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Physics Prospects of Super KEKB and Belle II. Kurtis Nishimura University of Hawaii (on behalf of the Belle II Collaboration) Lake Louise Winter Institute, 2011 February 24, 2011. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A A A.

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Physics prospects of super kekb and belle ii

Physics Prospects of Super KEKB and Belle II

Kurtis Nishimura

University of Hawaii

(on behalf of the Belle II Collaboration)

Lake Louise Winter Institute, 2011

February 24, 2011

TexPoint fonts used in EMF.

Read the TexPoint manual before you delete this box.: AAAAAAA


History of successes from b factories

History of Successes from B Factories

  • Belle and BaBar have made a wide variety of achievements over ~10 year running period:

    • CKM measurements of:

      • Matrix elements

      • Unitary triangle angles

      • CKM is correct to ~first order

    • Direct CP violation:

      • B  K ¼

    • New hadronic states:

      • X,Y,Z mesons

    • Rare probes of new physics:

      • b  s °

      • b  s

  • Belle II at SuperKEKB provides a unique opportunity to constrain and search for new physics at the intensity frontier, in a complimentary way to LHC.

Nishimura - Physics Prospects of Super KEKB / Belle II


Belle ii @ superkekb toward 50 ab 1

Belle II @ SuperKEKB: Toward 50 ab-1

  • Belle II / Super KEKB* timeline:

    • Expect to begin operation in 2014.

    • Collect ~50 ab-1 by 2020-2021.

  • Physics Prospects:

    • What can we do with 50 ab-1 of data?

      (…and what can we do along the way?)

    • How are super B factory measurements complementary to those at LHC?

  • Selected physics topics, examples of:

    • Modes with missing energy: B ¿º

    • Direct CP violation: B  K ¼

    • Mixing-induced CP violation: b  s °

    • Many more available at: http://belle2.kek.jp/physics.html & arXiv:1002.5012

*Details of SuperKEKB / Belle II detector covered in previous talk (H. Nakayama)

Nishimura - Physics Prospects of Super KEKB / Belle II


Benefits of e e environment

Benefits of e+e- Environment

(4.0 GeV)

(7.0 GeV)

  • At Belle II, B’s are produced by:

    • One B meson (“tag” B) can be reconstructed in a common decay.

      • Fully reconstructed: e.g., B  D(*)¼, B  D(*)½, …

      • Partially reconstructed: e.g., semileptonically

    • Allows determination of “signal” B flavor, charge, momentum.

      • Particles associated with “tag” B can be removed from event.

         Allows searches for modes with missing energy.

Nishimura - Physics Prospects of Super KEKB / Belle II


Missing energy modes b

Missing Energy Modes: B-¿ -º

  • Tension between the global CKM fit and :

Current world ave.

~2.8 ¾ discrepancy

Expectation from CKM fit

Example w/ semileptonic tag, 657M BB

PRD82:071101 (2010)

Bkg only.

Sig + bkg

Better measurement of B(B ¿º) may reveal source of the tension.

Tag-side information vital when ¸2 º’s in

final state! Signal is seen as zero excess EECL.

Nishimura - Physics Prospects of Super KEKB / Belle II


B at belle ii

B ¿º at Belle II

  • Belle II discovery region with 5 ab-1

  • Assumes improvements intheory values:

    • 5% |Vub| error

    • 5% fB error

5 ¾ discovery region

current 95% exclusion

  • Also sensitive to new physics:

    • In type-II Two-Higgs Doublet Model (THDM), the SM branching fraction of B-¿ -º is modified:

Nishimura - Physics Prospects of Super KEKB / Belle II


B at belle ii1

B ¿º at Belle II

  • Belle II discovery region with 50 ab-1

  • Assumes improvements intheory values:

    • 2.5% |Vub| error

    • 2.5% fB error

5 ¾ discovery region

current 95% exclusion

*Does not yet account for improvements in full-recon efficiency. Recently work suggests O(2x) improvements.

  • Also sensitive to new physics:

    • In type-II Two-Higgs Doublet Model (THDM), the SM branching fraction of B-¿ -ºis modified:

Nishimura - Physics Prospects of Super KEKB / Belle II


Direct cp violation b k

Direct CP Violation: B  K ¼

  • If the only diagrams are:

    then we expect ¢A= 0

    • Missing diagrams?

    • Hadronic interactions?

       These result in large theoretical uncertainty…

B  K ¼ w/ 535M BB

Nature 452, 332 (2008).

  • Puzzle of direct CP violation in K ¼:

    • Difference in DCPV in charged/neutral B decays:

Nishimura - Physics Prospects of Super KEKB / Belle II


Cpv in b k at belle ii

CPV in B  K ¼ at Belle II

Gronau, PLB627, 82 (2005)

  • Current situation:

*Slope determined by branching fractions & lifetimes, fairly precisely known.

  • However, we can compare to a model independent sum rule:

    • This rule is free of the previous theoretical complications.

    • Can be represented as a diagonal band:

Nishimura - Physics Prospects of Super KEKB / Belle II


Cpv in b k at belle ii1

CPV in B  K ¼ at Belle II

Gronau, PLB627, 82 (2005)

  • Current situation:

Shaded region is overlap of A(K0¼0) and A(K0¼+).

  • Benefits from:

  • Charged K/¼ ID (TOP counter)

  • ¼0°°detection (ECL)

  • KSvertexing eff. (increased SVD radius)

  • …and of course, statistics

 Belle II is especially well suited to measure the all neutral final state: K0¼0

  • However, we can compare to a model independent sum rule:

    • This rule is free of the previous theoretical complications.

    • Can be represented as a diagonal band:

Nishimura - Physics Prospects of Super KEKB / Belle II


Cpv in b k at belle ii2

CPV in B  K ¼ at Belle II

Gronau, PLB627, 82 (2005)

  • Current situation:

Shaded region is overlap of A(K0¼0) and A(K0¼+).

  • Benefits from:

  • Charged K/¼ ID (TOP counter)

  • ¼0°° detection (ECL)

  • KSvertexing eff. (increased SVD radius)

  • …and of course, statistics

Projected

w/ 50 ab-1

 Belle II is especially well suited to measure the all neutral final state: K0¼0

  • However, we can compare to a model independent sum rule:

    • This rule is free of the previous theoretical complications.

    • Can be represented as a diagonal band:

Nishimura - Physics Prospects of Super KEKB / Belle II


Mixing induced cp violation in b s

Mixing Induced CP Violation in b s °

: Allowed

: Suppressed by ms / mb

  • In SM, photon polarizations in b s ° depend on b flavor:

  • Presence of significant mixing-induced CP violation would indicate the presence of right handed currents and clear hints of new physics.

    • This type of new physics does not require a new phase.

Nishimura - Physics Prospects of Super KEKB / Belle II


Time dependent cpv in b s

Time Dependent CPV in b  s °

Belle preliminary, arXiv: 1012.0481

B Á K ° with 772M BB

  • A recent example:

    • Search for TCPV in B Á K °

    • Measurements are statistics limited…

      • Also the case for similar modes:B KS¼0°, B  K*°

Nishimura - Physics Prospects of Super KEKB / Belle II


Time dependent cpv in b s1

Time Dependent CPV in b  s °

  • Statistics limited for S(b  s °) in other modes

Nishimura - Physics Prospects of Super KEKB / Belle II


Time dependent cpv in b s2

Time Dependent CPV in b  s °

  • Example improvements in the error of S as a function of integrated luminosity for:

  • This sensitivity can help distinguish between models…

Nonresonant KS¼0°

Resonant K*0°

All KS¼0°

Belle II projected

  • Efficiency for KS¼+¼- improves with SVD radius.

Nishimura - Physics Prospects of Super KEKB / Belle II


Identifying np at belle ii

Identifying NP at Belle II

Projected with 5 ab-1

Belle II can identify the nature of NP, in some cases indistinguishable at LHC.

Randomly chosen parameter point

Current 99% CL on S(B ÁKS)

Nishimura - Physics Prospects of Super KEKB / Belle II


Summary

Summary

  • Belle II at SuperKEKB will enable a new generation of precision studies in flavor physics.

    • A number of unique opportunities to further constrain SM and search for new physics.

  • Significant opportunities both during data collection and with final dataset (50+ ab-1).

    • Only a short sampling of modes given here… for more information, see:

      • http://belle2.kek.jp/physics.html

      • Belle II Technical Design Report - arXiv:1011.0352

        Belle II and LHC experiments will be nicely complimentary.

Nishimura - Physics Prospects of Super KEKB / Belle II


Physics prospects of super kekb and belle ii

Nishimura - Physics Prospects of Super KEKB / Belle II


Missing energy modes b k

Missing Energy Modes: B  Kºº

BaBar analysis w/ 657M BB

PRD 82, 112002 (2010)

Current best upper limits by BaBar:

 Another mode with two neutrinos: well-suited for B-factory environment.

  • FCNC process:

    • Loops in penguin / box diagrams make B  Kºº sensitive to new physics.

    • SM prediction [Buchalla, PRD 63, 014015 (2001)]:

Nishimura - Physics Prospects of Super KEKB / Belle II


B k at belle

B  K(*)ºº at Belle

Nishimura - Physics Prospects of Super KEKB / Belle II


Physics prospects of super kekb and belle ii

Nishimura - Physics Prospects of Super KEKB / Belle II


Physics prospects of super kekb and belle ii

B  D*¿º

Nishimura - Physics Prospects of Super KEKB / Belle II


Ckm fitter

CKM Fitter

Nishimura - Physics Prospects of Super KEKB / Belle II


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