Double parton interactions in + 3 jets events in p...

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γ γ ¯ = .

Transcript of Double parton interactions in + 3 jets events in p...

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Double parton interactions in γ + 3 jets events

in pp̄ collisions at√s = 1.96 TeV in CDF

Giorgia Rauco

Fermilab, CDF

Summer Internship 2013

Supervisor:

Raymond L CulbertsonTutor:

Alessandra Lucà

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 1 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Outline

1 Introduction and DPI theory

2 Kinematics of γ + 3 jets events

3 Discriminating variables

4 Data results

5 Montecarlo simulations

6 Summary

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 2 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Outline

1 Introduction and DPI theory

2 Kinematics of γ + 3 jets events

3 Discriminating variables

4 Data results

5 Montecarlo simulations

6 Summary

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 2 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Outline

1 Introduction and DPI theory

2 Kinematics of γ + 3 jets events

3 Discriminating variables

4 Data results

5 Montecarlo simulations

6 Summary

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 2 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Outline

1 Introduction and DPI theory

2 Kinematics of γ + 3 jets events

3 Discriminating variables

4 Data results

5 Montecarlo simulations

6 Summary

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 2 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Outline

1 Introduction and DPI theory

2 Kinematics of γ + 3 jets events

3 Discriminating variables

4 Data results

5 Montecarlo simulations

6 Summary

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 2 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Outline

1 Introduction and DPI theory

2 Kinematics of γ + 3 jets events

3 Discriminating variables

4 Data results

5 Montecarlo simulations

6 Summary

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 2 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Introduction

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 3 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Introduction

Single Parton Collision

One partonic scattering in oneproton-antiproton collision

Double Parton Collision

Two indipendent partonicscatterings in oneproton-antiproton collision

Final state of DPI: γ+jet and dijet

The �rst analysed was performed by UA2 in 1991

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 4 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Introduction

How?

γ + 3 jets events∫L dt = 9.5 fb−1

pp̄ collisions at√s = 1.96

TeV

Why?

to determine the fraction of the DPI in a single pp̄ collision

to make accurate estimation of background for many rare

new physics processes

QCD studies

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 5 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Introduction

How?

γ + 3 jets events∫L dt = 9.5 fb−1

pp̄ collisions at√s = 1.96

TeV

Why?

to determine the fraction of the DPI in a single pp̄ collision

to make accurate estimation of background for many rare

new physics processes

QCD studies

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 5 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Kinematics

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 6 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Kinematics of γ + jets events:

Multiplicities

Figure: Multiplicities of photons and jets depending on their energy, in

linear and log scale

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 7 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Kinematics of γ + jets events:

angular distributions

Figure: Azimuthal angle and pseudorapidity distributions for the γ and for

the leading jet, as a function of their energy

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 8 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Kinematics of γ + jets events:

energy distributions

Figure: Energy distributions for the γ and for the leading jet

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 9 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discrimination beetweenDPI and SPI

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 10 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discriminating variables

D0 Collaboration, arXiv:0912.5104v2 [hep-ex]

Discriminating DPI from SPI

Try to exploit the back-to-back nature of the objects coming fromSPI events

∆S = ∆φ( ~pT (γ, i), ~pT (j , k)) (1)

In the γ + 3 jet analysis,

the i , j and k objects are

chosen such as to minimize

the pT imbalance

In this way, it is possible to

split the γ + 3 jet into

γ+ jet and dijet pairs

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 11 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discriminating variables

The two object pairs are found by minimizing three other

variables with respect to the jet index:

SpT =1√2

√(| ~pT (γ, i)|δpT (γ, i)

)2

+

(| ~pT (j , k)|δpT (j , k)

)2

(2)

Sp′T

=1√2

√√√√√( | ~pT (γ, i)|| ~pγT | + | ~pi

T |

)2

+

| ~pT (j , k)|

| ~pjT | + | ~pk

T |

2

(3)

Sφ =1√2

√(∆φ(γ, i)

δφ(γ, i)

)2

+

(∆φ(j , k)

δφ(j , k)

)2

(4)

where ∆φ(γ, i) = |π − φ(γ, i)|

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 12 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discriminating variables

The two object pairs are found by minimizing three other

variables with respect to the jet index:

SpT =1√2

√(| ~pT (γ, i)|δpT (γ, i)

)2

+

(| ~pT (j , k)|δpT (j , k)

)2

(2)

Sp′T

=1√2

√√√√√( | ~pT (γ, i)|| ~pγT | + | ~pi

T |

)2

+

| ~pT (j , k)|

| ~pjT | + | ~pk

T |

2

(3)

Sφ =1√2

√(∆φ(γ, i)

δφ(γ, i)

)2

+

(∆φ(j , k)

δφ(j , k)

)2

(4)

where ∆φ(γ, i) = |π − φ(γ, i)|

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 12 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discriminating variables

The two object pairs are found by minimizing three other

variables with respect to the jet index:

SpT =1√2

√(| ~pT (γ, i)|δpT (γ, i)

)2

+

(| ~pT (j , k)|δpT (j , k)

)2

(2)

Sp′T

=1√2

√√√√√( | ~pT (γ, i)|| ~pγT | + | ~pi

T |

)2

+

| ~pT (j , k)|

| ~pjT | + | ~pk

T |

2

(3)

Sφ =1√2

√(∆φ(γ, i)

δφ(γ, i)

)2

+

(∆φ(j , k)

δφ(j , k)

)2

(4)

where ∆φ(γ, i) = |π − φ(γ, i)|

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 12 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discriminating variables

We plotted the three variables and the three jets combinations.

SpT distribution Sp′T

distribution Spφ distribution

Observation

Good separation between the plots of the pair (γ, jet 0) and theremaining two.

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 13 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Discriminating variables

We plotted the three variables and the three jets combinations.

SpT distribution Sp′T

distribution Spφ distribution

Observation

Good separation between the plots of the pair (γ, jet 0) and theremaining two.

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 13 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Data results

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 14 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Data results

We plotted the index of the jet associated to the γ which

minimizes the three variables.

Result

The best pairs combination is (γ, jet 0) and (jet 1, jet 2).

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 15 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Data results

We plotted the index of the jet associated to the γ which

minimizes the three variables.

Result

The best pairs combination is (γ, jet 0) and (jet 1, jet 2).

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 15 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Data results

∆S = ∆φ( ~pT (γ, 0), ~pT (1, 2)) (5)

with the pairs obtained based on the best pairwise balance

Result

The tail between 0 and 1.5 is relatively �at → Evidence for DPI

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 16 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Data results

This is constistent with the theoretical hyphotesis:

SPI

distribution ∆S should peak at π and should show a tail due to

the radiation

DPI

distribution ∆S alone should be relatively �at

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 17 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Montecarlo

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 18 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Montecarlo results

∆SpT distribution ∆Sp′T

distribution ∆Spφ distribution

evidence of the tail

- relatively �at for DPS- with a light slope due to the radiation for SPS

DPI samples bigger than SPI sample (SPS has no MPI)

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 19 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Montecarlo results

∆SpT distribution ∆Sp′T

distribution ∆Spφ distribution

evidence of the tail

- relatively �at for DPS- with a light slope due to the radiation for SPS

DPI samples bigger than SPI sample (SPS has no MPI)

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 19 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 20 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

the best pair combination for the �nal state is (γ, jet 0)and (jet 1, jet 2)

evidence for DPI thanks to the low sided tail in the ∆S plot

What is next?

found the fraction of DPI using both Montecarlo and data

obtain the DPI cross section

To be continued...

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 21 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

the best pair combination for the �nal state is (γ, jet 0)and (jet 1, jet 2)

evidence for DPI thanks to the low sided tail in the ∆S plot

What is next?

found the fraction of DPI using both Montecarlo and data

obtain the DPI cross section

To be continued...

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 21 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

the best pair combination for the �nal state is (γ, jet 0)and (jet 1, jet 2)

evidence for DPI thanks to the low sided tail in the ∆S plot

What is next?

found the fraction of DPI using both Montecarlo and data

obtain the DPI cross section

To be continued...

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 21 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

the best pair combination for the �nal state is (γ, jet 0)and (jet 1, jet 2)

evidence for DPI thanks to the low sided tail in the ∆S plot

What is next?

found the fraction of DPI using both Montecarlo and data

obtain the DPI cross section

To be continued...

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 21 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

the best pair combination for the �nal state is (γ, jet 0)and (jet 1, jet 2)

evidence for DPI thanks to the low sided tail in the ∆S plot

What is next?

found the fraction of DPI using both Montecarlo and data

obtain the DPI cross section

To be continued...

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 21 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Conclusions

the best pair combination for the �nal state is (γ, jet 0)and (jet 1, jet 2)

evidence for DPI thanks to the low sided tail in the ∆S plot

What is next?

found the fraction of DPI using both Montecarlo and data

obtain the DPI cross section

To be continued...

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 21 / 22

DoubleParton

Interactions

GiorgiaRauco

Outline

Introduction

Kinematicsof γ + jetsevents

Discriminatingvariables

Data results

Montecarlo

Conclusions

Acknowledgement

Raymond L Culbertson &

Costas Vellidis

Alessandra Lucà

Simone Donati &

Giorgio Bellettini

Italian Summer Students

Giorgia Rauco (CDF) Double Parton Interactions Summer Internship 2013 22 / 22