1 Trees, penguins and boxes at LHCb Prospects for CP violation measurements at LHCb Tristan du Pree (Nikhef) On behalf of the LHCb collaboration 14 th Lomonosov conference Aug 2009, Moscow ? To: LHCb

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 2 B-physics Study CKM-matrix CPV at BaBar B 0 →J/ψK s Rare B-decays at LHCb: See (previous) talk by N. Serra BR(B + → τν) BR’s and CPV Δt (ps) asymmetry

3 Example CP violation 2 amplitudes Relative weak phase φ w –Flips sign under CP Relative strong phase δ –Does not flip sign under CP |A tot | 2 = |A 1 +A 2 | 2 Need both nonzero δ and φ w for CP asymmetry: Im Re CP Im Re A1A1 A2A2

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 4 Current status CKM Unitarity: 4 free parameters Of which one complex phase  Perform different measurements to overconstrain CKM matrix Status: SM CKM mechanism explanation of CP violation –No significant inconsistencies Some interesting deviations –β eff (penguins) –|V ub |(B + → τν) vs β –“Kπ puzzle” –Φ s (related to β s ) Big uncertainty in γ  Stronger constraints needed! –To overconstrain CKM matrix and discover New Physics Subject today

5 LHCb CP violation research: γ with trees γ with loops Φ s Φ s with penguins σ bb ~ 500 μb (10% B s ) ‘1 year’ = 2.0 fb -1  Produce O(10 11 ) B s per year  Expect to reconstruct: O(100k) B s → J/ψφ per year Forward arm spectrometer ~20mx10mx10m L = (2-5) x cm -2 s -1

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 6 CP violation at LHCb γ with time dependent osc B s → D s K B → D*π γ with direct CPV B → DK (glw) B → DK (ads) More bodies γ with loops B → hh Φ s B s → J/ψφ Φ s with penguins B s → φφ Brown = box Green = tree Black = penguin Advantages of LHCb Number of B s ’s Proper time and mass resolution Particle ID

7 The B s mixing phase β s equivalent of β in B d system + “Фs”“Фs” βsβs If ΔΓ s =0: (in general ΔΓ s ≠0) ? To: LHCb

8 Time dependent CPV Final state f is a ccss CP-eigenstate CP Amplitude: sin(Φ s ) DsK: σ t ~ 40fs Time res. important __ LHCb:

9 CP-even vs CP-odd Blue: total Green: CP-even Red: CP-odd L=1 BsBs φ J/ψ L=0,2 If ΔΓ s =0: (simplified expression, in general ΔΓ s ≠0) A CP ~ |A even | 2 sinΦ s sinΔm s t −|A odd | 2 sinΦ s sinΔm s t Initial B s : J=0 Different final spin states  Different angular momenta L in final states  Different CP: factor (-1) L  CP-even and CP-odd opposite proper time behaviour

10 Angular analysis Blue: total Green: CP-even Red: CP-odd 4 particles: 3 decay angles Angles of daughter particles in rest frame parents Angular distribution: information about spin polarizations  CP states different angular distributions  Perform angular analysis to separate CP-even & CP-odd If ΔΓ s =0: (simplified expression, in general ΔΓ s ≠0) A CP ~ |A even | 2 sinΦ s sinΔm s t (1 + cos 2 θ)/2 -|A odd | 2 sinΦ s sinΔm s t (1 - cos 2 θ)

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 11 LHCb sensitivity: σ(Φ s ) Simultaneous likelihood analysis in mass, time, angles and tagging flavour Using mass sideband to model background Green = signal Red = background Blue = sum Expectation from toy MC 2.0 fb -1 : σ(Φ s ) ~ 1.8º

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 12 Sensitivity: σ(Φ s ) 0.2 fb -1 (8 TeV): σ LHCb (Φ s ) < σ TeVatron (Φ s ) 2.0 fb -1 (14 TeV): If Φ TeVatron = Φ true : LHCb 5σ discovery!

13 B s → φφ Compare: phase(tree) & phase(penguin) B s → φφ angular analysis à la B s → J/ψφ σ(Φ φφ )=4.6º σ(sin(Φ φKs ))=0.23

14 γ with trees (1) B s → D s K: time-dependent oscillation CP With 2.0fb -1 : σ( γ +Φ s )=9º-12º Amplitude: δ s ±( γ +Φ s )

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 15 γ with trees (2) Decay time independent CPV in B → DK ~V cb V us * D 0 ~V ub V cs * D 0 Sum of amplitudes leads to CPV –Relative strong phase δ –Relative weak phase γ  For interference: need a common final D 0 &D 0 state Theoretically clean measurement of γ V ub

16 γ with trees (2) Decay time independent CPV GLW: Choose CP-even final state –D 0 → K + K -, D 0 → π + π - –D CP is CP-even D 0 -D 0 mixture Rates → δ+ γ Rates (CP-conjugated) → δ- γ  The combination gives two solutions of γ Combination of all methods after 2.0 fb -1 : σ( γ ) = 4-5º PID by RICH important γ γ Without RICH With RICH

17 γ with loops B → hh Interfere b → u tree diagram with penguins: V ub * Particle ID crucial Mass resolution RICH (like previous page)

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 18 LHCb with 2 fb -1 γ with time dependent osc B s → D s K B → D*π γ with direct CPV B → DK (glw) B → DK (ads) More bodies γ with loops B → hh σ( γ -Φ s ) = 9º-12º σ( γ ) = 4-5° σ( γ ) = 7° σ(Φ s ) = 2.8 ° -3.4 ° Φ s B s → J/ψφ Φ s with penguins B s → φφ σ(Φ s ) = 1.8º σ(Φ φφ ) = 4.6 º Advantages of LHCb Number of B s ’s Proper time and mass resolution Particle ID Brown = box Green = tree Black = penguin

24 Aug th Lomonosov Conf., Moscow Tristan du Pree Nikhef 19 Conclusions CKM model successful in describing CP violation –…but γ and β s poorly constrained –…and inconsistencies at the horizon? Many different methods to study diagrams –Standard model diagrams (trees) –Possible new physics contributions (boxes, penguins) LHCb will drastically improve the sensitivity to the CKM angles γ and β s

Something new in the box of B s → J/ψφ?

BACK-UP

22 Unitarity Triangle Constraints following from unitarity of CKM matrix –Three complex numbers add up to zero Performing different measurements, overconstrain 4 free parameters in CKM matrix –To test consistency of CKM model –Inconsistency (e.g. triangle doesn’t close) → new physics

23 UT after 5 years of LHCb in case of no new physics

24 Current status UT experimental constraints on unitary CKM matrix CKM mechanism explanation of CPV –No significant inconsistencies Some interesting deviations –β eff (penguins) –B → τν vs β –“Kπ puzzle” –β s Biggest uncertainty in γ  Stronger constraints needed! –To constrain CKM & discover NP Subject today

25 Present status β s Left: Indirect (UT s ) Right: Direct (B s → J/ψφ TeVatron) βsβs UT s 2.0 fb -1 LHCB: σ(β s ) ~ 0.9° p-value(SM): 3.4% (~2.1σ) (ρ s,η s ) ≈ -λ 2 (ρ,η) _ _ __

26 LHC 27 km Proton-proton √s = 14 TeV? Re-start this fall LHCb L = (2-5)x10 32 cm -2 s -1 σ bb ~500μb (10% B s ) ‘1 year’ = 2.0fb -1 Produce O(10 11 ) B s per y. Expect to reconstruct: O(100k) B s → J/ψφ per y.

27 Present status Ф s Indirect (CKM fit) Direct (B s → J/ψφ TeVatron) ФsФs 2.0 fb -1 LHCB: σ(Ф s ) ~ 1.8° p-value(SM): 3.4% (~2.1σ)