Physics reach of a Super B-Factory Riccardo Faccini
Universita’ “La Sapienza” e INFN Roma
CSNI , 4 Febbraio 2003
Physics reach of a Super B-Factory Riccardo Faccini
Universita’ “La Sapienza” e INFN Roma
CSNI , 4 Febbraio 2003
Motivations
PEP-II/BABAR and KEK-B/Belle have provided the first evidence that the CKM phase is indeed the source of CP violation in B meson (and, by extension) K meson weak decays
Since the matter-antimatter asymmetry of the universe cannot be accounted for by Standard Model CP violation, we had a reasonable expectation that the Standard Model would fail this unique test
The Standard Model passed the test
The unitarity triangle construction is self-consistent
It is now time to test the higher orders (loops) and this requires a luminosity of 1036 cm-2s-1
Overconstrain the unitary triangles with much smaller errors
Study decay distributions of loop dominated, rare, decays
How high the luminosity?!?
today SuperBFactory (SBF)
New physics and flavor physics
CP violation is an excellent probe of new physics:
The CKM mechanism has a single source of CPV and makes quantitative predictions
New sources of flavor and CP violation can induce large deviations from the Standard Model predictions, many of which are not obscured by hadronic uncertainties
Henceforth in this discussion, I will use the supersymmetric SM :The supersymmetric SM has 124 independent parameters, 44 of which are CP-violating
SBF can probe the CP violating part of Susy and resolve the ambiguities in the new particles zoology
Physics with single B-beams
? High precision B physics involves reducing the systematic errors
It can be achieved at expense of stat error.
Fully reconstruct one B and look at the recoil in an inclusive way 4 M Bs /ab-1 (e~0.2%)
Advantages:
All the remaining tracks come from the other B
possibility to apply partial reconstruction (e.g. BD*p (D0)psp ) in a clean way
Heavily used in sys error reduction in the following
Precision Measurement of the sides of the Unitary Triangle
5 0.5 0.05 0.2 DMd* Vtd
5 0.5 0.5 1 b cl 9 3 0.4 sstat
(2007)% Vub,Vtd Vub Vcb CKM 1-2 2.5 2 B Xuln 5% on Vub? 0.7 0.1 sstat
(2011)% 2.5 1 ssys
(2011)% B 5 bul 1-2 D(*,**)ln sth
(>2010) % Analysis * DMd/DMs would be more interesting but not doable by Y(4S) SBF
Precise measurement of the angles: impact of SUSY
r r r MSSM phase SM phase Ratio of amplitudes in SM Ratio of MSSM/SM amplitudes
Precision Measurement of the angles : b
Sys err Sys err lepton tags
(stat err. ~70% larger) Only J/YKs will be syst. Limited, but one can use only the cleaner tags to reduce the error. All comparisons still stat. Limited.
Precision Measurement of the angles : a
2d f f’ s(sin2aeff) ~ 0.03 in 10 ab-1
with 2aeff = 2a + 2d Current precision on ACP(B0p+p-) yields Isolating penguin pollution requires measurement of tagged and decay branching fractions, which can only be done at a B Factory L = 10 ab-1 2d (rad) 2d (rad) L = 2 ab-1 … but there is a 4-fold ambiguity! (revert triangle and fp-f)
Precision Measurement of angles : g
2ab-1, actual detector unreliable unreliable 0.1 (59.0 11.2)o 0.70 0.26 0.2 (58.5 7.4)o 0.71 0.14 0.3 g sin2g r Crucially depends on r (breaks down for r < 0.1?)
8-fold ambiguity spoils the extraction of g
But ACP = 2r sin Dd sin g is accessible: s(ACP) ~ 0.03 with 2 ab-1 = f -+ (g, Dd, r) ) ( ) ( 0 + ® G ® G - - - + K D B K D B ) ( ) ( 0 - ® G ® G - - - - K D B K D B ) ( ) ( 0 - ® G ® G - - - + K D B K D B ) ( ) ( 0 + ® G ® G - - - - K D B K D B = f -- = f +- = f ++ Measure: 2 A (B- D0+ K-) = A (B- D0 K-) + A (B- D0 K-)
Precision Measurement of the angles : 2b+g
b c W d p+ u B0 d d D(*)- b u W p- c D(*)+ d d d Interference between Vcb and Vub diagrams in bcud transitions exploited to measure sin2b+g
The biggest limitation comes from the knowledge of the amplitude of oscillations (~0.02). Theoretical uncertainty ~30%
Initial idea involved only B0D(*), now extended to B0D(*)r,a1,Ks
This reduces th. Error
Expected asymptotic error
s~0.05
bsg single-B beams reduce the model dependence and allow time dependent measurements. B.F., CP asymmetries sensitive to NP.
Br/wg direct CP asymmetry and Br(rg)/Br(K*g) sensitive to MSSM
BXsll CP asymmetry small in SM and large in MSSM
Bll BF are very small, but could become non negligible with NP contributions
Bln relative ratio of the channels (l=t vs l=m)
CPV in exclusive radiative decays
Probe SUSY in K*ll
M2ll (GeV2)
Comparison on rare decays
Super-BF: design considerations
Change boost to optimize cost/physics
Smaller lifetimes continuous injection
More and shorter bunches
X-ing angle ~ 1.5 mrad (impact on backgrounds)
Redesign HER lattice
Focussing Magnets closer to I.P. to get smaller b functions
Vacuum system will have to dissipate 16 KW/m of syncrotron radiation
RF system, same as B-Factory but scaled up 1 O.o.M.
Cost of power, 100 times higher than now
Planned workshops:
February 2003: SBF Workshop
October 14-17, 2003 SLAC: ICFA Workshop on e+e- Factories
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