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Physics reach of a Super B-Factory
Riccardo FacciniUniversita’ “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
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 (~0.2%) Advantages:
All the remaining tracks come from the other B possibility to apply partial reconstruction (e.g.
BD* (D0)sin a clean way
Heavily used in sys error reduction in the following
Physics with single B-beams
?
Recoil physics is cleaner
Inclusive lepton analysis
Single-B beams
Vub
Vcb
BXl
Precision Measurement of the sides of the Unitary Triangle
CKM Analysis stat
(2007)%
stat
(2011)%
sys
(2011)%
th
(>2010) %
Vcb D(*,**)l 0.4 0.1 1 1-2
b cl 1 0.5 0.5 5
Vub bul 3 0.7 2.5 5
B Xul 9 2 2.5 1-2
Vtd Md* 0.2 0.05 0.5 5
Vub,Vtd B 5% on Vub?
Md/Ms would be more interesting but not doable by Y(4S) SBF
r r r
Precise measurement of the angles: impact of SUSY
MSSM phase
SM phase
Ratio of amplitudes in SM
Ratio of MSSM/SM amplitudes
Precision Measurement of the angles :
0.001
0.01
0.1
1
10 100 1000 10000 100000
I nt egr ated lum inosi ty ( /f b)
0/ SJ Ky
rppp
0 /J y p0SKf
* *D D+ -
0/ SJ Ky
rppp
* *D D+ -
0/J y p0SKf
Sys err
Sys err lepton tags
(stat err. ~70% larger)
Only J/Ks 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 :
2
’
(sin2eff) ~ .03 in 10 ab-1with 2eff = 2
Current precision on ACP(B0+-) yields Isolating penguin pollution requires measurement of tagged and decay branching fractions, which can only be done at a B Factory
0 0 0B 0 0 0B
L = 10 ab-1
(rad)(rad)
L = 2 ab-1
… but there is a 4-fold ambiguity! (revert triangle and )
)1.0(
)(
)(
0
0
O
KDBA
KDBAr
2ab-1, actual detectorr sin2
0.3
0.2
0.1 unreliable unreliable
• Crucially depends on r (breaks down for r < 0.1?)
• 8-fold ambiguity spoils the extraction of
• But ACP = 2r sin sin is accessible: (ACP) ~ 0.03 with 2 ab-1
= f --++ (, , r)
)()(
0
++
KDB KDB
)()(
0
--
KDB KDB
)()(
0
--
KDB KDB
)()(
0
++
KDB KDB
= f ----
= f ++--
= f ++++
Measure:
2 A (B- D0+ K
-) = A (B- D0 K-) + A (B- D0 K-)
Precision Measurement of angles :
Precision Measurement of the angles :
Interference between Vcb and Vub diagrams in bcud transitions exploited to measure sin2
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(*),a1,Ks This reduces th. Error Expected asymptotic error
~0.05b
c
W d
u
d dD
bu
W
cD(d
d d
Expected Errors 1 year of SBF
(sin2)~0.008
(sin2eff)~0.032 (BR(00))~6%
((DK))~2o
(sin())~0.05
Rare decays and New Physics:
bs single-B beams reduce the model dependence and allow time dependent measurements. B.F., CP asymmetries sensitive to NP.
Bdirect CP asymmetry and Br()/Br(K*) 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
Blrelative ratio of the channels (l= vs l=)
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 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
Super B-Factory % B-Factory
Beam e+ e- e- e+
E(GeV) 8.0 3.5 9.0 3.1
#bunches 7000 800
lifetime (min) 7 5 200
Current (A) 10.3 23.5 1.0 1.8
*(mm) x=15/y=1.5 x=450/y=10
Emittance(nm)
x= 44/y=0.44 40/2.5
Beam spot (m)
x= 81/y=0.8 x= 147/y=5
Tune shift 0.10 0.07
Boost optimization
0 high lepton tagB pp p+ -®
Nor
mal
ized
lum
inos
ity
degr
adat
ion
fact
or
Lifetime details Luminosity: interacting particles get
lost Vacuum: beam-gas scattering Touschek: intra-beam scattering Beam-beam: optimize tune shifts Dynamic aperture: due to beta
functions
Injection details
Interaction region
PEP-II 1036 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m
30
20
10
0
-10
-20
-30
cm
-7.5 -5 -2.5 0 2.5 5 7.5m 31-JAN-2002
M. Sullivan
Q1
Q1Q1
Q1
Q2
Q4
Q5Q2
Q4Q5 e+
e-
With increasing luminosity beam beam interactions increase wrt syncrotron radiation/vacuum loss extrapolations from PEP very rough
X-ing angle
Close Q1
Super BaBar: detector issues
Background considerations will drive detector design. The vacuum/luminosity background should be ~600 larger than PEP, but other sources should take place. Radiation resistant and fast smaller Smaller detector higher magnetic field
Crucial point is the calorimeter (sensitivity to background & reconstruction).
Trigger rates: LV1 ~ 100KHz ; 5GB/s LV2 ~ 6Khz; 300 MB/s
Computing ~50 times more challenging than BaBar Will have to wait for better machine design before
being able to make detector strawman
Calorimeter design choises
A potential upgrade path from BABAR to SuperBABAR
DIRC
IFR with same design
New EMC –Liquid Xe, YAP,
LSO?
New tracker –Two inner pixelLayers
Thin double-sided Si-strip arch layers
New DIRC(s) with compact readout
Summary Physics case for SuperBaBar : precise
measurements in the flavor sectors: Sensitivity to new physics :
Probe CP violation parameters of new physics Resolve ambiguities in NP zoology
Reduce systematics (e+e- machines more suited: single beam approach)
Select high number of events in penguin dominated processes Workshop at SLAC 20-22 March 2003
Design of SuperBFactory First set of parameters released in May Workshop in February 2003
Design of SuperBaBar Waiting for physics case and B factory Working group within BaBar will report by fall 2003