Physics reach of a Super B-Factory
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Transcript Physics reach of a Super B-Factory
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
-1
Integrated Luminosity (fb )
How high
the
luminosity?!?
PEP-II/Super-B
Data Sample
100,000
10,000
1,000
100
10
00
02
04
06
08
10
12
14
Year
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
Recoil physics is cleaner
BXln
Vcb
Vub
Inclusive lepton analysis
Single-B beams
Precision Measurement of the
sides of the Unitary Triangle
sstat
(2007)
%
sstat
(2011)
%
ssys
(2011)%
sth
(>2010) %
D(*,**)ln
0.4
0.1
1
1-2
b cln
1
0.5
0.5
5
buln
3
0.7
2.5
5
B Xuln
9
2
2.5
1-2
Vtd
DMd*
0.2
0.05
0.5
5
Vub,Vtd
Bn
CKM
Vcb
Vub
Analysis
5% on
Vub?
* DMd/DMs would be more interesting but not doable by Y(4S) SBF
Precise measurement of the
angles: impact of SUSY
Ratio of MSSM/SM
amplitudes
Ratio of
amplitudes in SM
MSSM phase
SM phase
r
r
r
Precision Measurement of the
angles : b
1
J/ y p 0
f K S0
D*+ D*-
pp
rp
0.1
J / y KS0
Sys err
0.01
Sys err
lepton tags
0.001
10
100
1000
10000
Integrated luminosity (/fb)
100000
(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
Current precision on ACP(B0p+p-) yields Isolating penguin pollution
s(sin2aeff) ~ 0.03 in 10 ab-1
with 2aeff = 2a + 2d
2d
f
requires measurement of
tagged B0 p 0p 0 and B 0 p 0p 0
decay branching fractions,
which can only be done at a B
Factory
L = 2 ab-1
L = 10 ab-1
f’
… but there is a 4-fold
ambiguity! (revert triangle
and fp-f)
2d (rad)
2d (rad)
Precision
Measurement of
angles : g
2ab-1, actual detector
r
sin2g
g
0.3
0.71 0.14
(58.5 7.4)o
A( B - D0 K - )
r
A( B - D0 K - )
0.2
0.70 0.26
(59.0 11.2)o
O (0.1)
0.1
unreliable
unreliable
2 A (B- D0+ K-) = A (B- D0 K-) + A (B- D0 K-)
Measure:
G(B- D+ K- ) =
G(B- D0 K- )
-
-
f -+ (g, Dd, r)
G(B D- K )
=
G(B- D0 K- )
f --
G(B+ D- K- )
=
G(B- D0 K- )
f
+
G(B+ D+ K- )
=
G(B- D0 K- )
f ++
• 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:
~ 0.03 with 2 ab-1
s(ACP)
Precision Measurement of the
angles : 2b+g
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(*)p, now extended to
B0D(*)r,a1,Ks
This reduces th. Error
Expected asymptotic error
s~0.05
W
B0
b
d
d
u
c
d
p+
b
D(*)-
d
W
d
c
u
d
D(*)+
p-
Expected Errors 1 year of SBF
s(sin2b)~0.008
s(sin2aeff )~0.032
s(BR(p0p0))~6%
s(g(DK))~2o
s(sin(2b+g))~0.05
Rare decays and New Physics:
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= 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
Super B-Factory % B-Factory
Beam
e+
e-
e-
e+
E(GeV)
8.0
3.5
9.0
3.1
#bunches
lifetime (min)
7000
800
7
5
Current (A)
10.3
23.5
b*(mm)
x=15/y=1.5
x=450/y=10
Emittance(nm)
x= 44/y=0.44
40/2.5
Beam spot (mm)
x= 81/y=0.8
x= 147/y=5
0.10
0.07
Tune shift
200
1.0
1.8
Normalized luminosity degradation factor
Boost optimization
B0 ® p + p -
high p lepton tag
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 10 36 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m
30
Q4
20
Close
Q1
10
+
e
Q2
Q5
X-ing
angle
Q1
Q1
e-
cm 0
Q1
-10
Q1
-20
Q4
Q5
Q2
-30
-7.5
-5
-2.5
0
m
2.5
5
7.5
3 1-J AN - 20 02
M. Sulliv a n
With increasing luminosity beam beam interactions increase wrt
syncrotron radiation/vacuum loss extrapolations from PEP very
rough
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.
Crucial point is the calorimeter (sensitivity to background &
p0p0 reconstruction).
Trigger rates:
Radiation resistant and fast smaller
Smaller detector higher magnetic field
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
IFR with same
design
New EMC –
Liquid Xe, YAP,
LSO?
DIRC
New tracker –
Two inner pixel
Layers
Thin double-sided
Si-strip arch layers
New DIRC(s) with
compact readout
Summary
Physics case for SuperBaBar : precise
measurements in the flavor sectors:
Design of SuperBFactory
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
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