Marco Musy Fermilab 3th May 2003 (17)
Needed:
Hadronic trigger
K/separation
Good proper time resolution
Sensitivity depends upon
• relative amplitudes
• strong phase difference• values of , ms s s
For ms=20 ps–1:
1010oo
For ms=30 ps–1:
1212ooIn one year: 8k BsDsK reconstructed
events
fromfrom BBss D D--s s KK+ + , D, D++
s s
KK--
From the measurement of 4 time-dependent asymmetries one gets (with from BsJ/
same order tree level amplitudes (3) : large asymmetries, NP contributes unlikely
Same principle holds for B0 D*, (study at the time of TP gives similar precision on , a new evaluation is under way)
Marco Musy Fermilab 3th May 2003 (18)
fromfrom BBss J/J/
In SM S 10-
2 Sensitive to New Physics effects
in the Bs-Bs system In one year:
109 k events Bs J/
19 k events Bs J/e+e
Determination of s
ssss 0.03 0.03
for ss = 0.15
J/is not CP eigenstate:
needs fit to angular distributions of decay final states as a function of
proper time
Assuming ms=20 ps–1:
22oo 36±1 fs
will be
updated
for TDR
Marco Musy Fermilab 3th May 2003 (19)
fromfrom BB00 J/J/KKss
The ‘gold plated’ channel at B-factories
Precision measurement of this parameter is very important:
=0 in SM =sin 2
LHCb will bring a lot of statistics to this channel, which can be used to look into higher order effects, and fit Adir
In one year with 119k events: sin sin 0.02 0.02
Comparing with other channels may indicate NP in penguin diagrams
will be
updated
for TDR
Marco Musy Fermilab 3th May 2003 (20)
BR( B K ) = (4.30.4) 105
Direct CP violation in SM <2%
Sensitive to New Physics effects
Rare decays:Rare decays:BB K K
In one year:
20k events B K(K)
triggered and reconstructed
Mass resolution ~72 MeV
Background from BKcan be rejected using K helicity
W
b u,c,t s
Marco Musy Fermilab 3th May 2003 (21)
LHCb preliminary study
(ppBc) ~300 nb 109 Bc/ year
Bc J/BR ~10-2)
~ 2% 12k events/year
Background from B J/X and prompt
J/reduced cutting on the distance between primary vertex and Bc vertex
BBc c mesons mesons
CDF: mBc= 6.4 0.4 GeV, Bc ~ 0.5 ps
LHCb acceptance ~30%
M( J/GeV/c2
Possible CPV with Bc J/D, Bc DsD, DD, ...
Precision measurement of mass, life-time
p (GeV)
Marco Musy Fermilab 3th May 2003 (22)
Current status of LHCbCurrent status of LHCb Physics Reach in 1 year Physics Reach in 1 year (2fb(2fb–1–1))
ChannelChannel Yield Yield PrecisionPrecision**
Bd J/Ks 119 k 0.6o
Bs DsK
Bd , Bs KK
8 k 27 k, 35 k
10o
3o
Bd 27 k 5o- 10o
Bs J/ 128 k 2o
|V|Vtdtd/V/Vtsts Bs Ds 72 k ms up to 58 ps
rare rare decaysdecays
Bd K 20 k
*Precisions obtained by scaling old results with the new yields All numbers will be updated together with more channels in the re-optimization TDR (September 2003)
Marco Musy Fermilab 3th May 2003 (23)
Possible sources of systematic uncertainty:• Asymmetry of b vs b production• Detector efficiencies which depend on charge can bias tagging efficiencies
can fake CP asymmetries• CP asymmetry also in background processes
Systematics in CPV measurements
Alternate runs, swapping the orientation of magnetic field
Use control samples available with high statistics: Bs Ds72k events/year
B0 J/ K* 600k events/year B J/ K600k events/year
Study CP asymmetries in the B mass side bands
(from Technical Proposal)
Marco Musy Fermilab 3th May 2003 (24)
ConclusionConclusion
LHCb is a dedicated detector for B physics measurements in many channels from the beginning
of LHC
A very precise determination of CKM unitarity triangle will be possible
Detector performances are being evaluated with a realistic and complete Monte Carlo simulation
LHCb offers an excellent opportunity to spot New Physics signals beyond Standard Model very soon at
LHC
Marco Musy Fermilab 3th May 2003 (25)
back-up slides
Marco Musy Fermilab 3th May 2003 (26)
00 reconstruction reconstruction•PreShower (scintillator+Pb+scintillator) 2X0
•ECAL (Pb+ “shashlik” scintillator) 25X0 (E)/E=10% /E 1.5%
•HCAL (Fe+scintillator) 5.6 I (E)/E=80% /E 10%
Purity ~20% in range 0.1<m <0.17 GeV/c2
pT>200 MeV
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