Physics discussion ATLAS W exercise

19
Physics discussion ATLAS W exercise 01.03.2011 Konrad Jende Alpen LHC CMS A L I C E

description

Alpen. CMS. ALICE. Physics discussion ATLAS W exercise. LHC. 01.03.2011 Konrad Jende. Content. Measurement(s) Local combining Global combining More information / Links F.A.Q. Backup. Measurement(s). Structure of the Proton - PowerPoint PPT Presentation

Transcript of Physics discussion ATLAS W exercise

Page 1: Physics discussion ATLAS W exercise

Physics discussion ATLAS W exercise 01.03.2011

Konrad Jende

Alpen

LHC

CMS

ALICE

Page 2: Physics discussion ATLAS W exercise

2

1. Measurement(s)

2. Local combining

3. Global combining

4. More information / Links

F.A.Q.

Backup

Content

Page 3: Physics discussion ATLAS W exercise

3

1. Measurement(s)Structure of the Proton

What to measure? number of W events containing e+, e-, μ+, μ-

What to calculate? (only from quark-gluon interaction)

For what? Reveal structure of the proton

How? 1. Exercise: Identifying particles (e-, e+, μ+, μ- , Jets, Neutrinos) 2. Exercise: Identifying events (W+→e++ν, W+→ μ-+ν, W-→e-+ν, W-→ μ-+ν + BG)

3. Measurement: a) students will be split up in 20 groups b) each group analyzes 50 events

c) signal (W) vs. background events (electric charge of the leptons in case of signal) d) document results by using tally sheets 4. local combining – explanations how students can derive statements about the

inner structure of the proton from this measurement (5. global combining – comparison of the ratios)

Learning Objectives? • students proof the valence quark structure of the proton by doing a measurement of a physics observable

• interpret this measurement and get basic insights from it using theoretical/phenomenological arguments [for details look at the document: Aims of

Particle Physics Masterclasses by Michael Kobel]

W-Path

Single W (Structure of the

Proton)

WW-Pairs (Search for the

Higgs)

sW' charged negatively of numbersW' charged positively of number

:R

Page 4: Physics discussion ATLAS W exercise

5

1. Measurement(s)

Search for new physics (Higgs search)

What to do? Search for simulated Higgs events

For what? Identify events where a Higgs decayed into WW

How? 1. Measurement: Find those events in the data samples! Document it on the tally sheet by noting the event number

2. local combining – discussions of chosen events 3. global combining – discussions of chosen events

Learning Objectives? • identify events which would be candidates for new physics and qualitatively understand pre-conditions for claiming a discovery

W-Path

Single W (Structure of the

Proton)

WW-Pairs (Search for the

Higgs)

Page 5: Physics discussion ATLAS W exercise

6

2. Local Combining

N = 0Positron

e+Electron

e-Antimuon

μ+Muon

μ-

A

B C D E F G H I J K L

M N O P Q R S

T

Total 0 0 0 0 0 0

0 0

#DIV/0! #DIV/0!

ratio N = 0

Total 604 403 656 425

Total W+/W- number W+ 1260 number W- 828

Verhältnis ATLAS

Total W+/W- number W+ number W- number W++W- 0

#DIV/0!

1,52

20 g

roup

s ana

lyze

50

even

ts e

ach

Anal

yse

der M

essu

ng

W → ... + νBackground

Events

com

paris

on w

ith A

TLAS

*

|W+|/|W-|

WW

|W+|/|W-|

1. Each group has to fill in its result.2. Students can compare their

measurement (of the ratio of the number of positively charged W’s to the number of

negatively charged W’s) with one of ATLAS (data taken from: Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector Authors: The ATLAS Collaboration (Submitted on 11 Oct 2010)

3. Revealing the proton structure with that ratio is pretty hard – that is why we have to bring some theory into play

Page 6: Physics discussion ATLAS W exercise

7

3. Global combining

Physics discussion at Videoconference - general facts and proton structure measurement

Where takes it place? EVO + EditGrid : http://www.editgrid.com/user/masterclass/Analysis_All Online-spreadsheet, no password is needed, only input cells are editablevenues will enter their numbers after completing their measurement (at ca. 3:30pm on a certain MC day)

What are you 1. Compare the “raw” ratio (usually about 1.4 – 1.6) among all venuessupposed to do?

2. Combine the “raw” ratios and compare with the first ATLAS results

3. Discuss the corrected ratios

4. Always Remember: If you get very good answers of students or you see that they reached good results, do not forget to praise their work!

5. Do not repeat too much (that was already done locally)

Which tools help? ATLANTIS Event Display (MINERVA), Events, Website

Page 7: Physics discussion ATLAS W exercise
Page 8: Physics discussion ATLAS W exercise

9

3. Global combining

Physics discussion at Videoconference - Higgs events

How to discuss the 1. You should know which events are the hidden simulated HWW events!Possible Higgs 2. The venues will send the event numbers of their candidate events. Chose for examplecandidate events? two events (one that isn’t a Higgs, one that is a Higgs).(recommendation) 3. Use the Shared Desktop option by EVO to show your computer screen.

4. Start MINERVA, read the two events (you may copy them into a folder to more easily present) and show them.5. Ask the speaker of the venue that proposed these events why they thought this was a Higgs event.6. Make clear why in your opinion an event is or is not a possible Higgs candidate.7. You could also use the MINERVA demonstration mode to animate the collision event (Event – Animated event; set up PT cut before)8. After finishing the discussion about the particular events tell them a little bit more about discoveries in your experiment (not only Higgs) and their claiming

Which tools help? ATLANTIS Event Display (MINERVA), Events, Website

Page 9: Physics discussion ATLAS W exercise

10

4. More information / Links

Website with information on the W measurement: www.cern.ch/kjende/en/wpath.htm

Details on the pre-selection of the ATLAS data, instructions how to use both website as well as the Event Display MINERVA: www.cern.ch/kjende/en/documentation2.htm

If you have further questions do not hesitate to contact me:[email protected] – 3-R-006 at CERN

Page 10: Physics discussion ATLAS W exercise

11

F.A.Q.

www.cern.ch/kjende/en/documentation2.htm

Page 11: Physics discussion ATLAS W exercise

12

Backup

Aims of Particle Physics Masterclasses (by Michael Kobel)

Local Combining: Tally sheet

Local Combining: extra stuff about development of the ratio R± and ist uncertainty

Page 12: Physics discussion ATLAS W exercise

13

Learning Objectivs Aims of Particle Physics Masterclasses 1: On a basic Level: Students should (e.g. via lectures)

be *informed* (not taught) about general topics of current research in high energy particle physics (hep), central findings of hep research in last ~30 years, (standard model, building blocks, forces, charges,…), status and aims of current experiments (LHC, …)get insight in the way hep research is organized in international collaborations, in dialogue/exchange of experiment and theory , wrt. methods of discovery of new phenomena, (counting methods, perhaps mass peaks, etc.)

Students should *learn* themselves toidentify different particles via their pattern in detectorscategorize events of LHC in pre-defined final statesunderstand the concept of signal and bachgrounddo a measurement of a physics observable (LHC W-path: ratio of W+ / W- ) interpret this measurement and get basic insights from it using theoretical/phenomenological arguments ( proton structure, …)identify events which would be candidates for new physics and qualitatively understand pre-conditions for claiming a discovery (e.g. WW or ZZ events as Higgs candidates, 3 lepton events as SUSY candidates)

Page 13: Physics discussion ATLAS W exercise

14

Learning Objectivs Aims of Particle Physics Masterclasses 2: Get the feeling that they:

understand the basic principles how particles are identified, are able to perform themselves some of the measurements, which the scientists currently do, on a somewhat simplified levelare able to draw conclusions from these measurements

get the impression thattopics of fundamental research in natural science are interesting its results are relevant as cultural knowledge of mankind

Page 14: Physics discussion ATLAS W exercise

16

2. Local Combining

N = 0Positron

e+Electron

e-Antimuon

μ+Muon

μ-

A

B C D E F G H I J K L

M N O P Q R S

T

Total 0 0 0 0 0 0

0 0

#DIV/0! #DIV/0!

ratio N = 0

Total 604 403 656 425

Total W+/W- number W+ 1260 number W- 828

Verhältnis ATLAS

20 g

roup

s ana

lyze

50

even

ts e

ach

Anal

yse

der M

essu

ng

W → ... + νBackground

Events

com

paris

on w

ith A

TLAS

*

|W+|/|W-|

WW

|W+|/|W-|

Total W+/W- number W+ number W- number W++W- 0

#DIV/0!

1,52

1. Each group has to fill in its result.2. Students can compare their

measurement (of the ratio of the number of positively charged W’s to the number of

negatively charged W’s) with one of ATLAS (data taken from: Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector Authors: The ATLAS Collaboration (Submitted on 11 Oct 2010)

3. Revealing the proton structure with that ratio is pretty hard – that is why we have to bring some theory into play

Page 15: Physics discussion ATLAS W exercise

17

2. Local Combining

N = 999Positron

e+Electron

e-Antimuon

μ+Muon

μ-

A 3 4 5 3 35B 7 5 5 2 31 C 2 3 9 2 33 D 4 2 4 6 34 E 4 3 5 4 34 F 5 7 7 2 29 G 7 1 2 3 37 H 4 2 9 4 31 I 5 1 7 3 34 J 2 4 5 5 34 K 4 3 2 2 39 L 5 2 5 4 34

M 6 6 1 4 33 N 6 2 7 1 34 O 7 3 7 1 32 P 4 6 7 0 33 Q 4 8 5 3 30 R 8 0 6 4 32 S 2 5 2 3 38T 7 6 3 1 33

Total 96 73 103 57 670 0

199 130

60,5 39,5

ratio N = 999

Total 604 403 656 425

Total W+/W- number W+ 1260 number W- 828

Verhältnis ATLAS

Total W+/W- number W+ number W- number W++W- 329

1,53

1,52

20 g

roup

s ana

lyze

50

even

ts e

ach

Anal

yse

der M

essu

ng

W → ... + νBackground

Events

com

paris

on w

ith A

TLAS

*

|W+|/|W-|

WW

|W+|/|W-|

1. Each group has to fill in its result.2. Students can compare their

measurement (of the ratio of the number of positively charged W’s to the number of

negatively charged W’s) with one of ATLAS (data taken from: Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector Authors: The ATLAS Collaboration (Submitted on 11 Oct 2010)

3. Revealing the proton structure with that ratio is pretty hard – that is why we have to bring some theory into play

Numbers in the spreadsheet taken from own research

Page 16: Physics discussion ATLAS W exercise

18

2. Local Combining

4. Work out the fraction of gluon-gluon interaction for W+ and W-!5. Work out the fraction of quark-gluon interaction for W+ and W- by forming the sum

of the first column! 6. Forming the ratio of the number of positively charged W’s to the number of

negatively charged W’s and LET THE STUDENTS INTERPRET ITS RESULT!

quark-gluon interaction 66,0

gluon-gluon interaction 34,0

measurement result in % 60,5 39,5 100,0

R± (quark-gluon interaction)

Theory: fraction in %

#DIV/0!

interaction processes Number W+ Number W-

Page 17: Physics discussion ATLAS W exercise

19

2. Local Combining

4. Work out the fraction of gluon-gluon interaction for W+ and W-!5. Work out the fraction of quark-gluon interaction for W+ and W- by forming the

sum of the first column! 6. Forming the ratio of the number of positively charged W’s to the number of

negatively charged W’s and LET THE STUDENTS INTERPRET ITS RESULT!

quark-gluon interaction 66,0

gluon-gluon interaction 17,0 17,0 34,0

measurement result in % 60,5 39,5 100,0

R± (quark-gluon interaction)

Theory: fraction in %

#DIV/0!

interaction processes Number W+ Number W-

Page 18: Physics discussion ATLAS W exercise

20

2. Local Combining

4. Work out the fraction of gluon-gluon interaction for W+ and W-!5. Work out the fraction of quark-gluon interaction for W+ and W- by forming the sum

of the first column! 6. Forming the ratio of the number of positively charged W’s to the number of

negatively charged W’s only from quark-gluon interaction and LET THE STUDENTS INTERPRET THEIR RESULT!

quark-gluon interaction 43,5 22,5 66,0

gluon-gluon interaction 17,0 17,0 34,0

measurement result in % 60,5 39,5 100,0

R± (quark-gluon interaction)

Theory: fraction in %

1,93

interaction processes Number W+ Number W-

Page 19: Physics discussion ATLAS W exercise

21

2. Local CombiningGruppe R± Unsicherheit

A 1,22 0,97A-B 1,73 0,95A-C 2,14 1,03A-D 1,76 0,70A-E 1,70 0,60A-F 1,67 0,52A-G 1,81 0,54A-H 1,97 0,56A-I 2,18 0,60A-J 1,93 0,49A-K 1,88 0,46A-L 1,91 0,45

A-M 1,72 0,38A-N 1,91 0,42A-O 2,09 0,45A-P 2,12 0,44A-Q 1,95 0,38A-R 2,09 0,41A-S 1,94 0,36A-T 1,93 0,35

Extra stuff:

development of R± and its uncertainty depending on the absolute number of analyzed events