Download - Physics discussion ATLAS W exercise
Physics discussion ATLAS W exercise 01.03.2011
Konrad Jende
Alpen
LHC
CMS
ALICE
2
1. Measurement(s)
2. Local combining
3. Global combining
4. More information / Links
F.A.Q.
Backup
Content
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
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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)
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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
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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
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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
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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
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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
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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)
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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
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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
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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
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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-
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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-
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-
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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