1. The Physics of SuperB - Experimental
Detector requirements and physics performance required to achieve the physics goals
David Hitlin
INFN SuperB Review
November 12, 2007

2. This talk will primarily address two topics:
Design considerations for an appropriate detector for a collider like SuperB
Note that detector technology issues for SuperB, a low-emittance, low current collider, are quite different from those for a high current machine such as SuperKEKB
The physics goals are also different from those of BABAR/Belle
How can we upgrade an existing detector (using BABAR as an example) to better match the new physics goals ?
With such an upgraded detector, can we reach adequate levels of sensitivity to be relevant to the elucidation of the details the flavour sector of any new physics found at the LHC ?
David Hitlin INFN SuperB Review Nov. 12, 2007

3. Primary physics objectives of a Super Flavour Factory
Are there new CP-violating phases ?
Are there new right-handed currents ?
Are there new loop contributions to flavour-changing neutral currents
Are there new Higgs fields ?
Is there lepton flavour violation ?
Is there new flavour symmetry that elucidates the CKM hierarchy ?
What are the requirements for a detector that can address these questions in a asymmetric e+e- environment ?
David Hitlin INFN SuperB Review Nov. 12, 2007

4. Doing the physics: environment and event characteristics
The primary physics goals of SuperB differ from those of BABAR and Belle, which showed that the CKM phase is consistent with all known CP-violating phenomena and that the Unitarity Triangle could withstand a detailed series of over-constrained tests
The SuperB physics goals are the next logical step, using rare heavy flavour decay phenomena as a sensitive probe of physics beyond the Standard Model
The basic physics environment (e+e- annihilation from GeV) is familiar, but the physics objectives differ, and the luminosity of SuperB is increased by nearly two orders of magnitude over the current machines
Thus the background environment is different and the trigger requirements differ from those of PEP-II/KEKB
In what way do these differences reflect into the design of the SuperB detector?
This talk will review the machine-produced environment and event characteristics and use several specific physics examples to arrive at a set of design criteria for the SuperB detector
Specific design details will be presented in the following talks
David Hitlin INFN SuperB Review Nov. 12, 2007

5. David Hitlin INFN SuperB Review Nov. 12, 2007
Trigger rates and DAQ
Physics rate at 1036 are substantial
Due to the low emittance design, machine backgrounds appear to be tolerable and a small radius beam pipe is feasible, allowing use of a reduced energy asymmetry
Physics demands an open trigger as is traditional in e+e-
Demands on the trigger and DAQ are thus substantial, but LHC-derived technologies are sufficient
Further details in later presentations
David Hitlin INFN SuperB Review Nov. 12, 2007

6. Choice of energy asymmetry
Smaller SuperB beam sizes at the IP allow the use of a smaller beam pipe (radius 1 cm)
This permits a thinner beam pipe in radiation lengths
First track measurement at 1.2 cm
Smaller asymmetry improves solid angle coverage
7x 4 GeV
Boost bg=.28
PEP-II: bg =0.56
David Hitlin INFN SuperB Review Nov. 12, 2007

7. David Hitlin INFN SuperB Review Nov. 12, 2007

8. Solid angle coverage 7x4 GeV
Solid angle (% of 4p)
200
300
600
400
500 D
(%)
700
800
Forward coverage (mrad)
Rear coverage (mrad)
7x4 vs 8x3.5 GeV
Coverage of BABAR: 300 mrad forward
mrad backward
David Hitlin INFN SuperB Review Nov. 12, 2007

9. Final state reconstruction efficiency
In B meson decay <nch>=5, <ng>=5
t decay is dominated by 1 and 3 prong topologies
We expect recoil physics to be an important part of the program
Both B mesons must, perforce, be reconstructed
In most, but not all cases, the object of photon detection is p0 reconstruction. Thus ~ eg2
The effective solid angle for complete final state reconstruction is determined by the system which has the minimum solid angle coverage
evertex  etracking  ePID  eg 
David Hitlin INFN SuperB Review Nov. 12, 2007

10. David Hitlin INFN SuperB Review Nov. 12, 2007
B0fKs reco efficiency vs solid angle coverage
J. Back
David Hitlin INFN SuperB Review Nov. 12, 2007

11. David Hitlin INFN SuperB Review Nov. 12, 2007
Track momenta and polar angle distribution
David Hitlin INFN SuperB Review Nov. 12, 2007

12. David Hitlin INFN SuperB Review Nov. 12, 2007
Track momenta at lower Ecm are substantially softer
SuperB can run at lower Ecm for specific D and t studies, as well as at the other U resonances (particularly U (5S) ) (with bg =0.28)
1 month of SuperB running at
y(3770) or for below charm charm threshold yields 10X final BES-II data
David Hitlin INFN SuperB Review Nov. 12, 2007

13. Center-of-mass energy spread
Many analyses use cuts on m ES and DE to extract a signal
Center-of-mass energy spread determines m ES and thus the signal-to-noise ratio in rare B decays
Center-of -mass energy spread also determines the effective cross section on the U (4S) , U (5S) or y (3770) resonances
This was a concern in earlier incarnations of SuperB which had highly disruptive collisions but is no longer an issue
PEP-II, SuperB
(4S)
David Hitlin INFN SuperB Review Nov. 12, 2007

14. DE resolution
p+p-
D*p
David Hitlin INFN SuperB Review Nov. 12, 2007

15. Recoil physics at the ¡ (4S)D* p e+
Breco
Brecoil Xu n
“The Recoil Method “ will be of increasing importance at SuperB
Fully reconstruct one of the two B’s in hadronic modes and/or semileptonic modes as well and do it with high efficiency
The rest of the event is the other B, whose four-momentum is known
You then have a single B beam:
reduced backgrounds for rare decay studies, especially those with neutrinos, and
reduced systematics for precision Vcb, Vub studies
Semileptonic decays
B D(*)n, B (p,r)n, BXc,un
B D(*)tn (sensitive to New Physics)
Purely leptonic decays Btn, ….
B Knn
B invisible
B Xsg
David Hitlin INFN SuperB Review Nov. 12, 2007

16. The recoil method
Subtract combinatorial background
Breco (recoil) kinematics known with small uncertainties
Breco (recoil) flavor determined
Breco (recoil) charge (B0- B+ separation)
Direct mX reconstruction
Lepton charge – Breco (recoil) flavor correlation
Kinematic constraints on recoil B
Low efficiency - can be tuned for purity
purity
yield
Xcn
Xun sg
Dtn
p+n
p0n tn
p+tn
Knn
Luminosity (ab-1)
Number of recoil events
Reconstructed B mesons
Luminosity (ab-1)
David Hitlin INFN SuperB Review Nov. 12, 2007

17. Acceptance studies
BKGD/Signal
with smearing
Many of the main physics objectives of SuperB involve missing energy signatures
Detector requirements
Use of the recoil technique
Excellent reconstruction efficiency for hadronic B decays, especially those involving D*s
Excellent particle ID
Hermeticity
Improving backward calorimeter coverage can pay large dividends in signal/background
Study using Btn benchmark
Forward polar angle coverage (radians)
BKGD/Signal
with smearing
Backward polar angle coverage (radians)
M. Mazur
David Hitlin INFN SuperB Review Nov. 12, 2007

18. David Hitlin INFN SuperB Review Nov. 12, 2007
LFV in t decays: SuperB capability
tg : the ultimate sensitivity will be affected by e+e-t+t-g t+tag t-  m-nng irreducible background. When that limit is reached, the sensitivity scales as 1/sqrt(L). For ~75/ab 5 yrs) expect ~2x10-9
SM t decay
(1- or 3- prong)
(1 or 2 )
CM frame
Signal decay
LFV: no pmiss
(MEC) ~9MeV
 (E) ~50MeV
David Hitlin INFN SuperB Review Nov. 12, 2007

19. LFV in t decays: SuperB capability
t , hh’ : the sensitivity is not likely to be limited by irreducible backgrounds: the sensitivity scales as 1/L. For 5 yrs expect ~2x10-10
Principal backgrounds
David Hitlin INFN SuperB Review Nov. 12, 2007

20. LFV in t decays: SuperB capability
SuperB sensitivity directly confronts many New Physics models
BABAR
SuperB sensitivity
For 75 ab-1
David Hitlin INFN SuperB Review Nov. 12, 2007

21. Limits are highly constraining (example tmg)
David Hitlin INFN SuperB Review Nov. 12, 2007

22. Comparison to Snowmass Points and Slopes
Argand and Herrero arXiv: v1 [hep-ph]
Lepton Flavour Violation in SUSY-seesaw: an update
MSSM + three right-handed neutrinos + SUSY partners
SPS-4
David Hitlin INFN SuperB Review Nov. 12, 2007

23. t  lll - LFV chiral couplings
SuperB sensitivity to t  lll is an order of magnitude better than for t  mg : 2x10-10
Models predict a wide range of B(t  lll )/B( t  mg ):
If t  lll is seen, it can, using polarized t’s, also be the key to studying the chiral couplings of the LFV physics
David Hitlin INFN SuperB Review Nov. 12, 2007

24. Polarized t’s can probe the chiral structure of LFV (lll)
Flipping the helicity of the electron beam allows us to
ascertain the chiral structure of dimension 6 four fermion lepton flavor-violating interactions
Dassinger, Mannell, et al.
David Hitlin INFN SuperB Review Nov. 12, 2007 24

25. Polarization
Longitudinally polarizing one or both beams allows a sensitive search for T violation in t production and/or CP violation in t decay
Seeing either of these phenomena is a longshot, but one with a substantial payoff
Longitudinal polarization of the electron beam is straightforward (was routine in SLC operation)
Longitudinal polarization of the positron beam is an R&D project
Luminosity enhancement
t polarization
David Hitlin INFN SuperB Review Nov. 12, 2007

26. The SuperB design has a longitudinally polarized e- beam
Several techniques of achieving longitudinal e- polarization of >80% at the IP are discussed in the CDR (see later presentation)
Provides polarization in the 10 GeV CM region, not at lower ECM
Production of polarized positrons (~40%) is a substantial R&D project, and in fact, a potential area of synergy with ILC R&D
SuperB plans only a polarized e-, which yields most of the physics benefits
David Hitlin INFN SuperB Review Nov. 12, 2007

27. CP violation in t production and a t EDM
With a polarized electron beam, can define an azimuthal asymmetry in hadronic t decays sensitive to to a t EDM :
Summing over t+ and t- yields a true CP-odd observable
Sensitivity:
where
Bernabeu et al.
A three order of magnitude improvement over current bounds
David Hitlin INFN SuperB Review Nov. 12, 2007

28. CP Violation in t decay Unpolarized t’s
Measure B’s of t decays with two or more hadrons Interpretation of any observed CPV requires understanding of inelastic final state interactions
Measure CP or T-violating correlations in t+t- decays
Polarized t’s
Search for T-odd rotationally invariant products, e.g.
in t+ and t- decays such as
Search for T-odd correlation between t polarization and m polarization in decay
Sensitivity to asymmetries at the 10-3 level
David Hitlin INFN SuperB Review Nov. 12, 2007

29. Tau magnetic dipole moment
The polar angle distribution of t’s is sensitive to the t magnetic dipole moment
It is necessary to understand the reconstruction efficiency as a function of polar angle to the 10-3 level by use of
a control sample
This level of understanding can already be demonstrated with in BABAR data:
J.Bernabeu et.al hep-ph
With polarized e-, it is possible to separate the anomalous moment ff from the charge ff
BABAR 75
(Data/MC) inefficiency (%)
Polar Angle q (radians)
BABAR
Preliminary
Reconstruction inefficiency
(~1%) measurable with a 10% uncertainty
Goals are achievable
David Hitlin INFN SuperB Review Nov. 12, 2007

30. Extrapolated statistical errors on CP asymmetries
BABAR measurement errors
50 ab-1
Current precision
David Hitlin INFN SuperB Review Nov. 12, 2007

31. B g fK0 at 50/ab with present WA value
J/yK0
fK0
David Hitlin INFN SuperB Review Nov. 12, 2007

32. David Hitlin INFN SuperB Review Nov. 12, 2007
Conclusions
An excellent detector for SuperB can be constructed using an existing detector such as BABAR as a base
Improved hermiticity is of prime importance, as is improved vertex detection, better muon ID, a much higher bandwidth DAQ system, and an improved trigger
A polarized electron beam enables t EDM, CPV and anomalous moment measurements
Polarization experiments impose no new requirements on the detector
In fact, systematics due to detector inhomogeneity are reduced
There is, of course, overlap with the programs of LHC flavour experiments such as LHCb, but the e+e- environment makes possible a substantial number of unique and important physics objectives, especially in those areas most sensitive to new physics, such as LFV, FCNC, decays involving (multi) neutrals, mixing, …..
The achievable levels of sensitivity in rare B and t decays allow substantial coverage in the parameter space of new physics
High statistics flavour physics at an e+e- collider will likely provide information crucial to the understanding of new physics found at LHC
David Hitlin INFN SuperB Review Nov. 12, 2007