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
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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
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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
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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
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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
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High precision B physics involves reducing the
systematic errors
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?
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. BD p 
(D0)psp ) in a clean way
Heavily used in sys error reduction in the following
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Recoil physics is cleaner
BXln
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
buln
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
Bn
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(B0p+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 fp-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
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Interference between Vcb and Vub diagrams in
bcud 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 B0D(*)p, now extended to
B0D(*)r,a1,Ks
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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
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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:
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bsg single-B beams reduce the model dependence
and allow time dependent measurements. B.F., CP
asymmetries sensitive to NP.
Br/wg direct CP asymmetry and Br(rg)/Br(K*g)
sensitive to MSSM
BXsll CP asymmetry small in SM and large in MSSM
Bll BF are very small, but could become non
negligible with NP contributions
Bln 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
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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
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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
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Background considerations will drive detector design. The
vacuum/luminosity background should be ~600 larger than
PEP, but other sources should take place.
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Crucial point is the calorimeter (sensitivity to background &
p0p0 reconstruction).
Trigger rates:
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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
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Physics case for SuperBaBar : precise
measurements in the flavor sectors:
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Design of SuperBFactory
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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
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Waiting for physics case and B factory
Working group within BaBar will report by fall 2003