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Discovering CP Violation and Mixing in the Charm Sector. NEW. D + production asymmetry ΔA CP y CP , A Γ CPV search in four-body pion. On behalf of the LHCb(c?) collaboration. Muon System. Vertex Locator. RICH Detectors. Interaction Point. Tracking System. Calorimeters.

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discovering cp violation and mixing in the charm sector

Discovering CP Violation and Mixing in the Charm Sector

NEW

D+ production asymmetry

ΔACP

yCP, AΓ

CPV search in four-body pion

On behalf of the LHCb(c?) collaboration

slide2

Muon System

Vertex Locator

RICH Detectors

Interaction

Point

Tracking System

Calorimeters

Chris Parkes

lhc b lhc c
LHCbLHCc

c

  • LHCb was designed for b-quark studies
  • But also ideal for charm
    • shorter lived and lower p
    • 20 times more events

Chris Parkes

charm prompt and secondary
Charm – Prompt and Secondary
  • Two types of charm production:
    • Prompt:

charm produced directly

in the primary reaction

    • Secondary:

charm produced in

B decays [>50% of B->DX]

      • Prompt charm more abundant
      • Secondary can have higher purity
  • Must discriminate between them
    • Use D impact parameter

Chris Parkes

d production asymmetry
D± production asymmetry
  • Time-integrated direct CPV searches are sensitive to production effects
  • Initial pp – no net charm !
  • Direct production QCD/EW – cc
  • But hadronisation with valence quarks can break

D+/D- symmetry

  • Previously measured
  • Measure:
  • using

NEW

LHCb-PAPER-2012-026 to be submitted to PLB

Chris Parkes

cpv in decay
CPV in decay ?
  • CPV in D+ ? Cabbibo allowed, tree
    • Expected 10-4. Measured by Belle
  • CPV in Ks considered

Grossman, Nir arXiv:1110.3790

  • Ks decaying inside VELO used
    • Short lifetime
      • (mean 7ps, c.f. 90 ps)
    • Fold with indirect CPV in Ks, ε
    • Effect is small
      • 2.8 x 10-4

Preliminary

LHCb-PAPER-2012-026 to be submitted to PLB

Chris Parkes

result prelim
Result (prelim.)
  • Measurement performed in bins (pT,η)

Preliminary

Preliminary

  • In kinematic region probed:
    • 3 σ evidence for a production asymmetry
    • No significant dependence on pT,η seen at this statistics

Primary systematic

from trigger asymmetry

LHCb-PAPER-2012-026 to be submitted to PLB

Chris Parkes

direct cp violation in two body charm
Direct CP violation in two-body charm
  • Search for CP asymmetry
  • Use decays

where slow pion charge determines the D flavour at production

(used in all analyses that follow in this presentation)

What we

measure

What we

want

What we

don’t want (1)

What we

don’t want (2)

Phys. Rev. Lett. 108, 111602 (2012)

production asymmetry of d
Production Asymmetry of D*+
  • Technical Scale Drawing of LHC Collision

Proton (Matter)

Proton (Matter)

+ve charge

  • Cancel by measuring difference of KK and ππ final states

-ve charge

Detection Asymmetry of D and of π+s

  • Symmetric final states
  • no D detection asymmetry
  • Difference of final states
    • cancel π+s detection asym.
  • Periodic reversal of magnetic field

Phys. Rev. Lett. 108, 111602 (2012)

Chris Parkes

subtle reconstruction effects
Subtle Reconstruction Effects

Regions of phase space where only a D*+ or D*- can be reconstructed, due to LHCb detector geometry

While in principle they cancel in magnet reversal they are removed using

fiducial cuts

π+s reconstructed

π-s not reconstructed

Phys. Rev. Lett. 108, 111602 (2012)

Chris Parkes

slide11

Direct CP Violation in Charm

  • High Statistics
    • 1.4M K+K-, 0.4M π+π-
  • 0.6 fb-1 analysed,
  • now have 2.5 fb-1 recorded
  • Many cross-checks have been performed
  • Independent analysis using secondary charm in preparation

Phys. Rev. Lett. 108, 111602 (2012)

Chris Parkes

results
Results
  • First evidence of CPV in charm decays
  • Supported by recent CDF and Belle results

ΔACP = [-0.62 ± 0.21 (stat) ± 0.10 (syst)]%

ΔACP = [-0.87 ± 0.41 (stat) ± 0.06 (syst)]%

Phys. Rev. Lett. 108, 111602 (2012)

Chris Parkes

slide13

Until recently most calculations suggested CPV in charm < 10-3

    • There are honourable exceptions e.g. “…There is no theorem, though, ruling out SM effects of 1%”

S. Bianco, F. L. Fabbri, D. Benson, and I. Bigi, A Cicerone for the physics of charm, Riv. Nuovo Cim. 26N7 (2003)

  • 89 citations for LHCb paper
  • Consensus?
    • Compatible with NP models,
    • Large for SM but NOT excluded

Theorists

Phys. Rev. Lett. 108, 111602 (2012)

Chris Parkes

time dependent two body measurements
Time-dependent two-body measurements
  • Lifetime ratio measurements:

Pure mixing measurement

In absence of CPV

  • Measured for first time at a hadron collider
  • 2010 (0.03 fb-1) data only

CPV indirect (and direct)

JHEP04 (2012) 129

Chris Parkes

measuring propertime acceptance
Measuring propertime acceptance
  • Determined from data
  • “swimming” – move the D vertex and reapply the selection
  • LHCb trigger – all lifetime biasing selections in software

JHEP04 (2012) 129

Chris Parkes

measuring propertime acceptance1
Measuring propertime acceptance

JHEP04 (2012) 129

Chris Parkes

measuring propertime acceptance2
Measuring propertime acceptance

JHEP04 (2012) 129

Chris Parkes

measuring propertime acceptance3
Measuring propertime acceptance

JHEP04 (2012) 129

Chris Parkes

measuring propertime acceptance4
Measuring propertime acceptance

JHEP04 (2012) 129

Chris Parkes

prompt secondary separation
Prompt/Secondary Separation
  • Separate prompt /secondary charm on statistical basis through ln(χ2 IP of D)
  • Primary systematic, improve with better secondary modelling

JHEP04 (2012) 129

Chris Parkes

results1
Results
  • Based on 2010 data, 0.03 fb-1

JHEP04 (2012) 129

Chris Parkes

four body cpv search
Four-body CPV search
  • Model independent search
  • Four-body “Dalitz” plot, 5 dimensions
  • Compare bins across phase space
  • Sensitive to local variations
    • SCP normal (μ=0,σ=1) in absence of CPV
  • α – normalisation – insensitive to global asymmetries
    • global CP and global detector/production effects
  • Adaptive binning >100 entries/bin

LHCb-CONF-2012-019

Chris Parkes

detector production asymmetries
Detector/production asymmetries
  • Equal amounts of two magnet polarities
  • Apply fiducial cuts (as earlier)
  • Accept/reject in (η,ϕ) space for equal D,D

2011 1fb-1 data, 180k events, 96% purity

LHCb-CONF-2012-019

Chris Parkes

cpv search results
CPV Search Results
  • Method cross-checked
    • CF decay
    • Simulated phase differences
  • No evidence of CPV in
    • P-value 99.8%

LHCb-CONF-2012-019

Chris Parkes

summary
Summary
  • LHCb’s huge charm samples fulfilling potential
  • D± production asymmetry
    • 3σ evidence
  • ΔACP with CDF+Belle, 4.6σ evidence of CPV
    • No lose theorem:
      • New Physics OR the FBI arrest a theorist
  • yCP and AΓ
    • First hadron collider measurement – precision results to come
      • Acceptance effect from data
  • 3 and 4-body CPV searches
    • Binned (generalised) Dalitz plot searches

NEW

(KKπ Phys. Rev. D 84 (2011) 112008)

Chris Parkes

slide26

6th International Workshop on Charm Physics

Manchester, UK, 31 August – 4 September 2013

Topics:

New Charmonium-like Hadrons (XYZ Hadrons)

Hidden Charm Spectroscopy and Transitions

Production of Charm and Charmonia

Hidden and Open Charm in Media

Charm Meson and Baryon Spectroscopy

Light Hadronic Spectroscopy from Decays of Charm and Charmonia

Leptonic, Semileptonic and Rare Charm Decays

Advances in Theoretical Tools

D -Dbar Mixing and CP Violation

New Physics Scenarios for Charm Decays

Experimental Charm Facilities - Status and Future