Analysis of a D* + Decay Path and Natural Line Width

Analysis of a D*+ Decay Path and Natural Line Width

Jeff Rodriguez

Mike Sokoloff Rolf Andreassen Carol Fabby

Jeff Rodriguez 204/20/23

Importance of particle physics and general physics research

Spin off technologies- Internet, Computers, Kings Island Answer some simple questions How did the universe come to be? Where is all the anti-matter? Why do objects have mass? What is dark matter and dark energy? Particles, Strings, and Dimensions? The scientist does not study nature because it is useful; he studies it

because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing, and if nature were not worth knowing, life would not be worth living.- Henri Poincaré.


;

advanced software for information-sharing (the World Wide Web), distributed grid-computing and radiation-exposure simulations for space and medical technologies.

accelerators for medical diagnosis, therapies, food-treatment, micro electronics production and energy-generation; radiofrequency power generation

high-field magnets for medical imaging; radiation and imaging detectors for use in pharmaceutical, biological and

materials sciences, medical and security equipment; Novel ‘bionic’ implants A new type of active pixel sensor developed for

the LHC has many applications but the most exciting are retinal implants which have the potential to restore partial sight to the blind.

Hilger Crystals in London had to mass-produce fast-response scintillator crystals for the BaBar experiment, which then allowed the company to supply its products at a price that was attractive to manufacturers of medical imaging equipment.

Importance of particle physics and general physics research


BABAR Experiment The goal of the experiment is to study the

violation of charge and parity (CP) symmetry in the decays of B mesons. This violation manifests itself as different behaviour between particles and anti-particles and is the first step to explain the absence of anti-particles in everyday life.

B-factories confirm matter-antimatter asymmetry; leads to 2008 Nobel Prize in Physics

http://www-public.slac.stanford.edu/babar/Nobel2008.htm


What is so important about this study?

CP violation? If CP symmetry holds, the decay rate of B mesons and their antiparticles

should be equal. Analysis of secondary particles produced in the BaBar detector showed this was not the case – in the summer of 2002, definitive results were published based on the analysis of 87 million B/B meson-pair events, clearly showing the decay rates were not equal. Consistent results were found by the Belle experiment at the KEK laboratory in Japan.

What about this study?


Particle Data Group

D* (2010)+ , D0, and ∆m valuesD* (2010)+ 2008 +/- 3 MeV

D* (2010)+ Width 96 +/-4(stat) +/-22 (syst) keV

D0 1864.84 +/- .17 MeV∆m= m D*+(2010) = m D0 145.421 +/- .01 MeV

D* (2010)+ Decay ModesMode Fraction(Γi /Γ)D0 π + (67.7 +/- 0.5)%D+ π0 (30.7 +/- 0.5)%D+ γ (1.6 +/- 0.4)%


Particle Data Group

D0 Decay ModesInclusive Modes Fraction(Γi /Γ) Scale factor

K- anything (54.7 +/- 2.8)% S=1.3

K0 anything +K0 anything (47 +/- 4)%

K+ anything (3.4 +/- 0.4)%

More…..

Why is fraction>100%?

The D0 and D0 bar are the mass eigenstates of the D0 meson( due to mixing). Need to determine proper description of decay mode


CLEO Detector @Cornell (CESR)

Although CLEO ran mainly near the Υ(4S) to study B mesons, it was also competitive with experiments designed to study charm hadrons. CLEO was the first experiment to measure the doubly Cabibbo suppressed decay D0→ K+π-,[99] and CLEO performed Dalitz analyses of D0,+ in several decay modes.[100] [101] [102] [103] [104] [105]

CLEO studied the D*(2010)+, making the first measurement of its width and the most precise measurement of the D*-D0 mass difference.[106] CLEO-c made many of the most accurate measurements of D meson branching ratios in inclusive channels,[107][108] μ+νμ, [109] semileptonic decays,[110][111] and hadronic decays. [112][113][114]

These branching fractions are important inputs to B meson measurements at BaBar and Belle. CLEO first observed the purely leptonic decay Ds+→μ+ν,[115] which provided an experimental measure of the decay constant fDs.

CLEO-c made the most precise measurements of fD+[116] and fDs.[117] These decay constants are in turn a key input to the interpretation of other measurements, such as B mixing.[118]


K-

e -

Signal Side

Tag Side

D*+

π+

D0

e +

π+

These particles

reach layers of the

detector

Decay being studied (for D*+ natural line width): D*+ D0 π+

D0 K- π+ π0

π0

Note-Decay image altered from Carol Fabby’s analysis


D0 mass vs ∆m


D0 mass distribution.1461>∆m>.1447

What happened to stat boxes?


D0 mass Region Selections

Central Signal Region 1.835-1.855 GeV/c2

Upper Signal Band 1.865-1.885 GeV/c2

Lower Signal Band 1.835-1.855 GeV/c2

Upper Side Band 1.940-1.960 GeV/c2

Lower Side Band 1.760-1.780 GeV/c2


D0 Mass Cuts on ∆m


Tag SVT and Drift Chamber selection

Make requirements on number of hits to have well measured tracks:

Pion SVT OKKaon SVT OKSlow Pion SVT OK

For high quality tracks, good track resolution and to remove background:

Kaon DCH Hits > 20Pion DCH Hits > 20


TagSVT and nDch Cuts


Cabibbo Favored vs. Doubly Cabibbo Suppressed“Right Sign vs. Wrong Sign”

99.7% favored 0.3% favored


Cabibbo Favored vs. Doubly Cabibbo Suppressed“Right Sign vs. Wrong Sign”


π CF(+/+) vs CDS(+/-)


Something here about how the calorimeter picks up 2 photons as a means of determining the detection of pi 0 and thus the probability that a particle detected is a pi 0

Also something about chi2 analysis


Plots of π0 Chi2 probability function


Probability of π0 Chi2 >0.2


Dalitz plot explanation

K- (m1

)

D0(M)

π+(m2

)

π 0 (m3

)


Dalitz plot explanation (cont.)

http://en.wikipedia.org/wiki/Dalitz_plot

http://pdg.lbl.gov/2009/reviews/rpp2009-rev-kinematics.pdf

Dalitz description pge4

Don’t forget invariant mass description


Dalitz Plots of Signal regionNeed extra code to clean up outsides of plot


Dalitz CutsNew code will be needed to determine regions of high cross product m2 rather than using ranges


Kinematic Limits 3-body decay

http://en.wikipedia.org/wiki/Particle_decay http://pdg.lbl.gov/2009/reviews/rpp2009-

rev-kinematics.pdf Put in equations here and description of 3

particle decay Try and calculate angle in lab vs cm and

compare?


P and Energy (lab and CM)


Center of Mass Momentum Cut


Effect of all cuts on ∆m


MC Truth Matching

• Not just verifying the decay mode exists

• Goal: find best match for D0 and check the mode

• “Top down” approach – Find the best match for the D*+, πs,

D0 (verify D*+ D0πs) – Find best match for the D0

daughters – From prev. step you know you have

the D0 – Make the separate categories for

signal mode and bkg

Real D0, Real πs

Real D0, Not πs

Not D0, Real πs

Not D0, Not πs

Zach Huard Presentation on Truth


Example Event - Event 0 /data/huard/05Jul10_MC_MWDstStudy/SP*.root"


Event info

Analysis of a D* + Decay Path and Natural Line Width

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