Belle II: Motivation, Status, and Prospects Ryosuke Itoh KEK on - - PowerPoint PPT Presentation

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Belle II: Motivation, Status, and Prospects Ryosuke Itoh KEK on - - PowerPoint PPT Presentation

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Belle II: Motivation, Status, and Prospects Ryosuke Itoh KEK on behalf of Belle II collaboration XIIth International Conference on Heavy Quark & Leptons 2014 25-29 August 2014, Schloss Waldthausen, Mainz, Germany 1 R.Itoh, HQL2014

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Belle II:

Motivation, Status, and Prospects

Ryosuke Itoh KEK

XIIth International Conference on Heavy Quark & Leptons 2014 25-29 August 2014, Schloss Waldthausen, Mainz, Germany

  • n behalf of Belle II collaboration
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Outline

  • 1. Motivation of Belle II experiment
  • 2. SuperKEKB and Belle II
  • 3. Construction Status and Plan
  • 4. Search for New Physics at Belle II
  • 5. Collaboration with Theorists
  • 6. Summary
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  • Up to now, there is no symptom of New Physics(NP) observed

in LHC experiments. There is a possibility that the scale of NP is even more than 10 TeV, which is out of reach by LHC.

  • The indirect search for NP at Belle II, a new generation B-factory

where there is no limit in the search energy, will be more important.

  • However, the effect of NP in the indirect processes is expected

to be tiny, and it has not been observed by Belle/BaBar so far, except for several “anomolous” measurements:

* ACP(B0K+p-)  ACP(B+K+p0) (5.6s discrepancy), * Unexpectedly large D0-D0 mixing (although SM pred. has large uncertainties) * Br(BD(*)tn) : ~5s discrepancy from SM pred.

  • To go beyond, more precise measurements in much higher statistics
  • f events is required.

Accelerator upgrade to achieve > x40 higher luminosity. SuperKEKB/Belle II

=

  • 1. Motivation of Belle II Experiment
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Standard Model New Physics ex.1 ex.2

How do we search for New Physics in Belle II?

  • Search for the “shift” from SM prediction caused by an existence
  • f a new particle in quantum effect.

In order to search for NP, the measurement has to be compared with the Standard Model prediction in a high precision. We need both of * High precision experimental measurement * High precision theory prediction of Standard Model

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  • 2. SuperKEKB and Belle II
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The SuperKEKB accelerator

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The Belle II detector

  • High granularity “pixelized” sensors  to be tolerable for high rate

* Improved vertex detector with DEPFET Pixel sensors + DSSD * Improved particle ID devices (TOP, ARICH)

  • High bandwidth DAQ (>30GB/sec data flow @30kHz, >1MB/event)
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Vertex Detector : Pixel detector + Silicon strip detector

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Particle ID : TOP + ARICH

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FE dig FE dig FE dig FE dig FE dig tx tx tx tx tx rx rx rx rx R/O PC R/O PC R/O PC R/O PC Event Builder 1 ~300 COPPERs ~0.5M chan. HLT farms ~O(10) units of ~400 cores/unit ~30 R/O PCs Near detector E-hut DAQ server room Rocket IO

  • ver fiber

CDC SVD PID ECL KLM Event Builder 2 PXD FE dig PXD readout box HLT distributor reco rder reco rder reco rder reco rder RAID ~10 units ...... ..... DATCON

Belle2link

Express Reco Feed back to PXD R/O 30kHz 100kB/ev 10kHz 200kB/ev 30kHz 1MB/ev 10kHz 100kB/ev 10kHz 300kB/ev = 3GB/s

1/3 rate reduction 1/10 size reduction

DAQ : PXD data reduction by HLT feed-back

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  • 3. Construction Status and Plan

Wire-stringing of CDC completed KLM installation almost completed TOP optics assembly in progress HLT 1st unit ready

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  • 4. Search for New Physics at Belle II
  • Examples of “Golden modes”

a) CPV in tree level and penguin decays

  • sin 2f1(charm) vs. sin 2f1(strange)

b) CPV in radiative decays

  • sin 2f1 in BKsp0g

c) Missing Energy

  • pure leptonic decay of B : Bln (l=e,m,t)
  • BD(*)tn

d) Lepton Flavor Violation(LFV)

  • tmg, tmmm

e) CPV in D0-D0 mixing

  • Ultra-precise measurement of unitarity triangle
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bb→cccs tree diagram bb→sqqc loop diagram

019 . 682 . φ 2 sin 03 . 64 . φ 2 sin

W.A 1 W.A 1

     

s c c q sq

1) CPV in bs transition

possible contribution of new particle * Deviation ~0.8s

d(sin2f1 (sqq))= ~0.012@50ab-1 SM predicts the same value at a precision of ~1%.

Current measurement

Prospect in Belle II

c

* Some of systematics are cancelled by taking the difference between measurements for ccs and sqq.

~

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bb→scγR: right handed photon b→sγL: lefu handed photon

 

         

b s

m m S 2 φ 2 sin

1 SM

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2) CPV in B⁰→K⁰Sπ⁰γ (b→sγ)

SM:

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a) Pure leptonic decay of B meson SM :

δ(Br) ~ 5% @ 50ab⁻¹

Prospect in Belle II

HFAG13

3) Missing Energy

Br(Btn)SM = (1.11±0.28)10-4 Br(Btn)SM = (1.14±0.22)10-4

(2HDM)

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b) BD(*)tn

  • World Average is shifted

~ 5s from SM prediction!

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Constraint on Charged Higgs mass by Btn

3σ

  • Excl. at

2σ 5σ

Btn

Now (Belle+BaBar) * 2HDM (Type II) cannot explain the difference between Dtn and D*tn in BaBar data..... 2HDM (Type II) BaBar

* Detailed study with precise measurements at Belle II is required.

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4) Lepton Flavor Violation (LFV) : tmg, tmmm

Theoretically very clean test of Standard Model SM: NP: Br ~ 10-25 Prospect in Belle II < ~10-9 (Bmg) < ~10-10 (Bmmm)

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5) CP Violation in D0-D0 mixing

SM (+NP): + Long distance

HFAG2013 Belle II 50ab-1

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Physics Reach of Belle II and the LHCb upgrade

Belle II/LHCb

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Expected CKM constraint with 50/ab

sr = 3.4 % sh = 1.7%

* Adjusted central values used. (except Dmd, Dms, and eK) * Measurement errors with 50/ab : arXiv1002.5012 * Lattice parameters : PBF numbers

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  • 5. Collaboration with Theorists
  • Since there is no clear scenario of NP discovery in Belle II,

we need to seek for every possible way for NP search.

  • A closer collaboration with theorists is essential to have an
  • ptimized strategy of NP search.

* “NP-Japan group” was formed in 2012. * “Belle II Theory interface Platform (B2TiP)” has been initiated in 2014.

  • The purpose of these groups is to provide a framework to

work both theorists and Belle II experimentalists together closely.

  • The strategy includes the global fit activity to combine

multiple NP-sensitive measurements in order to maximize the sensitivity to NP.

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https://belle2.cc.kek.jp/~twiki/bin/view/Public/B2TIP

8 working groups + New physics working group

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  • 6. Summary
  • Belle II is a new generation B-factory experiment for the

hunt of New Physics in rare B/D/t decays.

  • The construction of SuperKEKB and Belle II is on-going

aiming at the start of physics run in 2017.

  • A wide variety of physics program is there utilizing an

enormous event statistics obtained with a 40 times higher

  • luminosity. It is complementary to the one of LHCb.
  • A close collaboration with theorists has been initiated to
  • ptimize the strategy for the New Physics search at Belle II.

Stay Tuned!

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Backup Slides

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From Belle to Belle II

  • We had been studying B meson decays in the previous

Belle experiment (B-factory exp.@KEK) for more than 10 years.

  • The main purpose of the Belle experiment is to establish the

CP violation in B meson decays within the framework of Standard Model, as predicted by Kobayashi-Maskawa.

  • > It was confirmed by Belle + BaBar and

brought Novel prize to them.

  • The purpose of Belle II upgraded from Belle is the experimental

search for the signature of New Physics in B, D and t decays. <- Indirect search for NP in “quantum effect”

  • No guiding theory for promising NP search. Need a careful

study of “subtle” shift from Standard Model(SM) in various measurements.

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0.001 0.01 0.1 1 10 Energy scale of NP Coupling to NP LHC Tevatron 100 TeV Belle II

Comparison of NP sensitivity by LHC and Belle II experiments

Belle

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