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Physics with antiprotons: CP violation in D-mesons Klaus Peters Ruhr-Universität Bochum KVI Groningen Jan 7, 2003.

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Presentation on theme: "Physics with antiprotons: CP violation in D-mesons Klaus Peters Ruhr-Universität Bochum KVI Groningen Jan 7, 2003."— Presentation transcript:

1 Physics with antiprotons: CP violation in D-mesons Klaus Peters Ruhr-Universität Bochum KVI Groningen Jan 7, 2003

2 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Overview CP-Violation Introduction The K, B and D-case D-Mesons Production Decays Experimental Techniques Applications at PAnDa Experiments and Techniques Requirements and Limitations

3 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Motivation CP-Violation was first observed 1963 Christenson, Cronin, Fitch & Turlay The origin is not well established yet SM, QCD, non-SM, … CP-Violation – important for Baryogenesis Baryon asymmetry Is well measured in the K-System and observed in the B-System  ’/ , sin2 , sin2  No evidence in D-Systems yet SM prediction: small, discovery  new physics

4 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Quark-Mixing Not all neutral mesons are C-Eigenstates (like the  0 ) but K 1 and K 2 are CP-Eigenstates

5 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Types of CP Violation = / 2 I F _ I _ F 2 = / 2 I _ I _ F 2 I F _ I = / I F 2 I _ I _ F + _ I _ F 2 I F _ I + direct CP Violation

6 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The Kaon Case Observation: K 0 S c  =2.68 cmdecay dominant 2 , CP=+1 K 0 L c  =15.51 mdecay dominant 3 , CP=-1 m=(3.49±0.04)x MeV/c 2 but sometimes |  =(2.282±0.017)x10 -3 ~ (K L 2)/(K S 2) a K 0 L decays to 2  dominated by mixing in addition there is also direct CP violation without mixing Re(  ’/  )=(1.8±0.4)x10 -3

7 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Analysis Overview K S K L Concept 1 –Tagged Mode Identify K S neither definite CP nor Flavor Measure decay time differences Tagging – Systematics! Concept 2 - Untagged Mode Measure decay time difference untagged No systematics due to tagging smaller statistics since both final states must be similar (like (K S K L )        )

8 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The Da  ne Detector e + e -   (1020) K S : Large decay volume: low density TPC Main CP channel K S K L         –detection for neutral  0 reconstruction

9 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The CKM Matrix Unitarity relation e.g. V ub V ud *+V cb V cd *+V tb V td *=0 can be expressed as a triangle in complex space CP-Violation parameters ,  and  measured quantity sin2  C=(0,0)B=(1,0) A=( ,  )   Wolfenstein Parameterization O( 4 ) ’/’/

10 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The B-Meson Case: closing the triangle The lifetime difference in the B-System is much smaller than in the K-System instead of nearly perfect CP-Eigenstates K S /K L strong Eigenstates CP violation appears in the time dependent decay rate

11 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Analysis Overview Y(4s)BBbar Basic concept Measure the B 0 time dependent decay rate of channels with definite CP Need to know the flavor of the B 0 – Flavor Tagging! Although 2 B’s are present – only need to reconstruct B 0 CP fully if one can “measure” the flavor of the B tag. Gauge the Flavor-Tagging with fully reconstructed events To be included Dilution due to Miss-Tag Resolution smearing

12 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Analysis Overview Y(4s)BBbar reconstruct exclusive B decays to CP and flavour Eigenstates and tag the flavour of “the other B” select B tag events with leptons and kaons from hadronic B decays and determine B flavour measure Miss-Tag w i and determine dilution D i =1-2w i effective Q i =(1-2w i ) 2 select B CP candidate (like B 0  J/  K 0 S, etc.) and B flavor candidates (like B 0  D* -  + ) measure  z between B CP and B tag and determine the signed time difference  t between decays

13 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa ) DIRC (PID) 1.5T solenoid Drift Chamber Silicon Vertex Tracker e + (3.1GeV) e - (9GeV) Tracking : (p T )/p T = 0.13% P T % DIRC : K- p separation >3.4 s for p<3.5 GeV/c EMC:  E /E = 2.3% E -1/4  1.9% CsI(Tl) EMC Instrumented Flux Return The BaBar Detector

14 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa single vertex resolution s ~70 m m stand-alone tracking for low p t particles (<120 MeV/c) 5 layers double sided channels surface ~1m 2 point resolution s =15(40) m m for inner (outer) layers B A B AR : Silicon Vertex Tracker

15 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Charm (c) + Light Quark (u,d,s) H-Atom of QCD decay: destroying charm quantum number no strong decays only weak (or non-SM) decays long lifetimes c  ~  m many channels into light mesons individual channels are usually rare D-Mesons – Basic Properties

16 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa W c u,d,s W c d,s W c u,d,s W c W-emission (external)W-emission (internal) W-annihilationW-exchange D (S) -Decays

17 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Cabbibo-Suppression CKM-Matrix: allowed transitions V ii ~1 (cos c ) suppressed transitions V ij <1 (sin c ) Colour-Suppression: W-Boson creates a Quark- Antiquark-Pair with matching colour-anticolour (~1/3 2 =1/9) = u c ds ~cos c ~sin c ~-sin c W q q _ D (S) -Decays

18 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa W c u _ u _ d _ u s ++ D0D0 KK W c s _ s _ d _ u s ++ DS+DS+  W c d _ d _ d _ u s ++ D+D+ KK _ D (S) -Decays W c u _ u _ d _ s u D0D0  KK _ W c d _ d _ d _ s u D+D+ KK _ ++ W c s _ s _ d _ s u DS+DS+ K+K+ KK _

19 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The D-Meson Case: discovery opportunities for direct effects The DDbar mixing diagrams are suppressed small mass of d-,s- and b-quarks ~f(m s )-f(m d ) BB bar and KK bar enhanced due to t-quark mass ~m t 2 Using x D =m/ and y D =/2 Osc. parameter r D =1/2 (x D 2 +y D 2 ) r D =(D 0 l-X)/(D 0 l+X)  only bounds SM prediction r D =10 -8 with possible strong phase  between RS and WS x‘=x cos+y sin y‘=y cos-x sin

20 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D-Mesons: Mixing and Indirect CP Violation „Wrong sign“ (WS) D 0 decays either produced via DCS or mixing and CFD mixing parameter y can be extracted from lifetime ratio y=  K /  KK -1 K  has no certain CP parity K + K - is a CP even mode Indirect CP violation occurs in the mixing if expected asymmetry is very small (~10 -5 ) only new physics can lead to asymmetries as large as 1%

21 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D-Mesons: Experimental results and predictions new physics y SM x SM

22 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D-Mesons: Direct CP violation Recently observed in K meson decays (NA48/kTeV) requires two coherent amplitudes with different weak phases and strong phases only SCS decays can be used where tree and one-loop penguin interfere expected asymmetry A CP ~ -2 ~ possible decay modes D 0 K + K -,   ,K S  0,  0  0,K S K S or D + K S  +

23 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa p  D D  g Photo-Production D D  g,P  p h Central Production E769 E687,E791,E831 (Focus) D (S) -Production

24 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa E687 Photo-Production

25 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D B l, l D B h W D B h W D D e+e+ ee n  /K Babar,Belle,Cleo-C D (S) -Production

26 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D D p p _ D D p p _ D D e+e+ ee Threshold production Mark-III,Cleo-C Panda D (S) -Production

27 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa CLEO-C (CESR-C) in 2003 CESR-c and CLEO-c become operational sqrt(s)=3 -5 GeV/c 2 L=( ) x cm -2 s -1 3 yr. running envisaged E cm LInt LEvents GeV10 32 cm -2 s -1 fb (4m) 1.3x10 9 J/ 3.69~ (4m) 10 9 ‘ 3.77~4.133 (9m)3x10 7 DD 4.14~4.43 (9m)1.5x10 5 D s D s 4.6~4.41 (3m) 4x10 5  C  C

28 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa High Rates Total  ~ 55 mb Vertexing ( p,K S,,…) Charged particle ID (e ±, ±, ±,p,…) Magnetic tracking Elm. Calorimetry (, 0,) Forward capabilities (leading particles) Sophisticated Trigger(s) Proposed Panda Detector (Overview)

29 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa 7.2 mio. barrel pixels 50 x 300 μm 2 mio. forward pixels 100 x 150 μm beam pipe pellet/cluster pipe Readout: ASICs (ATLAS/CMS) 0.37% X 0 or pixel one side – readout other side (TESLA) Panda-Vertexing: Micro Vertex Detector

30 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa less space than aero gel  costs of calorimeter no problems with field Panda-PID: DIRC (Cherenkov)

31 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Charm and Double-Charm Production Charm production is not investigated in low energy pp bar reactions so far First goal: measure charm (D-meson, C-Hyperon) production reconstruct exclusive channels measure inclusive cross sections measure decay topologies be prepared for surprises! like double ccbar production in e + e - in e + e - J/X at Y(4s), 60% of X contains cc bar ! Use this input for the design of a CP-violation experiment at PAnDa in a later stage

32 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D-Pair Production and D*-Tagging D-mesons can be produced directly in pp bar reactions Use D* mesons as a source for D 0 B(D* + D 0  + )=68% D* + D 0  + is a CP-conserving strong decay the charge of the slow! pion is an unbiased flavor tag for the D 0 (DD bar ) ~ nb rec. events ~10 6 /year Alternative technique ppp  C + D 0 with perfect flavor tag but yield unknown and no dominant  C decay channel _

33 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa D-Trigger Properties for a possible trigger lifetimes  m slow (recoil) pions from D* moderate multiplicities associated production Lifetimes and momenta require a high trigger level (reco!) multiplicities and K S multiplicity jumps are available “in hardware” Associated production Need to trigger on one D D + K S X= (30±4)% D + K ± X= (30±3)% D 0 K S X= (21±3)% D 0 K ± X= (56±4)% An efficient trigger on charged K’s and K 0 S will maintain more than 50% of the DD bar events Hadronic background: reduced by f~10 -2 ppbarK S X ~<10 -2  tot ppbarK ± X ~<10 -2  tot

34 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Other CP-Measurements in ppbar Non-leptonic decays (|S|=1) proceed by parity-violating weak interaction angular momentum L=0,1  P=(-1) L interference between S- and P-wave or |I|=1/2 and 3/2 observed quantities are angular distribution asymmetry  and baryon decay polarization  (from  decays)

35 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The Hyperon Case: CP conservation implies measure SM prediction A~ ~ 65 b (), 2 b (    ) N  ~ 10 9 /month N  ~ 3x10 7 /month

36 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa The GSI Future Project Panda Existing GSI Facilities

37 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa Summary and Outlook The origin of CP violation is still unclear Using any available tool is mandatory to understand a basic feature of our subnuclear structure The D-system is a great opportunity to study direct CP-violation The new facility at GSI provides a possibility to test CP violation in D-mesons and Hyperon decays

38 Klaus Peters, RUBochum, CP- Physics with D-Mesons at PAnDa GSI & PAnDa: More Information


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