# Document 11541209

```Obligatory Assignment II
10.04.2013 to be delivered by 21.04.2015 @ 15:15 Farid Ould-&shy;‐Saada 06/04/15
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Important remarks &sect;  In answering the following questions, use as much as possible your own reasoning, alternative methods, … &sect;  Once you have delivered the assignment some students might be asked to solve one question each in front of the class &iexcl;
Compulsory assignments &sect;  It is necessary to deliver all assignments and get them approved ▪  to be qualiﬁed for the ﬁnal exam ▪  to have CERN travel expenses (partly covered) 08/04/15
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2.
In the LHC at CERN, 2 proton beams will head-&shy;‐on with energies Ep=13TeV. a)
What is the centre of mass (CM) energy? b)
What energy would be needed to produce the same CM energy with a proton beam on a ﬁxed hydrogen target? c)
How does this energy compare with cosmic ray energies? d)
Referring to supplement 1.1 “Cosmic rays and astroparticle physics” and to the CERN visit made to AMS, what is th emain outcome of the AMS experiment? The neutral pion decays to two photons (π0 &agrave; γγ) with a branching ratio of 98.8%. a)
What is the minimum opening angle between the photons for a pion with momentum 100 GeV? mπ0=135 MeV. b)
Compare to a Higgs boson of similar momentum and decay H&agrave; γγ. mΗ=125 GeV. 06/04/15
http://arxiv.org/pdf/astro-ph/0607109v2.pdf
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1.  Which of the following reactions are allowed and which are forbidden? -&shy;‐ If allowed, draw the Feynman graph and state which interac8on is at work. -&shy;‐ If forbidden, give the reasons. 1. K − p → K +Ξ−
2. π 0 → γ e+e−
3. ρ 0 → γγ
4. Ω− → Ξ0 π −
5. n → pπ −
6. e+e− → e+e−
+
+ −
7.
ν
p
→
τ
n
8.
e
e → qqg
τ
9. &micro; + → e+ν eν &micro; e+e−
10. gg → gg
11. ν ee− → ν ee−
12. e+e− → W +W −γ
13. ν eν e → ν eν e
14. gg → H → γγ
06/04/15
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Solve the following exercises (Braibant et al. problems book) &sect;  6.6, 7.6, 7.7, 7.11, 7.13, 7.17 &iexcl;
Based on the lectures on heavy ion physics during the CERN visit &sect;  Explain what is quark-&shy;‐gluon plasma (QGP), &sect;  Give 2 possible experimental evidences for QGP 06/04/15
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