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Transcript of Hints for new physics from radiative/electroweak B decays ligeti/talks/hints.pdf Hints for new...

  • Hints for new physics from radiative / electroweak B decays

    Zoltan Ligeti

    Hints for new physics in flavor decays KEK, 20-21 March 2009

    • Introduction • b→ sγ: Rate, asymmetries, inclusive & exclusive • b→ s`+`−: Optimal observables to constrain short distance physics

    Small and large q2 regions; sensitivity to shape function, connections to |Vub|

    • b→ sνν̄: The theoretically cleanest of all • Conclusions

  • Preliminaries / Disclaimers

    • In a previous millenium (i.e., mid-1990’s), I did not care too much about what had been measured (my apologies to CLEO!), only what might be measured one day

    Z. Ligeti — p. 1

  • Preliminaries / Disclaimers

    • In a previous millenium (i.e., mid-1990’s), I did not care too much about what had been measured (my apologies to CLEO!), only what might be measured one day

    It was fun, sometimes I miss those days... sounding like a really old person :-)

    Z. Ligeti — p. 1

  • Preliminaries / Disclaimers

    • In a previous millenium (i.e., mid-1990’s), I did not care too much about what had been measured (my apologies to CLEO!), only what might be measured one day

    It was fun, sometimes I miss those days... sounding like a really old person :-)

    • So I will not talk specifically about any of the ∼2σ hints available today... I think it’s more interesting to explore what’s possible with ∼100 times more data

    (These measurements are of course important; chance of >3σ before upgrade?)

    Z. Ligeti — p. 1

  • Preliminaries / Disclaimers

    • In a previous millenium (i.e., mid-1990’s), I did not care too much about what had been measured (my apologies to CLEO!), only what might be measured one day

    It was fun, sometimes I miss those days... sounding like a really old person :-)

    • So I will not talk specifically about any of the ∼2σ hints available today... I think it’s more interesting to explore what’s possible with ∼100 times more data

    (These measurements are of course important; chance of >3σ before upgrade?)

    • Existing Super-B studies tend to concentrate on observables in exclusive modes, so I’ll focus on inclusive (K∗`+`− also possible at LHCb)

    Z. Ligeti — p. 1

  • Preliminaries / Disclaimers

    • In a previous millenium (i.e., mid-1990’s), I did not care too much about what had been measured (my apologies to CLEO!), only what might be measured one day

    It was fun, sometimes I miss those days... sounding like a really old person :-)

    • So I will not talk specifically about any of the ∼2σ hints available today... I think it’s more interesting to explore what’s possible with ∼100 times more data

    (These measurements are of course important; chance of >3σ before upgrade?)

    • Existing Super-B studies tend to concentrate on observables in exclusive modes, so I’ll focus on inclusive (K∗`+`− also possible at LHCb)

    • In my opinion, building a Super-B-factory is clearly justified 2–3σ effects may be temporary, so let’s concentrate on finding the best combina- tions of theoretical cleanliness and experimental feasibility

    Z. Ligeti — p. 1

  • Main reason (for me) to continue

    3 φ

    3 φ

    2 φ

    2 φ

    dm∆ Kε

    sm∆ & dm∆

    SLub V

    ν τub V

    1 φsin 2

    (excl. at CL > 0.95)

    < 0 1

    φsol. w/ cos 2

    excluded at C L > 0.95

    2 φ

    1 φ

    3 φ

    ρ −1.0 −0.5 0.0 0.5 1.0 1.5 2.0

    η

    −1.5

    −1.0

    −0.5

    0.0

    0.5

    1.0

    1.5 excluded area has CL > 0.95

    Moriond 09

    CKM f i t t e r

    dh 0.0 0.2 0.4 0.6 0.8 1.0

    dσ 0.0

    0.5

    1.0

    1.5

    2.0

    2.5

    3.0

    0.0

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1.0 1-CL

    Moriond 09

    CKM f i t t e r

    ντ →w/o B

    • Very impressive accomplishments • Level of agreement between various

    measurements often misinterpreted

    Parameterize: M12 = MSM12 (1 + hd e2iσd)

    Most loop-mediated transitions may have 10–20% NP contributions w/o fine tuning

    Z. Ligeti — p. 2

  • The rare B decay landscape

    • Important probes of new physics (a crude guide, ` = e or µ) Decay ∼SM rate present status expected

    B → Xsγ 3.2× 10−4 (3.52± 0.25)× 10−4 4% B → τν 1× 10−4 (1.73± 0.35)× 10−4 5% B → Xsνν̄ 3× 10−5 < 6.4× 10−4 only Kνν̄ ? B → Xs`+`− 6× 10−6 (4.5± 1.0)× 10−6 6% Bs → τ+τ− 1× 10−6 < few % Υ(5S) run ? B → Xs τ+τ− 5× 10−7 < few % ?

    B → µν 4× 10−7 < 1.3× 10−6 6% B → τ+τ− 5× 10−8 < 4.1× 10−3 O(10−4) Bs → µ+µ− 3× 10−9 < 5× 10−8 LHCb B → µ+µ− 1× 10−10 < 1.5× 10−8 LHCb

    • Many interesting modes will first be seen at super-B (or LHCb) Maintain ability for inclusive studies as much as possible (smaller theory errors)

    • Some of the theoretically cleanest modes (ν, τ , inclusive) only possible at e+e−

    Z. Ligeti — p. 3

  • B → Xsγ

  • Inclusive B → Xsγ calculations

    • One (if not “the”) most elaborate SM calculations Constrains many models: 2HDM, SUSY, LRSM, etc.

    • NNLO practically completed [Misiak et al., hep-ph/0609232] 4-loop running, 3-loop matching and matrix elements

    Scale dependencies significantly reduced ⇒

    • B(B → Xsγ) ∣∣ Eγ>1.6GeV

    = (3.15± 0.23)× 10−4

    measurement: (3.52± 0.25)× 10−4

    • O(104) diagrams, e.g.: b s

    c

    c

    γ

    Z. Ligeti — p. 4

  • The B → Xsγ photon spectrum

    • World average: B(B → Xsγ) = (3.52± 0.25)10−4 Could have easily shown deviations from SM

    • Exp. cut: Eγ >∼ 1.9 GeV ⇒ mB − 2Ecutγ ∼ 1.5 GeV Three cases: 1) Λ ∼ mB − 2Eγ � mB Three cases: 2) Λ� mB − 2Eγ � mB Three cases: 3) Λ� mB − 2Eγ ∼ mB Neither 1) nor 2) is appropriate

    • Can combine 1–2 w/o expanding Λ/(mB − 2Eγ) [ZL, Stewart, Tackmann, 0807.1926]

    9 models with the same 0th, 1st, 2nd moments =⇒ Including all NNLL corrections, smaller shape func- tion uncertainty for Eγ

  • Photon polarization in B → Xsγ

    • Is B → Xsγ due to O7 ∼ s̄ σµνFµν(mbPR+msPL)b or s̄ σµνFµν(mbPL+msPR)b? SM: In ms → 0 limit, γ must be left-handed to conserve Jz O7 ∼ s̄ (mbFLµν +msFRµν) b , therefore b→ sLγL dominates

    � ����������

    Inclusive B → Xsγ γ sb

    Assumption: 2-body decay Does not apply for b→ sγg

    Exclusive B → K∗γ γ KB *

    ... quark model (sL implies JK ∗

    z = −1) ... higher K∗ Fock states

    • Had been expected to give SK∗γ = −2 (ms/mb) sin 2φ1 [Atwood, Gronau, Soni] Γ[B0(t)→ K∗γ]− Γ[B0(t)→ K∗γ] Γ[B0(t)→ K∗γ] + Γ[B0(t)→ K∗γ]

    = SK∗γ sin(∆mt)− CK∗γ cos(∆mt)

    • Data: SK∗γ = −0.16±0.22 — both the measurement and the theory can progress Z. Ligeti — p. 6

  • Right-handed photons in the SM

    • Dominant source of “wrong-helicity” photons in the SM is O2 Equal b→ sγL, sγR rates at O(αs); calculated to O(α2sβ0)

    Inclusively only rates are calculable: Γ(brem)22 /Γ0 ' 0.025

    Suggests: A(b→ sγR)/A(b→ sγL) ∼ √

    0.025/2 = 0.11

    [Grinstein, Grossman, ZL, Pirjol]

    b s

    c O2

    • B → K∗γ: At leading order in ΛQCD/mb, wrong helicity amplitude vanishes Subleading order: no longer vanishes [Grinstein, Grossman, ZL, Pirjol]

    Order of magnitude: A(B 0 → K0∗γR)

    A(B0 → K0∗γL) = O

    „ C2

    3C7

    ΛQCD

    mb

    « ∼ 0.1

    Some additional suppression expected, but I don’t find

  • Other observables

    • Direct CP asymmetry: AB→Xsγ = −0.012± 0.028 AB→Xd+sγ = −0.011± 0.012 AB→K∗γ = −0.010± 0.028

    Theoretical predictions < 0.01, except AB→ργ which is larger

    • Isospin asymmetry: it seems to me that theoretical uncertainties would make it hard to argue for new physics

    • If these observables don’t show NP, I doubt higher K states, etc., could

    Z. Ligeti — p. 8

  • B → Xs`+`−

  • Inclusive b→ s`+`− calculations • Complementary to B → Xsγ • Subtleties in power counting (as in K → πe+e−) C9(mb) ∼ C9(mW) + (. . .)

    C2(mW)

    αs(mW)

     1− » αs(mb)

    αs(mW)

    –(···)ff Scale & scheme dependence cancellation tricky

    • NNLL: 2-loop matching, 2- and 3-loop running NNLL: 2-loop matrix elements

    B(B→Xs`+`−) ∣∣ 1

  • The q2 spectrum in B → Xs`+`−

    • Rate depends (mostly) on O7 =mb s̄σµνeFµνPRb,

    O9 = e2(s̄γµPLb)(¯̀γµ`),

    O10 = e2(s̄γµPLb)(¯̀γµγ5`)

    Theory most precise for 1 GeV2 < q2 < 6 GeV2−→ • NNLL b→ s`+`− perturbative calculations

    Introduce Ceff7,9 — complex with usual definition 0 5 10 15 20

    0

    1

    2

    3

    4

    [Ghinculov, Hurth, Isidori, Yao]

    • Nonpertu