Andrew SmithMay 2006, Milagro Collaboration

Meeting

Energy Determination using X2 and NFit

Andrew SmithUniversity of Maryland

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Energy Determination Method - Crab

• Measure event excess in 7 independent “slices” in x2 and NFit.

• Simulate each reconstruction epoch• Use the MCAnalysis “sensi()” method to compute

the number of events/day vs alpha.• Find minimum ChiSq for (A,alpha).• All analysis done using Geant 2.0 and “dev”

version of electronic and noise simulation.• VV’s PMT simulation is included by default.• PE levels were “rescaled” to be appropriate for old

calibrations.

Andrew SmithMay 2006, Milagro Collaboration

Meeting

CutsCuts

(NF>=20 && X2>2.5) && !(NF>=50 && X2>3.0)

(NF>=50 && X2>3.0) && !(NF>=75 && X2>3.5)

(NF>=75 && X2>3.5) && !(NF>=100 && X2>4.0)

(NF>=100 && X2>4.0) && !(NF>=125 && X2>4.5)

(NF>=125 && X2>4.5) && !(NF>=150 && X2>5.0)

(NF>=150 && X2>5.0) && !(NF>=175 && X2>5.5)

(NF>=175 && X2>5.5)

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Energy Determination Method

• Use x2/NFit slices used in weighted analysis.

• Exploit energy dependence of the cuts.

• Theta < 30 deg• Alpha = -2.4

spectrum

Cut Median E (GeV)

1 2884

2 4169

3 5495

4 7244

5 11482

6 13804

7 23988

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Epochs• Single layer Fitters

– Epoch 1 – COM core fitter– Epoch 2 – OFF core fitter– Epoch 3 – ORCOM core fitter

• Multilayer Fitters– Epoch 4 – Gaussian core fitter - 3 layer core fitter– Epoch 5 – Gaussian core fitter

- 2 layer core fitter

• Analysis strategy:– Combine epochs 1-3 and simulate as OFF only– Combine epochs 4-5 using “nfit_2layerEquiv”

and simulate as epoch 5.

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Crab Spectrum Epochs 1-3

Fit Spectrum:

5.70x10-7 E-2.60±0.08

2 =6.5/5 d.o.f.

Crab Cyg Hot Spot Cyg Diffuse

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Andrew SmithMay 2006, Milagro Collaboration

Meeting

Crab Fit Results for Epochs 1-3alpha | A,Chisq | = 2.00 | 1.35 39.89 alpha | A,Chisq | = 2.05 | 1.56 35.30 alpha | A,Chisq | = 2.10 | 1.79 30.92 alpha | A,Chisq | = 2.15 | 2.04 26.80 alpha | A,Chisq | = 2.20 | 2.33 22.96 alpha | A,Chisq | = 2.25 | 2.64 19.45 alpha | A,Chisq | = 2.30 | 2.99 16.29 alpha | A,Chisq | = 2.35 | 3.36 13.53 alpha | A,Chisq | = 2.40 | 3.77 11.19 alpha | A,Chisq | = 2.45 | 4.21 9.30 alpha | A,Chisq | = 2.50 | 4.68 7.88 alpha | A,Chisq | = 2.55 | 5.18 6.96 alpha | A,Chisq | = 2.60 | 5.70 6.54 --- minimumalpha | A,Chisq | = 2.65 | 6.25 6.64 alpha | A,Chisq | = 2.70 | 6.82 7.25 alpha | A,Chisq | = 2.75 | 7.40 8.37 alpha | A,Chisq | = 2.80 | 7.99 10.00 alpha | A,Chisq | = 2.85 | 8.58 12.12 alpha | A,Chisq | = 2.90 | 9.17 14.72 alpha | A,Chisq | = 2.95 | 9.74 17.76 alpha | A,Chisq | = 3.00 | 10.30 21.23

1395 days

Ev/day Error------ ----- 8.97 1.34 2.12 0.60 1.33 0.34 0.95 0.20 0.46 0.12 0.16 0.07 0.14 0.04

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Crab Spectrum Epochs 4-5

Fit Spectrum:

3.7x10-7 E-2.83±0.2

2 =10.3/5 d.o.f.

Crab Cyg Hot Spot Cyg Diffuse

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Andrew SmithMay 2006, Milagro Collaboration

Meeting

Crab Fit Results for Epochs 4-5alpha | A,Chisq | = 2.00 | 0.32 22.80 alpha | A,Chisq | = 2.05 | 0.38 22.04 alpha | A,Chisq | = 2.10 | 0.46 21.24 alpha | A,Chisq | = 2.15 | 0.54 20.40 alpha | A,Chisq | = 2.20 | 0.64 19.52 alpha | A,Chisq | = 2.25 | 0.76 18.62 alpha | A,Chisq | = 2.30 | 0.90 17.69 alpha | A,Chisq | = 2.35 | 1.06 16.74 alpha | A,Chisq | = 2.40 | 1.24 15.79 alpha | A,Chisq | = 2.45 | 1.44 14.84 alpha | A,Chisq | = 2.50 | 1.67 13.92 alpha | A,Chisq | = 2.55 | 1.93 13.05 alpha | A,Chisq | = 2.60 | 2.21 12.25 alpha | A,Chisq | = 2.65 | 2.51 11.55 alpha | A,Chisq | = 2.70 | 2.84 10.98 alpha | A,Chisq | = 2.75 | 3.18 10.57 alpha | A,Chisq | = 2.80 | 3.52 10.34 alpha | A,Chisq | = 2.85 | 3.87 10.33 --- Minimum alpha | A,Chisq | = 2.90 | 4.20 10.56 alpha | A,Chisq | = 2.95 | 4.51 11.03 alpha | A,Chisq | = 3.00 | 4.78 11.74

456 days

Ev/day Error ------ ----- 1.59 1.94 3.90 1.15 2.02 0.68 0.28 0.42 0.90 0.27 0.39 0.13

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Cygnus Hot Spot Spectrum

• Define Location of Cygnus Hot Spot as 73.5<glon<76.5 && -1.5<glat<1.5

• Also examine flux from the Cygnus region. Define the region as 65<glon<85 && -3<glat<+3 excluding the Cygnus Hot Spot contained within.

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Cygnus Spectrum Epochs 1-3

Hot Spot: alpha<<2.0 Poor FitDiffuse: (13.0 x 10-7) E-2.50±0.2 2 =14.4/5dof

Crab Cyg Hot Spot Cyg Diffuse

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Andrew SmithMay 2006, Milagro Collaboration

Meeting

Crab Fit Results for Epochs 1-3alpha | A,Chisq | = 2.00 | 0.38 29.35 | 4.00 19.35alpha | A,Chisq | = 2.05 | 0.41 29.78 | 4.61 18.51alpha | A,Chisq | = 2.10 | 0.45 30.21 | 5.30 17.72alpha | A,Chisq | = 2.15 | 0.48 30.62 | 6.06 16.97alpha | A,Chisq | = 2.20 | 0.51 31.02 | 6.89 16.30alpha | A,Chisq | = 2.25 | 0.54 31.41 | 7.79 15.71alpha | A,Chisq | = 2.30 | 0.56 31.77 | 8.74 15.22alpha | A,Chisq | = 2.35 | 0.58 32.11 | 9.76 14.83alpha | A,Chisq | = 2.40 | 0.59 32.43 | 10.82 14.56alpha | A,Chisq | = 2.45 | 0.60 32.71 | 11.91 14.42alpha | A,Chisq | = 2.50 | 0.60 32.97 | 13.01 14.39alpha | A,Chisq | = 2.55 | 0.59 33.21 | 14.12 14.50alpha | A,Chisq | = 2.60 | 0.57 33.41 | 15.21 14.73alpha | A,Chisq | = 2.65 | 0.55 33.58 | 16.27 15.09alpha | A,Chisq | = 2.70 | 0.52 33.73 | 17.28 15.55alpha | A,Chisq | = 2.75 | 0.49 33.85 | 18.21 16.12alpha | A,Chisq | = 2.80 | 0.45 33.95 | 19.05 16.79alpha | A,Chisq | = 2.85 | 0.41 34.03 | 19.80 17.53alpha | A,Chisq | = 2.90 | 0.37 34.10 | 20.43 18.34alpha | A,Chisq | = 2.95 | 0.32 34.14 | 20.94 19.20alpha | A,Chisq | = 3.00 | 0.28 34.18 | 21.31 20.11

Ev/day Error ------ ----- Hot Spot Diffuse 2.02 2.20 | 35.29 7.61 -2.67 0.97 | 9.74 3.36 0.63 0.55 | 1.87 1.91 -0.19 0.33 | 3.65 1.12 0.11 0.19 | 1.81 0.65 0.36 0.10 | 0.40 0.36 0.20 0.06 | 0.79 0.20

Hot Spot Diffuse

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Cygnus Spectrum Epochs 4-5

Hot Spot: (3.4x10-7) E-2.75±0.20 c2 = 2.8/5 d.o.f.Diffuse: (11.4x10-7) E-2.85±0.25 c2 = 4.1/ 5 d.o.f.

Crab Cyg Hot Spot Cyg Diffuse

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Andrew SmithMay 2006, Milagro Collaboration

Meeting

Cygnus Fit Results for Epochs 4-5alpha | A,Chisq | = 2.00 | 0.42 9.97 | 1.14 10.96alpha | A,Chisq | = 2.05 | 0.50 9.46 | 1.34 10.54alpha | A,Chisq | = 2.10 | 0.59 8.91 | 1.58 10.10alpha | A,Chisq | = 2.15 | 0.69 8.35 | 1.86 9.65alpha | A,Chisq | = 2.20 | 0.80 7.77 | 2.18 9.17alpha | A,Chisq | = 2.25 | 0.94 7.18 | 2.55 8.68alpha | A,Chisq | = 2.30 | 1.09 6.58 | 2.97 8.17alpha | A,Chisq | = 2.35 | 1.26 5.99 | 3.46 7.66alpha | A,Chisq | = 2.40 | 1.45 5.40 | 4.00 7.15alpha | A,Chisq | = 2.45 | 1.67 4.84 | 4.61 6.63alpha | A,Chisq | = 2.50 | 1.90 4.31 | 5.28 6.14alpha | A,Chisq | = 2.55 | 2.16 3.83 | 6.02 5.66alpha | A,Chisq | = 2.60 | 2.44 3.43 | 6.82 5.22alpha | A,Chisq | = 2.65 | 2.74 3.11 | 7.67 4.83alpha | A,Chisq | = 2.70 | 3.05 2.90 | 8.57 4.50alpha | A,Chisq | = 2.75 | 3.36 2.81 | 9.50 4.25alpha | A,Chisq | = 2.80 | 3.68 2.87 | 10.44 4.08alpha | A,Chisq | = 2.85 | 3.99 3.08 | 11.37 4.02alpha | A,Chisq | = 2.90 | 4.29 3.47 | 12.26 4.06alpha | A,Chisq | = 2.95 | 4.55 4.02 | 13.09 4.22alpha | A,Chisq | = 3.00 | 4.79 4.73 | 13.83 4.49

456 days

Ev/day Error ------ ----- Hot Spot Diffuse 8.73 3.29 | 24.23 11.32 1.54 1.83 | 12.90 6.39 2.99 1.08 | 2.85 3.74 1.01 0.67 | 3.98 2.33 0.78 0.42 | 3.62 1.46 0.50 0.26 | 1.83 0.92 0.72 0.20 | 1.58 0.68

Hot Spot Diffuse

Andrew SmithMay 2006, Milagro Collaboration

Meeting

Potential Systematic Errors• Confirmation of A4/X2 at high end?

Not enough MC data!

Very few hadrons simulated with high(x2,nfit) or A4!

Comparison of simulated hadrons and data.