Rare decays in the beauty, charm and strange sector

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1 Rare decays in the beauty, charm and strange sector Marcin Chrzaszcz FPCP, Hyderabad July / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 1/26 26

2 Outline 1. Beauty decays Λ b Λµµ B s K µµ B (s) eµ B K eµ. 2. Charm decays Λ c pµµ D hhµµ 3. Strange decays K S µµ Σ pµµ 2 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 2/26 26

3 Why rare decays? The SM allows only charged interactions to change flavour. Other interactions are flavour conserving. One can escape this constraint and produce b s and b d at loop level. These kinds of processes are suppressed in the SM Rare decays. New Physics can enter in the loops. 3 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 3/26 26

4 detector - tracking Int. J. Mod. Phys. A3 (215) Excellent Impact Parameter (IP) resolution (2 µm). Identify secondary vertices from heavy flavour decays Proper time resolution 4 5 fs. Good separation of primary and secondary vertices. Excellent momentum (δp/p.5 1.%) and inv. mass resolution. Low combinatorial background. 4 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 4/26 26

5 detector - PID Int. J. Mod. Phys. A3 (215) Excellent Muon identification ϵ µ µ 97%, ϵ π µ 1 3% Good K π separation via RICH detectors, ϵ K K 95%, ϵ π K 5%. Reject peaking backgrounds. High trigger efficiencies, low momentum thresholds. B J/ψX: Trigger 9%. 4 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 4/26 26

6 Rare beauty decays b sll family B K µµ Bs ϕµµ Λ b pkµµ LUV: R K, R K b sγ family B J/ψγ B Kππγ b dll family B ππµµ Bs K µµ Λ b pπµµ Too many results to be covered in one talk! Please see A. Oyanguren s talk for more! Purely leptonic family B ll LFV: B ll LFV in τ 5 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 5/26 26

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8 Λ b Λµµ -PAPER b sµµ in baryon sector. Because of spin 1/2 nature of the baryon there the system has to be described by 5 angles: Impossible to perform a likelihood fit. Need to use moments: M i = 3 32π 2 34 i=1 K i (q 2 )f( Ω )d Ω ẑ =ˆp { b } ŷ =ˆn ˆp b ẑ` ` =ˆp { b } ` ` ŷ` ` =ˆn ˆp { b } ` ` ẑ ŷ ŷ` ` b rest-frame ˆx ˆn b rest-frame ` ` ˆx, ˆx` ` ˆp { b } ` ` ˆx` ` ˆp {lab} b In total we have 34 observables! b ŷ` ` ẑ` ` ŷ b rest-frame ẑ p rest-frame ẑ p b b ŷ ˆx ẑ { } = ˆp { } ` ` 7 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 7/26 26

9 Λ b Λµµ -PAPER Update with 5 fb events observed at high q 2. Angular efficiency modelled in 6D. The results: 8 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 8/26 26

10 b d transitions ) The b d is further suppressed by V td / V ts B O(1 8 ). Already lots of results in Run1: Candidates / ( 3 MeV/c B π + µ + µ B K µ + µ + B D µ + ν,+,+ - B ρ µ + µ - Bs f µ + µ Combinatorial m(π + µ + µ ) (MeV/c ) [JHEP 1 (215) 34] ) 2 Events/(2 MeV/c Bs π + B π M(π + π µ + µ ) [GeV/c ] - π - π µ + µ + B K*(892) Bs + η' µ - µ Combinatorial Total fit - µ - µ µ + - µ [PHYS. LETT. B743 (215) 46] Candidates per 63 MeV/c Data Signal and bkg Λ b pπµµ Combinatorial Part reco m pπµµ / (MeV/c ) The ratio between the b s and b d can be used to determine some CKM elements: B(B πµµ) B(B Kµµ) V td/v ts =.2 ±.2 Large improvements expected in Run2. [JHEP 4 (217) 29] 9 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 9/26 26

11 B s K µµ arxiv:: fb 1 of data! 7 Analysis in 4 bins of NN 6 Data Fit response. 5 Bs K * µ + µ B K Signal yield determined from a µ 4 µ Λb simultaneous fit to the NN response bins. Normalized to B K J/ψ Comb. bkg. First evidence with 3.4 σ The measured branching fraction: ) Candidates / ( 1. MeV/c 2 pk µ + µ m(k π + µ + µ ) [MeV/c 2 ] B(B s K µµ) = (2.9 ± 1.(stat) ±.2(syst) ±.3(norm)) 1 8 For now consistent with SM predictions arxiv: / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 1/26 26

12 B s K µµ arxiv:: fb 1 of data! 3 Analysis in 4 bins of NN 25 Data Fit response. 2 Bs K * µ + µ B K Signal yield determined from a * µ + µ 15 Λb Comb. bkg. simultaneous fit to the NN 1 response bins. Normalized to B K 5 J/ψ. First evidence with 3.4 σ The measured branching fraction: ) Candidates / ( 1. MeV/c 2 pk µ + µ m(k π + µ + µ ) [MeV/c 2 ] B(B s K µµ) = (2.9 ± 1.(stat) ±.2(syst) ±.3(norm)) 1 8 For now consistent with SM predictions arxiv: / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 1/26 26

13 Lepton Flavour/Number Violation Lepton Flavour Violation(LFV): After µ was discovered it was logical to think of it as an excited e. Expected: B(µ eγ) 1 4 Unless another ν, in intermediate vector boson loop cancels. I.I.Rabi: Who ordered that? Up to this day charged LFV is being searched for in various decay modes. LFV was already found in neutrino sector. Anomalies may suggest connections between LUV and LFV. ( ) B(B Keµ) RK ( ).23 B(B Kµτ) RK.23 B(B s eµ) ( ) 1 B(B s µµ).1 RK.23 arxiv:: B(B s τµ) ( ) 1 B(B s µµ) 4 RK / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 11/26 26

14 ) ) B (s) eµ [JHEP 183 (218) 78] Need to deal with bremsstrahlung: different efficiency and mass shapes. Fit performed separately in bremsstrahlung categories. Primary background: B hh: ) Candidates / ( 1 MeV/c 2 Pull Data Total + ' B(s) h h Combinatorial B π e + ν m [MeV/c 2 µ + µ ] Estimated with the data driven method to be < 6 events. Candidates / ( 1 MeV/c 2 Candidates / ( 1 MeV/c Simulation m e ± µ [MeV/c 2 ] m e ± µ [MeV/c 2 ] ± Simulation ± 12 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 12/26 26

15 B (s) eµ With 3 fb 1 data. Fit the m eµ mass and calculate CL s. B(B e ± µ ) < 1.3(1.) 1 8 Candidates/(5 MeV/c 2 ) [JHEP 183 (218) 78].7 BDT 1. Data Total Combinatorial - Λb pµ ν - B π µ + ν B e ± s µ B e ± µ m e ± µ [MeV/c 2 ] ± ± ± CL s 1 CL s BF(B e ± µ ) ± BF(Bs e ± µ ) ± B(B s e ± µ ) < 6.3(5.4) 1 9 B(B s e ± µ ) < 7.2(6.) 1 9 if light eigenstate dominates if heavy eigenstate dominates 13 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 13/26 26

16 B K eµ Fit to M bc : M bc = (E beam ) 2 (p B ) 2 [Belle, arxiv:: ] No statistically significant events observed, upper limits set The best UL but order of magnitude above the LUV model predictions. 14 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 14/26 26

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18 Λ c pµµ [Phys. Rev D ] SM predictions: O(1 8 ) Long distance effects: O(1 6 ) Previous measurement done by Babar: Br(Λ + c pµ + µ ) < at 9% CL analysis with 3 fb 1 16 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 16/26 26

19 Λ c pµµ [PHYS. REV. D 97, 9111 (218)] Blind analysis with the normalization to the Λ c pϕ(µµ). BDT to reduce combinatorial background. The dominant background: Λ c pππ: 2. ± 1.1 events Candidates / (7 MeV/c 2 ) m(pµ + µ ) [MeV/c 2 ] Analysis performed in 3 mass windows: ϕ region: m µµ [985, 155] MeV/c 2 ω region: m µµ [759, 85] MeV/c 2 nonresonant: rest of phase-space. Candidates / (7 MeV/c 2 ) Candidates / (7 MeV/c 2 ) Candidates / (7 MeV/c 2 ) a) nonresonant b) φ region c) ω region m(p µ + µ ) [MeV/c 2 ] m(pµ + µ ) [MeV/c 2 ] 17 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 17/26 26

20 Λ c pµµ [PHYS. REV. D 97, 9111 (218)] It s the first observation of Λ c pµµ in the ω region, with 5. σ significance. The corresponding branching fraction reads: B(Λ c pω) = (9.4 ± 3.2 ± 1. ± 2.) 1 4 No significant excess observed in the nonresonant region: B(Λ c pµµ) < 7.7(9.6) 1 8 Candidates / (1 MeV/c 2 ) CL s m(µ + µ ) [MeV/c 2 ] observed expected ± 1 σ ± 2 σ Improving BaBar result by 3 orders of magnitude! B(Λ pµ + µ c ) [1-8 ] 18 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 18/26 26

21 D hhµµ [PHYS. REV. LETT. 119, (217)] Z µ + D c ū W + u q h + D q ū h µ c ū W + First observation with 2 fb 1 of data! Dominated by long distance contributions. Normalized to D Kπ[µµ] ω/ρ has measured the branching fractions: B(D ππµµ) = (9.64 ±.48 ±.51 ±.97) 1 7 B(D KKµµ) = (1.54 ±.27 ±.9 ±.16) 1 7 q ū u q u ū h h + µ µ + c 2 /MeV] 1 db/dm [1 c 2 /MeV] 1 db/dm [ D π + π µ + µ m(µ + µ ) [MeV/c 2 ] + D K K µ + µ m(µ + µ ) [MeV/c 2 ] 19 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 19/26 26

22 D hhµµ The challenge is to disentangle the SD and LD. Angular observables can help: ~nµµ µ + h ~n hh µ ~e µ+ ~ehh ~e h ~e µ ~e µµ D ~e h + h [arxiv: ] A F B = Γ(cos θ µ > ) Γ(cos θ µ < ) Γ(cos θ µ > ) + Γ(cos θ µ < ) µ h + A 2ϕ = Γ(sin 2ϕ > ) Γ(sin 2ϕ < ) Γ(sin 2ϕ > ) + Γ(sin 2ϕ < ) Γ(D hhµµ) Γ(D hhµµ) A CP = Γ(D hhµµ) + Γ(D hhµµ) Analysis with 5 fb 1. See M. Gersabeck talk for more details! Candidates per 5 MeV/c (a) Data Fit D π + π µ + µ D π + π π + π Comb. backg m(π + π µ + µ ) [MeV/c 2 ] 2 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 2/26 26

23 D hhµµ [arxiv: ] Need to perform a 4D acceptance correction. BDT technique used to determine it. A FB A 2φ Candidates per simulation D π + π µ + µ Generated Selected A CP D π + π µ + µ m(µ + µ ) [MeV/c 2 ] A FB D π + π µ + µ m(µ + µ ) [MeV/c 2 ] Weighting BDT output.2.4 D π + π µ + µ.2.4 D K + K µ + µ weight (1/ε) Yields done by a weighted likelihood fit. A 2φ m(µ + µ ) [MeV/c 2 ] A CP m(µ + µ ) [MeV/c 2 ] All observables consistent with!.4.6 D K + K µ + µ m(µ + µ ) [MeV/c 2 ].4.6 D K + K µ + µ m(µ + µ ) [MeV/c 2 ] 21 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 21/26 26

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25 K S µµ pp collisions create enormous amount of strange mesons. Can be used to search for K S µµ. SM prediction: Br(K S µµ) = (5. ± 1.5) 1 12 Dominated by the long distance effects. Bkg dominated by K S ππ. EUR. PHYS. J. C, 77 1 (217) 678 No significant enhancement of signal has been observed and UL was set: Br(K S µµ) <.8(1.) 1 9 at 9(95)% CL 23 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 23/26 26

26 ) Σ pµµ Σ pµµ is a s d transition, which in SM are dominated by LD: O(1 8 ). PHYS. REV. LETT. 12, (218) µ + µ + Σ + s u γ, Z W u, c, t µ d u p Σ + s u W γ µ u d p u u u u Previously HyperCP ( collaboration ) reported evidence of this decay: B(Σ pµµ) = ± [Phys Rev Lett , 25] Calibrated with K πππ: resolution of 4.28 MeV/c 2. Used 3 fb 1 of data. Candidates / ( 1.2 MeV/c K + π + π π Data Full model K + π + π π + Background m π + π π [MeV/c 2 ] + 24 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 24/26 26

27 ) R ) ) Σ pµµ EUR. PHYS. J. C, 77 1 (217) 678 Normalize to Σ pγ. Candidates / ( 2.4 MeV/c Σ + pπ Data Full model Σ + pπ Background corr m Σ [MeV/c 2 ] Evidence with 4.1 σ significance. Branching fraction measured: ( B(Σ pµµ) = ) 1 8 Candidates / ( 5 MeV/c 2 Weighted candidates / ( 2 MeV/c Σ pµ + µ Data Full model + Σ pµ + µ Background m [MeV/c 2 pµ + µ ] 4 Data + Σ pµ + µ PS Model m [MeV/c 2 µ + µ ] 25 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 25/26 26

28 Summary FCNC processes provide powerful constraints on extensions of the SM. Large bb cross-section provides a large sample of rare decay processes. More results being updated with Run2 data. Stay tuned for more results! 26 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 26/26 26

29 Backup 27 / M.Chrzaszcz (CERN) Rare decays in the beauty, charm and strange sector 27/26 26