1. Status of the LHCb Experiment
Presented in LHCC Closed Session
9 July 1998
T. Nakada
And
H.J. Hilke
On behalf of the LHCb collaboration

2. Outline of the presentation
1) CP physics programme of LHCb (TN,35’)
2) Recent development on the detector R&D
3) Installation Plan and Milestones
4) Cost
(HJH,10’)

3. CP Physics Programme of LHCb
If there is nothing else but the standard model,
|Vcb|, |Vub| B-meson decays
Dmd Bd-Bd oscillations
will fix all the Wolfenstein’s parameters,
A, r and h (l is well known). _ _ _ b c t b d A2 W W W t b u d b
A2 (r2 + h2 ) W
A2 [(1 - r)2 + h2]

4. CKM matrix relevant for B Physics at LHCb
(CP violation is all due to ≠ )
  
i  
i i 
  i
  
i   
VCKM =

5. Vtd  e-ib Vub  e-ig Dmd Unitarity triangle Gbu b and g are
From the neutral kaon system h > 0
Dmd
Unitarity triangle h
Gbu g b 1 r
b and g are
defined by the
sides
Vtd  e-ib
Vub  e-ig

6. Penguin effect is negligible CP violation in
Bd  J/y KS v.s. Bd  J/y KS
measures the phase of Vtd, i.e. b
compare two b measurements = consistency test _
HB-B  (Vtb* Vtd )2  e2ib _ _ _ t b c
J/y b d _ W c Bd
Bd- Bd W W s KS t d b d d c c
Penguin effect
is negligible
t,c,u g b s Bd W KS d d

7. a) There will be already a sign of new physics:
By 2005, CLEO, BaBar, BELLE, CDF, D0
and HERA-B will have
-accurate |Vub|, |Vcb| and
-b from CP violation in Bd  J/y KS with s ~ 0.025
Possibilities are
a) There will be already a sign of new physics:
-precision measurements in different decay modes
in order to pin down the details of new physics.
b) Measurements look “consistent” with the Standard
model.
-what could happen?
Let’s make the following “interesting” scenario.

8. HB-B  [{(1 - r)2 + h2}+ r2db] e2i(b + fdb)
A model for new physics _
HB-B  [{(1 - r)2 + h2}+ r2db] e2i(b + fdb) _ _ _ _ _ t b d b d
new
FCNC _
Bd- Bd
Bd- Bd W W t d b d b _
HB-B  [ l-2 + r2sb ] e-2i(dg + fsb) _ _ _ _ _ t b s b s
new
FCNC _
Bs- Bs W W t s b s b

9. Vtd  e-ib Measured Gbu hD the CKM triangle h b defined by the
Measured Dm(Bd)  (1 - r)2 + h2 + rdb h
(1 - r)2 + h2 from SM box
Measured Gbu
b defined by
the CKM triangle
Vtd  e-ib hD h g r 1 gD
b defined by the
measured triangle.
dgD = l2hD dg = l2h

10. CP measurement and triangle measurements agree each other.
CP violation in
Bd  J/y KS v.s. Bd  J/y KS
measures bJ/yK = b + fdb
If the model is such that numerically fdb ≈ bD - b
“bJ/yK = bD ”
CP measurement and triangle measurements agree each other.
 Look consistent with the Standard Model!

11. BABAR and BELLE may have difficulty to access g+b
CP violation in Bd  p+ p-
-experimental problem
small branching fraction ≈ 710-6 (CLEO)
-theoretical problem
large penguin contribution u W p-
t,c,u p- b d W d Bd u g b u u Bd p+ p+ d d d d
CLEO: Br(p+p-)<Br(K+p-)  penguin is large s b u d Bd p+ W g
t,c,u K-

12. Bd  p+ p- can be used only if we know penguin/tree.
CP violation in Bd  p+ p- is not really possible for
CDF and D0: no particle ID, HERA-B: not enough statistics
Bd  p+ p- can be used only if we know penguin/tree.
A way out:
measure Br(p+ p0) and Br(p0 p0)  not enough statistics
CP violation in Bd  r+p-, r-p+, r0p0
-experimental problem
decay time dependent Dalitz plot analysis
 not enough statistics
-theoretical problem
assume p+p-p0 to be always rp

13. CDF, D0 and HERA-B may be able to measure Dm(Bs)
If Dm(Bs)/Gb <20. Does this help? Not really.
-It helps to reduce hadronic uncertainties (fB2B)
-It is interesting if it is really large; new physics.
But it is out of their sensitivities.

14. How can LHC attack the problem?
1) Improve bJ/yK measurement.
ATLAS, CMS: s ~ 0.02/year
LHCb: s ~ 0.01/year
2) Measure other angles using Bs
CP violation in BsJ/yf measures dgJ/yf = dg + fsb
If the model is such that numerically fsb ≈ dgD - dg
“dgJ/yf = dgD ”
Still looks consistent.
ATLAS, CMS: s ~ 0.03/year

15. LHCb can do much more! CP violation in
Bs  Ds+K-, Ds-K+ Bs  Ds+K-, Ds-K+
measures gDsK = g - 2dg - 2fsb  g - 2dgD
There is no more freedom left to make
gDsK = gD - 2dgD
Measured gDsK disagrees with what one expects from the triangle relation  New Physics
Only LHCb can measure this: K/p separation
s ~ /year (radian)
no hadronic uncertainty

16. 3) Further CP violation studies with Bd requiring
3) Further CP violation studies with Bd requiring very high statistics (difficult for BaBar and Belle).
Bd  D0K*0, D0K*0,D1,2K*0
measure g.
Bd  D*+p-, D*-p+ Bd  D*+p-, D*-p+
measure 2b + fdb + g; 2bD + gD i.e. inconsistent
Only LHCb can do these: K/p separation
hadron trigger
No hadronic uncertainties.

17. An example of shopping list: LHCb ATLAS/CMS
Bd  J/yKS  
Bs  J/yf  
Bs  DSK   (PID)
Bd  DK*   (PID,Trigger)
Bd  D*p   (PID)
Bd  pp   (PID)
Bd  Kp (CP in gluonic penguin)   (PID)
Bd  rp  ?
( BaBar 160 events, LHCb 670 events)
Bs  K*g (CP in radiative penguin)  ?
Bs  K*l+l- (CP in radiative penguin)  
Bs oscillations, xs up to
Bs  m+m-  

19. Physics capability of the LHCb detector is due to:
-Trigger efficient for both lepton and hadron high pT hadron trigger 2 to 3 times increase in pp,Kp,D*p,DK*,Dsp,DsK … Dsp: ATLAS=3k, CMS=4.2k, LHCb=34k
-Particle identification e/m/p/K/p pp,Kp,D*p,DK*,Dsp,DsK
-Good decay time resolution e.g. 43 fs for Bs  Dsp, 32 fs for Bs  J/yf ATLAS(Dsp )=73 fs, CMS(J/yf)=68 fs
-Good mass resolution e.g. 11 MeV for Bs  Dsp, 17 MeV for Bd  p+p ATLAS(Dsp)=40 MeV, CMS(p+p- )=31 MeV
particle ID + mass resolution  redundant background rejection

20. Importance of particle identification
Br: Bd = , Km = 
BsKK = , Km = 
eff. = 85%
m =
17 MeV/c2

21. Major background: Bs  Ds(No CP violation)
Bs  DsK
Major background: Bs  Ds(No CP violation)
Importance of particle identification and mass resolution

22. Performance figures are supported in particular by:
- GEANT detector simulation
- Low luminosity (21032 cm2s-1) needed
- Flexible and robust early level trigger
Level-0: High pt e, m, h, Level-1: Vertex
- Conservative approach to the detector

23. Trigger -Not relying on a particular single component.
-Trigger operating point can be adjusted to the running condition without loss in physics.
Example:
Thresholds for three different L0 trigger components can be adjusted depending on the running condition.

24. Examples for the technology choice are
Micro-strip Si vertex detector with short r-f strips.
occupancy, thickness, resolution, no. of channels
 optimal solution (c.f. pixel)
established technology.
placed at 1cm from the beam,  safe from radiation damage.
RICH,
HPD with back up photon detector:
88 multi anode PMT.
RICH-1 performance proven by the prototype

25. LHCb Organisation: System Coordinators Working group coordinators
Vertex: T. Ruf Inner Tracker: U. Straumann Outer Tracker: B. Koene RICH: D. Websdale Calorimeter: J. Lefrancois Muon: B. Schmidt Trigger: H. Dijkstra Data Handling: J. Harvey Magnet: W. Flegel Electronics: J. Christiansen
Experimental Area: D. Lacarrere
Working group coordinators
Tracking: W.Ruckstuhl Particle ID: R. Forty
Physics: T.Nakada

26. Detector System System Participating Institutes
Vertex CERN, Free Univ. Amsterdam, Glasgow, Kiev, Lausanne, Liverpool, MPI Heidelberg, NIKHEF
Inner Tracker Univ. Heidelberg, PNPI, Santiago
Outer Tracker Beijing, Dresden, Free Univ. Amsterdam, Freiburg, Humboldt, NIKHEF, Univ. Amsterdam, Utrecht
RICH Cambridge, CERN, Genoa, Glasgow, ICL, Milan, Oxford
Calorimeter Bologna, Bucharest, Clermont-Ferrand, IHEP, INR, ITEP, Kharkov, Lebedev, Orsay
Muon CERN, Hefei, Nanjing, PNPI, Rio de Janeiro, Rome I, Rome II, Shangdong, Virginia
Trigger Bologna, CERN, Espoo-Vantaa, Univ. Heidelberg, Lausanne, Marseille, NIKHEF, Rice, Virginia
Data Handling Cambridge, CERN, Espoo-Vantaa, Lebedev, Marseille, Oxford, Orsay, Rio de Janeiro
Magnet CERN

27. Conclusions:
The LHCb experiment is essential for studying CP violation in the B meson system in order to discover new physics.
The LHCb detector described in the Technical Proposal fulfils the necessary requirements; i.e. particle identification, efficient trigger and good decay time and mass resolution.
We believe that the LHCb collaboration is capable of doing this experiment.