Recent topics in heavy-quark flavour physics

Recent topics in heavy-quark flavour physics Martin Jung IFICFA mini-workshop, Valencia, Spain 23rd of November 2012

Outline Introduction Status of the SM Flavour Sector B D ( ) τν in the A2HDM CPV in charm Conclusions

Motivation Fundamental Question(s): What is matter made of and how does it interact? Historically: From early guesses... Source: http://www.formatplus.ch/store/ images/4elemente 005.jpg

Motivation Fundamental Question(s): What is matter made of and how does it interact? Historically: From early guesses...... to useful concepts: Source: http://www.formatplus.ch/store/ images/4elemente 005.jpg Source: http://csi.chemie.tu-darmstadt.de/ ak/immel/misc/pse/pse.jpg

Last century (basically) Atoms consist of electrons and a nucleus. Nuclei consist of neutrons and protons. A neutron can decay into a proton, electron, and an (anti-)neutrino. Neutrons and protons are built from up and down quarks (for the moment). The first family of matter particles! But there is more ( Who ordered that? ): Muon discovered 1936 in cosmic rays e ν u, d 1950 discovery of strange particles, violating universality: Concept of strangeness Eightfold way, concept of quarks Cabibbo: generalized universality, Jµ w = cos θjµ S=0 + sin θjµ S=1

Our preliminary answer Today: (At least) three copies of the first family Interactions Forces mediated by particles: Gauge Bosons Best known: Photon (γ) Moreover: Gluons mediate the strong, W ±, Z the weak force. Finally: The famous Higgs(-Kibble-Englert- Brout)-particle, still to be discovered. Source: Wikipedia Flavour physics: Characteristics of and transitions between the families

Weak Decays In the SM, weak decays (of quarks)... are the only source of flavour changing transitions! are the only source of CP violation! are weak due to suppression by M W,Z. Flavour changing transitions are charged: No FCNC (at tree level) GIM mechanism They take the form L cc ū /W + V CKM d + h.c., with flavour structure V ud V us V ub d ūv CKM d = ( ū c t ) V cd V cs V cb s. V td V ts V tb b V ij coupling constants for transitions j i.

The Cabibbo-Kobayashi-Maskawa matrix V CKM is a unitary matrix, V CKM V CKM = V CKM V CKM = diag(1, 1, 1), with a hierarchical structure: V ud V us V ub V cd V cs V cb 1 V td V ts V tb This is reflected in the Wolfenstein parametrization: 1 λ2 2 λ Aλ 3 ( ρ i η) V CKM = λ 1 λ2 2 Aλ 2 + O(λ 4 ), Aλ 3 (1 ρ i η) Aλ 2 1 with λ V us sin θ C 0.22 as expansion parameter. 1 Source: http://cyclotron.aps.org/weblectures/apr03/kirkby/real/slides/img016.gif

The Unitarity Triangle Unitarity implies: 0 = (Vub V ud + Vcb V cd + Vtb td)/ Vcb V cd ( ρ + i η) 1 + (1 ρ i η) This can be visualized as triangle in the complex plane: Measurements restrict the apex in all kinds of ways...

A closer look Tension(s) in direct vs indirect determination of sin 2β: Main issue: B τν Tree-level process However: sensitive to NP WA: sin 2β 0 @ 2.8σ Additionally: V B τν ub Vub sl sin 2β Vub inclusive vs exclusive Vub sl ɛ K largish (input-dependent) Increased interest in sources for sin 2β

A closer look Tension(s) in direct vs indirect determination of sin 2β: Main issue: B τν Tree-level process However: sensitive to NP New Belle result, < 2σ! Additionally: V B τν ub Vub sl sin 2β Vub inclusive vs exclusive Vub sl ɛ K largish (input-dependent) Increased interest in sources for sin 2β

Why New Physics? The SM works fine - far better than expected! Up to now, no direct measurement contradicts it. However...

Why New Physics? The SM works fine - far better than expected! Up to now, no direct measurement contradicts it. However... The Baryon-asymmetry of the universe cannot be explained. Only O(%) of the observed energy density of the universe explained dark matter and energy. Hierarchy problem: why is M H /M Planck 10 17? Masses and mixing angles only accomodated for in the SM, they are not explained (Anthropic principle?). New Physics needed (at best at the TeV scale)!

NP in mixing I Three parameters in B q mixing: M q 2 M q 12, Γ q 2 Γ q 12 cos φ q, a q SL = Γq 12 M q 12 sin φ q NP in Γ 12 severely constrained Not considered here [Dighe et al. 10,Bauer/Dunn, Oh/Tandean, Dorsner et al., Bobeth/Haisch 11] Parametrization for NP only in M 12 : M q 12 = qm SM 12. Development for B s -mixing: [Lenz et al. 10, 12] 2010: Apparent large effects, φ s φ SM s Driven by φ s from CDF,D0 and a SL from D0 Both could be fitted by d,s

NP in mixing I Three parameters in B q mixing: M q 2 M q 12, Γ q 2 Γ q 12 cos φ q, a q SL = Γq 12 M q 12 sin φ q NP in Γ 12 severely constrained Not considered here [Dighe et al. 10,Bauer/Dunn, Oh/Tandean, Dorsner et al., Bobeth/Haisch 11] Parametrization for NP only in M 12 : M q 12 = qm SM 12. Development for B s -mixing: [Lenz et al. 10, 12] 2012: LHCb (and CDF) results fix φ s, Γ Best fit basically SM, large effects excluded φ s and a SL not compatible

NP in mixing II Less change in B d mixing, 2012 results: [Lenz et al. 12] a SL marginally compatible p-value d = 1 (SM): 3σ However: Largely due to B τν Not a mixing observable

NP in mixing II Even newer 2012 results (incl. B τν Belle ): [CKMfitter] asl d compatible (new measurements agree with SM) p-value d = 1 (SM): 1.6σ

NP in mixing II Even newer 2012 results (incl. B τν Belle ): [CKMfitter] asl d compatible (new measurements agree with SM) p-value d = 1 (SM): 1.6σ Alltogether: Worse fit than 2010 with only NP in M 12 Semileptonic asymmetry in conflict with φ d,s Independent check important! Additional NP in Γ q 12 possible, but difficult Interpretation of sin 2β as NP in mixing challenged

More indications of NP in decay: Why 2HDM? Most importantly: BaBar measurements of B D ( ) τν 3.4σ disagreement with the SM (!) A charged Higgs affects these decays! Electroweak symmetry breaking mechanism unknown yet: 1HDM minimal and elegant, but unlikely (SUSY,GUTs,... ) 2HDM: ρ-parameter implies doublets next-to-minimal low-energy limit of more complete NP models Model-independent element simple structure, but interesting phenomenology affects the aforementioned tensions Model-independent analysis: Too many parameters in general

General 2HDM: Lots of 2HDMs... L q Y = Q L (Γ 1φ 1 + Γ 2 φ 2 ) d R + Q L ( 1 φ 1 + 2 φ2 ) u R + h.c. Γ i, i : Independent 3 3 coupling matrices Flavour problem: generic couplings imply huge NP scale Most common solution: Applying a discrete Z 2 symmetry Cannot explain B τν, B D ( ) τν! Lots of other models: Type III [Cheng/Sher 87] BGL [Branco et al. 96, Ferreira/Silva 10] 2HDM with MFV [D Ambrosio et al. 02,Buras et al. 10]...

The Aligned two-higgs-doublet model Alignment condition: Γ 2 = ξ d e iθ Γ 1, 2 = ξ u e iθ 1 leads to [Pich/Tuzón 09] L q 2 Y,H = ± v H+ (x)ū(x) [ ς d VM d P R ς u M uv ] P L d(x) + h.c. with complex, observable parameters ς u,d,l, implying: No FCNCs at tree-level New sources for CP violation Only three complex new parameters (unlike Type III) Z 2 models recovered for special values of ς i s Radiative corrections symmetry-protected, of MFV-type (Cvetic et al. 98, Braeuninger et al. 10, MJ/Pich/Tuzón 10) Recently: Proposals towards UV-completion (Medeiros Varzielas 11, Serôdio 11)

Leptonic decays within the A2HDM In the SM... [MJ/Pich/Tuzón 10] are suppressed by m 2 l have only f B as hadronic input measure V ub In the A2HDM... W ± is replaced by H ± still involve only f B are suppressed by m 2 l, but BR(B τν) A2HDM BR(B τν) SM = 1 ub 2, ij M2 ij M 2 H ± ς l (ς um i + ς d m j ) m i + m j O(1) effects possible, can enhance BR(B τν)!

Semileptonic decays in the A2HDM More complicated: form factors Without helicity suppression in SM Smaller influence of H ± Influence tiny for l = e, µ information on form factor A2HDM influence: f 0 (q 2 ) f 0 (q 2 ) [MJ/Pich/Tuzón 10,Celis/Li/MJ/Pich 12] ( q 2 ) 1 + M B M D ) 2 δ cb (B D) δ cb = (M B M D ) 2 ςl (ς um c ς d m b ) MH 2 m ± b m c ) H 0t (q 2 ) H 0t (q 2 ) (1 q2 MB 2 cb (B D )

Confronting model and data R(D) Br( B Dτ ν τ ) Br( B Dl ν l ) R(D ) Br( B D τ ν τ ) Br( B D l ν l ) Rules out SM and Type II 2HDM Ok with A2HDM, also B τν Problem: ς u ςl very large Conflict with D ± (s) lν Different scenarios: A2HDM without R(D ) NP in b cτν transitions only Analyze predictions for further observables avg = 0.438 ± 0.056 ( 2σ from SM) avg = 0.354 ± 0.026 (> 3σ from SM)

Predictions for observables in B D ( ) τν decays Main questions: Differentiation of the scenarios possible (w/o R(D ))? Can we decide scalar NP vs. other structures? Consider additional observables: Forward-backward asymmetry τ-spin asymmetry Longitudinal polarization fraction in B D Additionally, the q 2 distributions can be studied 0.8 B D ΤΝΤ RD q2 0.6 0.4 0.2 0.0 4 5 6 7 8 9 10

Why is charm physics important? Historically: NP itself, predicted by GIM established in November Revolution Nowadays?

Why is charm physics important? Historically: NP itself, predicted by GIM established in November Revolution Nowadays? Charm is still unique! Position in the spectrum Only up-type quark with oscillating mesons tops don t hadronize, π 0 is its own anti-particle Experimentally accessible Well suited for lattice-studies Sensitive to New Physics...

Why is charm so difficult? Main problem: Λ QCD m c Λ QCD Basically our usual methods don t work here: Operator-product expansion (OPE) in Λ QCD /m c questionable Energetic decay products e.g. in D PP have E < 1 GeV Considering m c 0 does not work either Three-body MEs still extremely hard on the lattice Also: SU(3) severely broken Methods to determine matrix elements urgently needed!

a CP Big news in November 2011 from LHCb: a CP = a K + K CP a π+ π CP = ( 0.82 ± 0.21 ± 0.11)% February: CDF measures a CP = ( 0.62 ± 0.21 ± 0.10)% ICHEP 12: Belle measures a CP = ( 0.87 ± 0.41 ± 0.06)% Larger than expected before in the SM! (but see [Golden/Grinstein 92] ) Theoretically (next slide): a CP = acp dir + t /τaind CP Basically a measurement of direct CP-asymmetries

CPV in charm decays Three sources for CPV: in decay, mixing, and their interference All of these effects are tiny in the D-system! Furthermore: a mix CP a CP (f ) a dir CP + a mix CP + a int CP [Grossman et al. 06] and aint CP are universal, together denoted aind CP How large can we expect acp dir to be (naively tiny)? QCD fact.: few 0.01% (enhancement possible [Brod et al. 11] ) A(D 0 P + P ) = 2VcsV us A s + Vcb V uba b = 2A 0 (1 + r CKM r/2e iθ e iγ ) a dir CP r } CKM sin γ {{} 0.2% }{{} 0.9 }{{} r? Both r and sin θ were expected to be small Large strong phase ( sin θ 1) plausible r O(1) gives acp dir = few 0.1% sin θ }{{} [ 1,1]

How to decide SM vs. NP? As shown, the SM might accommodate the measurement Several NP scenarios allow for enhanced CPV [Isidori et al., Bigi et al., Hochberg/Nir 11,Giudice et al., Altmannshofer et al.,hilller et al. 12,... ] Inclusion of more modes necessary for a decision One option: symmetry methods ( ) Using exact symmetry limit is futile BR(D 0 K + K ) BR(D 0 π + π ) 2.8 U-spin breaking seems huge, but might be moderate: [Savage 91,Hiller/MJ/Schacht 12, Feldmann et al. 12,Brod et al 12] Takes form (1 + x) 2 /(1 x) 2, equals 2.8 for x 25% U-spin: fits D 0 h + h, but connects only a few modes Extension to SU(3) [Pirtskhalava/Uttayarat 12,Hiller/MJ/Schacht]

What can we do with this? Older works...... consider only U-spin [Feldmann et al., Brod et al. 12]... reduce breaking to lowest representations [Pirtskhalava/Uttayarat 12]... consider breaking in an ad-hoc way [Bhattacharya et al. 12] Generalization important However: General fits are very difficult Questions we want to address: [Hiller/MJ/Schacht 12] Can the full dataset D PP be described with reasonable SU(3) breaking? What are minimal scenarios to explain the data? How large the penguin enhancement has to be? Can we differentiate between different NP scenarios?

Quantifying SU(3) breaking Quantifying SU(3) breaking non-trivial. Here: 1. Maximum of normalized SU(3)-breaking ME (δ X ) Ignores suppression by Clebsch-Gordan coefficients 2. Maximum of normalized SU(3)-breaking amplitude (δ X ) Ignores possible cancellations New: Include all MEs(!) New: Include all data 0.5 Classify all solutions SU(3) breaking 20 40% ok Minimal solutions : need at least two O(ɛ) MEs need at least one ME from 0.1 higher representations 0.1 0.2 0.3 0.4 0.5 X 0.4 0.3 0.2 X

Quantifying penguin enhancement Analogously for penguins: 1. δ 3 max. normalized ME r CKM 2. δ 3 max. amplitude r CKM Earlier analyses: δ 3 3 Here: this (already huge) value only marginally allowed SM questioned even stronger 3 15 10 5 0 0 10 20 30 40 50 3 Reasons? Not only a CP! Other CPA s with largish c.v s (D 0 K S K S, D s π + K S, K + π 0 ) Together gain significance Without these, we confirm [Feldmann et al.,brod et al. 12] 3 4 3 2 1 0 0 1 2 3 4 3 68 C.L. 95 C.L.

SM still prevails Conclusions Interesting measurements with τ s, NP in decay? For NP in mixing, then only A SL remains, Γ NP d?? More measurements necessary! Semileptonic decays rule out SM and Type II 2HDM A2HDM ok, but conflict in global fit Various scenarios can be distinguished with new observables Direct CP violation in charm very exciting First unbiased, comprehensive analysis of D PP Description possible with reasonable SU(3) breaking Full fit requires even larger penguins SM questioned Higher representations necessary More data will help to distinguish different scenarios