Mixing and Coherence in D Mesons Onur Albayrak (Carnegie Mellon - PowerPoint PPT Presentation

Mixing and Coherence in D Mesons Onur Albayrak (Carnegie Mellon University) on behalf of the BESIII Collaboration albayrak@phys.cmu.edu May 20 - Charm 2015 - Wayne State University 1

BEPC II Storage ring A -charm factory z Υ 10 3 J / ψ ψ (2S) Institute of High Energy Physics (IHEP) campus 10 2 Beijing, China φ ω R 10 ρ ′ Beam energy: 1.0 - 2.3 GeV Energy spread: 5x10 -4 1 BESIII (direct) L peak : 0.7x10 33 /cm 2 s ρ BESIII (ISR) -1 10 1 10 √ s [Ge V] 2 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015 BESIII Spectroscopy | W. Gradl | 10

BESIII Detector BESIII data sets BESIII data sets Beijing Electron Spectrometer 104 energy points between 3.85 and 4.59 ��� 1300 20 energy points between 2.0 and 3.1 GeV 600 ( ongoing ) Direct production of 1 states studied with world's largest scan dataset BESIII Spectroscopy | W. Gradl | 12 3 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015 104 energy points between 3.85 and 4.59 ��� 20 energy points between 2.0 and 3.1 GeV ( ongoing ) Direct production of 1 states studied with world's largest scan dataset BESIII Spectroscopy | W. Gradl | 12

̅ Outline D Tagging • • Measurement of y CP in D 0 -D 0 oscillation GGSZ Analysis of D 0 → K 0 π + π - • 4 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ ̅ D Tagging + K - DD pairs are produced while running at 3.773 GeV ~93% the time K D 1 - + e e (3770) ψ D Tagging is used for selecting events. D 2 K Single Tag, Fully reconstruct one D decay e( ) µ ν e( µ ) Double Tag, when the partner D is also reconstructed. Single Tag (ST): Tag modes are reconstructed requiring a � � beam / c 4 − | ⃗ ≡ E 2 p D | 2 / c 2 certain window for the Δ E variable. M BC ≡ � E ≡ E D − E beam Example fits M BC distribution is fit to calculate tag yields. Double Tag (DT): Depending on the D decay that is being studied, M BC or some other variable will be used to calculate double tag yields. Both analyses that I will be talking about use D Tagging. 5 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ Outline D Tagging • Measurement of y CP in D 0 -D 0 oscillation • GGSZ Analysis of D 0 → K 0 π + π - • 6 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ ̅ ̅ ̅ Measurement of y CP in D 0 -D 0 oscillation At BESIII we are capable of producing D 0 D 0 pairs Oscillations in D 0 -D 0 system at threshold with a definite C = − 1 state. are characterized by ers x = � m / Ŵ D mesons will have opposite CP . and y = �Ŵ / 2 Ŵ , Semileptonic decays of D 0 are used for probing the mixing parameter. mass and the width differences between two mass eigenstates alue: Ŵ CP ± = Ŵ ( 1 ± y CP ) . as | D 1 , 2 ⟩ = p | D 0 ⟩ ± q | D 0 ⟩ , ⟩ = | ⟩ ± Branching fraction of a semileptonic decay becomes: ers and = arg q p is a φ = arg ( q / p ) is B D CP ± → l ≈ B D → l ( 1 ∓ y CP ) , ention CP | D 0 ⟩ = + rewrite � B D CP − → l − B D CP + → l � y CP ≈ 1 | D CP − ⟩ ≡ | D 0 ⟩ − | D 0 ⟩ 4 B D CP + → l B D CP − → l √ 2 use D 0 D 0 allowing small indirect CPV �� � � � �� � � � y CP = 1 � q p � q p �� � � � � � � � � y cos φ � + − x sin φ � − . � � � � � � � � 2 p q p q � � � � � � CP eigenstate Semileptonic in the absence of CPV y CP reduces to or opposite y with |q/p| = 1 and 𝜚 = 0 · ε CP ± B D CP ∓ → l = N CP ±; l , ε CP ±; l N CP ± 7 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ Measurement of y CP in D 0 -D 0 oscillation + K Decays used in the analysis - K K + K − , π + π − , K 0 S π 0 π 0 CP + D 1 K 0 S π 0 , K 0 S ω , K 0 - CP − S η + e e (3770) ψ K ∓ e ± ν , K ∓ µ ± ν Semileptonic Double Tag (DT): D 2 K After reconstructing the CP tag, semileptonic e( ) µ ν e( µ ) decay of the pair D meson is reconstructed The U miss distribution is fit to calculate the DT Single Tag (ST): yields. CP tag modes are reconstructed as single tags. U miss ≡ E miss − c | ⃗ p miss | , Example fits E miss ≡ E beam − E K − E l , ≡ − − � � � � beam / c 2 − c 2 m 2 E 2 p miss ≡ − ⃗ p K + ⃗ ⃗ p l + ˆ p ST D background main K ππ 0 Quite clean after the analysis requirements, U miss provides better resolution compared to M 2miss 8 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ Measurement of y CP in D 0 -D 0 oscillation - Results Yields are then used to calculate the HFAG- charm CHARM 2012 branching ratio, with the efficiency measured using the MC sample 0.732 ± 2.890 ± 1.030 % E791 1999 · ε CP ± B D CP ∓ → l = N CP ±; l 3.420 ± 1.390 ± 0.740 % FOCUS 2000 , ε CP ±; l N CP ± -1.200 ± 2.500 ± 1.400 % CLEO 2002 Branching ratios of Ke 𝜉 and K 𝜈𝜉 are 0.110 ± 0.610 ± 0.520 % Belle 2009 summed to calculate 𝓒 CP± → ℓ Results are then combined for different 0.550 ± 0.630 ± 0.410 % LHCb 2012 CP modes using the standard weighted 1.110 ± 0.220 ± 0.110 % least-square method, minimizing, Belle 2012 0.720 ± 0.180 ± 0.124 % BaBar 2012 � 2 � ˜ B D CP ± → l − B α D CP ± → l χ 2 = � � 2 � σ α α CP ± 0.866 ± 0.155 % World average -4 -3 -2 -1 0 1 2 3 4 5 Result: y CP = ( − 2.0 ±1.3 (stat) ±0.7 (sys) )% y CP (%) HFAG - arxiv:1412.7515 Phys.Lett. B 744 (2015) 339-346 9 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ Outline D Tagging • • Measurement of y CP in D 0 -D 0 oscillation GGSZ Analysis of D 0 → K 0 π + π - • 10 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ ̅ ̅ Strong Phase Difference b/w D 0 and D 0 → K 0 𝜌 + 𝜌 − Motivated by the quest to increase the precision * / V cd V cb * � � � arg � � V ud V ub of the angle 𝛿 measurement in B − → DK − decay. 1.5 excluded at CL > 0.95 excluded area has CL > 0.95 Determine 𝛿 through the interference between b → c and γ 1.0 m & m ∆ ∆ b → u transitions when 𝐸 0 and 𝐸 0 both decay to the same s d sin 2 β final state f(D). 0.5 m ∆ d ε α K β γ η A ð B � ! K � ~ D 0 ! K 0 0.0 D 0 K − D 0 ; ~ S � þ � � ð x; y ÞÞ α V α ub / f D ð x; y Þ þ r B e i � � f � D ð x; y Þ : -0.5 B − f(D)K − and � � � � B � � , ε -1.0 K between the color- CKM Here, x � m 2 S � þ , y � m 2 D 0 K − γ sol. w/ cos 2 β < 0 f i t t e r S � � K 0 K 0 (excl. at CL > 0.95) FPCP 13 ~ 0 ð Þð ference � � D � � D ð x; y Þ � � D ð y; x Þ , -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 ρ ð Þ BESIII can help reducing the systematics on We will use the GGSZ* method to investigate the decay this important measurement with Final states are three body, self-conjugate modes providing more information on the eg: K s KK, K s 𝜌𝜌 - Binning regions of Dalitz plot where δ D is similar D 0 → K 0 𝜌 + 𝜌 − decay. - Model independent, there is no incorrect binning. With the amount of data LHCb collecting, - Optimization for binning for increased sensitivity. 𝛿 measurement soon will be systematically *Giri, Grossman, Soffer, Zupan ( GGSZ ) limited. Phys. Rev. D 68 (2003) 054018 11 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ Strong Phase Difference b/w D 0 and D 0 → K 0 𝜌 + 𝜌 − ° α /ϕ 2 = 85.4+4.0 Dalitz Plot −3.9 ° β /ϕ 1 = 21. 38+0.79 s13 3 −0.77 • T i : measured in flavor decays 2.5 ¯ th bin The i ° 𝛿/ϕ 3 = 68+8.0 • r B : color suppression ~0.1 of symmetry 2 −8.5 • δ B : strong phase of B 1.5 • c i ,s i : weighted average of cos( Δδ D ) and sin( Δδ D ), 𝛿 • 1 phase difference between Ds given by Δδ D . 𝛿 0.5 • All but c i ,s i variables will be measured in B factories. 3 s12 0.5 1 1.5 2 2.5 78.4+10.8 the i th −11.6 𝑡𝑢𝑏𝑢 ± 3.6(𝑡𝑧𝑡𝑢) ± 8.9(𝑁𝑝𝑒𝑓𝑚) • 𝛿 c i = c i and s i = -s i the i th Belle model Belle Model-Independent Dalitz 77.3+15.1 independent 𝛿 −14.9 𝑡𝑢𝑏𝑢 ± 4.2(𝑡𝑧𝑡𝑢) ± 4.3(𝑑 𝑗 /𝑡 𝑗 ) • c i ,s i error dominates measurement Currently statistically limited, Phys. Rev. D 85, 112014 (2012) � d Γ ( B ± → ( K 0 S π − π + ) D K ± ) Γ ± ( i ≡ i � = T i + r 2 B T ı ± 2 r B T i T ı [cos( δ B + γ ) c i − sin( δ B + γ ) s i ] ( 12 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015

̅ Strong Phase Difference b/w D 0 and D 0 → K 0 𝜌 + 𝜌 − c i ,s i can be measured using the Double Tags: D 0 → K s 𝜌 + 𝜌 − vs (K S/L 𝜌 + 𝜌 − or CP tags) c i and s i c ’i and s ’i [K s 𝜌 + 𝜌 − vs CP tags] [K L 𝜌 + 𝜌 − vs CP tags] [K S 𝜌 + 𝜌 − vs K S 𝜌 + 𝜌 − ] [K L 𝜌 + 𝜌 − vs K S 𝜌 + 𝜌 − ] Use both (c i , s i ) and (c ’i , s ’i ) to further constrain the results (c i , s i ) Babar optimized Binning Scheme 2008: Optimized to increase sensitivity to 𝛿 , and smooths the bins to account for the regions that are smaller than the detector resolution. 13 Onur Albayrak - CMU - BESIII Collaboration - Charm 2015