measurements of the unitarity triangle parameters at belle ii 名古屋大学 堀井泰之 1 b...
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Measurements of the unitarity triangle parameters at Belle II
名古屋大学 堀井泰之
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B ファクトリー物理勉強会 第 6 回ミーティング (2011.6.11)
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SuperKEKB
SuperKEKB
Energy (e-/e+) = 7.0/4.0 GeV
Our design value is on the U(4S) resonance. Data for other U resonances will also be taken.
Luminosity = 8.0 x 1035 /cm2s
40 times higher than 2.1 x 1034 /cm2s by KEKB. (Small beam size: x 20. Large beam current: x2.)
U(10860)
(8.0/3.5 GeV for KEKB.)
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Belle II detector
electron(7 GeV)
positron (4 GeV)
チェレンコフイメージ検出器による粒子識別性能の向上K± (p±) を 95% の効率で選ぶ時、
p± (K±) は 1% の確率でしか残らない。
シリコン検出器の外径拡大( 140 mm )による KS (p+p-) acceptance の向上
ピクセル検出器導入による崩壊点精度の向上( ~20 mm )
高いバックグラウンド環境に耐えられるように設計。それに加え、種々の性能向上。
LHCb に比べ、中性粒子を終状態に含むモードに強みを持つ。
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Measurements of the CKM parameters
Search for new physicsfrom measurementsof angles and sides of UT.
tension
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Measurement of f1
B0(cc)K0 B0(ss)K0
Standard Model:
Discrepancy in the results between B0(cc)K0 and B0(ss)K0
could be a signature of new physics.
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B(cc)K0Belle preliminary (Moriond 2011)using full U(4S) data (0.71 ab-1).
Consistent results for the four modes.
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B(cc)K0
sin2f1 (indirect CPV)
A (direct CPV)
Measured
Belle, 0.49 ab-1 0.642±0.031±0.017 0.018±0.021±0.014
Belle, 0.71 ab-1 0.668±0.023±0.013 0.007±0.016±0.013
BaBar, 0.42 ab-1 0.687±0.028±0.012-
0.024±0.020±0.016
Expected
Belle II, 5 ab-1 ±0.016 ±0.015
Belle II, 50 ab-1 ±0.012 ±0.013
O(0.01) precision at 50 ab-1.
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B(ss)K0
J/K0
fK0
50 ab−1
S(K0)=0.39 is assumed.
O(0.01) precision at 50 ab-1.Comparable to B(cc)K0.
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Note: tension in the CKM fit Tension between CKM fit and direct measurement of
BR(Btn):
Tension will be slightly loosened when we include new result on f1,while it will be still larger than 2.5s…
Direct measurement of Btn at Belle II will be important.
~2.8s discrepancy
ICHEP 2010
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Note: Btn at Belle II In Two-Higgs Doublet Model (THDM) Type II,
the branching ratio of Btn can be modified.
5 ab-1
assuming 5% errorsfor |Vub| and fB.
50 ab-1
assuming 2.5% errorsfor |Vub| and fB.
Figures: constrains onmH± and tanb at Belle II.
H-
Bmn is helicity-suppressed, and we need 1.6 ab-1 (4.3 ab-1) for 3s evidence (5s discovery).
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Note: BDtn at Belle II Also sensitive to charged Higgs.
H-
Exclusion boundaries
Uncertainty in BD semi-leptonic form factor.
Measurement of f3
Golden mode: B-DK- (and the conjugate)
Crucial parameters for extracting f3:
L. Wolfenstein,PRL 51, 1945
(1983)
rB ~ 0.1 (CKM x color-supp).
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Method of measuring f3
B-D0K-
B-D0K-_
D0f
D0f_
B- f K-f3
①
②
分岐比 ∝ |A(①) + A(②)|2
f3 測定法は、 f により分類できる。 GLW 法
f = CP 固有状態( K+K-, p+p-, KSp0, … )。
ADS 法 f = K+p-, K+p-p0 など。
Dalitz 法 f = KSp+p- など。 Dalitz 解析。
_f1, f2, f3 測定のためには、 | 振幅 |2 が f1, f2, f3 の関数になる崩壊を用いる。f3 測定は、 D0 と D0 の同じ終状態 f への崩壊を利用し行われる。
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GLW method
Relatively small contributions from CP-violating terms,since rB is small (~0.1). Non-zero ACP+ obtained.
Useful for extracting f3.
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ADS method
Well-balanced |amplitudes|.
First evidence of the signal obtained.(At rB=0.1, RADS is in 0.002-0.025.)
Sensitivity for f3 via GLW+ADSis 15° at 1 ab-1 and 3° at 50 ab-1.
f = K+p-
f = K+p-
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Dalitz method
Previous measurement: Modeling of amplitudes on Dalitz plane.(Especially strong phase for the D decays.)
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Dalitz method Belle preliminary (Moriond 2011).
Precision of ci, si will be improved by BESIII measurements.
Expected precision for f3 at 50 ab-1 is 2°.
Consistent with CKM fitw/o direct measurement:f3 = 67.2° ± 3.9°.
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D0-D0 mixing D0-D0 mixing is the largest theoretical uncertainty in the
extraction of f3. However, it can be safely neglected at the current
precision: df3~10°. The effect will be relatively larger at Belle II, while it can be
explicitly included in the extraction of f3.
_
_
J. P. Silva and A. Soffer, PRD61, 112001 (2000).Y. Grossman, A Soffer, and J. Zupan, PRD72, 031501(R).
50 ab-1 50 ab-1
Current contours Current contoursPrecision at 50 ab-1
a b
K-p+ K+p-
K-p0 K+p0
Note: Kp puzzleIf the only diagrams are a and b, we expect
However, significant difference is obtained.
Missing diagrams?Large theoretical uncertainty…
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BKp w/ 0.5 ab-1
Nature 452, 332 (2008)
DCPV due to Vub.
Note: DCPV for BKp at Belle II We can compare to a model-independent sum
rule:
Current measurement larger error for ACP
K0p050 ab-1
assuming current central value
Can be represented as diagonal band(slope precisely known from B and lifetimes):
measu
red
measu
red
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ed
expect
ed
sum
rule
sum
rule
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Summary SuperKEKB
40 times higher luminosity of 8.0 x 1035 /cm2s. Will reach 50 ab-1 by the end of 2021.
Belle II Conservatively designed to cope with high background. Improvements in several aspects: vertex, KS acceptance,
PID, … Examples of physics at SuperKEKB/Belle II
Measurement of f1(eff) from B0(cc)K0 and B0(ss)K0.(Relation to the tension for Btn. Note on BDtn.)
Measurement of f3 from the tree BDK (GLW, ADS, Dalitz).(Relation to D0-mixing and direct CPV in BKp.)
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SuperKEKB Collider
TiN coated beam pipewith antechambers
Replace short dipoles with longer ones (LER).
Redesign the lattices of HER & LER to reduce the emittance.
e+Smaller asymmetry 8 / 3.5 GeV 7 / 4 GeV
e-
Damping ring
Belle II
L = 8 x1035 cm-2 s-1
sx~10mm, sy~60nm
Larger crossing angle 2f = 22 mrad 83 mradfor separated final-focus magnets.
Small beam sizes
Approved in 2010.
e-: 2.6 Ae+: 3.6 A
High currents
Vertex Detector
Belle
1st lyr.
2nd lyr.3rd lyr.
4th lyr.
4lyr. Si strip 2lyr. pixel(DEPFET) + 4lyr. Si strip
6th lyr.
5th lyr.4th lyr.
3rd lyr.
2nd lyr.1st
lyr.
Pixel: r=14,22mmSi strip:r=38,80,115,140mm
Si strippix
el
Improve decay-time precisionand acceptance (KS’s).
Belle II
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Aerogel radiator
Hamamatsu HAPD+ new ASIC
Cherenkov photon200mm
n~1.05
Endcap PID: Aerogel RICH (ARICH)
Barrel PID: Time of Propagation Counter (TOP)
Quartz radiatorFocusing mirror
Hamamatsu MCP-PMT (measure t, x and y)
TOP
n1 n2
Multiple aerogel layerswith different indices
sq(1p.e.) = 14.4 mradNpe ~ 9.6sq(track) = 4.8 mrad
Completely different from PID at Belle,with better K/p separation, more tolerance for BG, and less material.
Particle Identification System at Belle II
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Other Upgrades for Belle II
Belle
Belle II
Drift chamber: smaller cells
Calorimeter: new readout system with waveform sampling (x1/7 BG reduction)
Silicon vertex detector: new readout chip (APV25) shorter integration time (800 ns50 ns)
KL/Muon detector RPCScintillator+MPPC
Better performance against neutron BG
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Physics at SuperKEKB/Belle II
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A benefit to use
One B meson (“tag” side) can be reconstructed in a common decay.Flavor, charge, and momentum of the other B can be determined.
Also possible to partially reconstruct (semileptonically, …).
Effective for the modesincluding missing energy.Missing
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B-D(*)K-, DKSp+p- Dalitz Amplitude of B±DK± process can be expressed as
Procedure of analysis:1. Background fractions are determined by 2-D UML fit for
DE and Mbc.
2. Fit is performed to m± (Dalitz plane).
Amplitude of DKSp+p- decaydetermined from Dalitz plot of large continuum data(Flavor is tagged by soft-pion charge in D*±Dp±
soft).Isobar-model assumption with BW for resonances.
Ratio of magnitudesof interfering amplitudes.
A. Poluektov et al., PRD 81, 112002 (2010)
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B-D(*)K- Dalitz, Result Using the background fractions, Dalitz plane is
fittedwith the parameters x± = r±cos(±f3+d) and y± = r±sin(±f3+d).
Combining the results for BD(*)K, we obtain
Model-independent
analysis will be applied for 772M
BB.
A. Poluektov et al., PRD 81, 112002 (2010)
657 M BB