This document summarizes Sho Iwamoto's lunch seminar on studying supersymmetry (SUSY) at the LHC without assuming R-parity conservation. Iwamoto explains that most LHC studies assume R-parity conservation, which results in stable lightest supersymmetric particles (LSP) and missing energy signals. However, if R-parity is violated, the LSP would decay and the missing energy signal would disappear, making SUSY significantly more difficult to detect at the LHC. Iwamoto is interested in studying what LHC events and signals might look like if R-parity is violated. He presents one past study that examined R-parity violation in the context of the minimal supergravity (m

1. SUSY@LHC
without R-Parity
岩本 祥 [Sho Iwamoto]
2009/06/08
Lunch Seminar @ UT/Hongo
B. C. Allanach et al.
R-Parity violating minimal supergravity at the LHC
arXiv: 0710.2034 [hep-ph]

2. Contents
1. SUSY and R-Parity
2. Other ways
3. What I’m studying
4. Why not Explored?
5. Exemplary Study
(if we have time, that is,
if I’m not trapped anywhere.)
B. C. Allanach et al.
R-Parity violating minimal supergravity at the LHC
arXiv: 0710.2034 [hep-ph]
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <2>

3. 1. SUSY and R-Parity
 SUSYだと陽子崩壊が起きるから
R-Parityを課すのがいいよ。
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <3>

4. SUSY and R-parity
 Standard Model (SM)
› VERY NICE theory!!
› But has some problems…. such as
 Hierarchy problem, Neutrino mass, ….
→ The most hopeful theory is…..
 SUSY (or Models with supersymmetry)
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <4>

5. SUSY and R-parity
But SUSY also has some problems.
› Many Particles (do they exist?),
› Many Models (How to break SUSY?),
› Many Parameters (Real values are…?)
And furthermore,
Proton decays!!!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <5>

6. Proton decay @ MSSM
Under MSSM (Minimal Supersymmetric Standard Model),
we have following interactions:
And then……
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <6>

7. Proton decay @ MSSM
Proton decays!!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <7>

8. Proton decay @ MSSM
( i, j, k for generations.)
Unreasonably constrained!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <8>

9. SUSY and R-parity
 Howshould we do?
→ Review the Standard Model case.
 Why does not proton decay under SM?
→ Because
Baryon number B and Lepton Number L
are accidentally conserved.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <9>

10. Proton decay @ SM
Under SM, 湯川 interactions are only
and their Hermitian conjugates.
→ B and L are accidentally conserved
by the gauge symmetry.
→ Proton decay, e.g. , is forbidden.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <10>

11. Proton decay @ SM
 Roughly speaking,
Proton decay, such as
is B-/L-violating process.
 Therefore,
“Protect B and L as SM”
may be a good solution.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <11>

12. Proton decay @ MSSM B nor L!
MSSM conserves neither
However, under SUSY models,
possible interactions are:
( B / L conserving )
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <12>

13. SUSY and R-parity
 We want to omit
these B/L-breaking terms.
→ We introduce R-Parity.
( s : spin )
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <13>

14. SUSY and R-parity
 R-Parity forbids these interactions.
→ B/L are conserved again!
→ Proton become stable again!!!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <14>

15. SUSY and R-parity
 And as you know, since
R-Parity makes LSP stable,
(Lightest Supersymmetric Particle)
∴ LSP → a Candidate
for Dark Matter!!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <15>

16. 2. Other Ways
 でも実はR-Parityじゃない対称性
でもいいよ
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <16>

17. Other ways
 But Why R-Parity?
› Evidence for R-Parity conserving?
› No other symmetry can prohibit
Proton Decay?
… Actually we don’t have to
BELIEVE R-Parity conservation.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <17>

18. Proton decay @ MSSM
 Roughly speaking,
Proton Decay needs
both B-violating and L-violating term.
B L
More precise?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <18>

19. Proton decay @ MSSM
 Roughlyprecisely,
 Or a bit speaking,
Proton Decay needs
Proton decay doesn’t occur if
both B-violating and L-violating term.
• Baryon number is conserved
OR
• (Lepton number is conserved
and B L)
More precise?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <19>

20. Other ways
 Thereforewe can easily find
“other ways.”
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <20>

21. Other ways
L-violate B-violate
 Baryon Parity
› Proton → not decay Good!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <21>

22. Other ways
L-violate B-violate
 Lepton Parity
› Proton → not decay if Good!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <22>

23. Other ways
L-violate B-violate
 R-Parity
› Proton → not decay Good!
› LSP → can be DM Lucky!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <23>

24. Other ways
 That is,
we can ADD
B- or L-violating interactions!!
[Example]
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <24>

25. Other Ways
NOTE
◊ From a practical viewpoint,
“Which symmetry is installed?”
is a secondary concern.
◊ What is important is
“Which terms are
in Lagrangian?”
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <25>

26. 3. What I’m studying
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <26>

27. What I’m studying
By the way,
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <27>

28. What I’m studying
almostALL
studies on LHC
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <28>

29. What I’m studying
is assuming
R-Parity
conservation.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <29>

30. What I’m studying
However, as we’ve seen,
We can violate
R-Parity!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <30>

31. What I’m studying
 R-Parity violation introduce
additional
interactions
to the Lagrangian.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <31>

32. What I’m studying
 Therefore if R-Parity is violated,
we will observe
different
LHC event
from R-Parity conserving case.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <32>

33. What I’m studying
Then, if R-parity is violated,
What will
happen in LHC?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <33>

34. What I’m studying
Then, if R-parity is violated,
What will
happen in LHC?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <34>

35. What I’m studying
Therefore
I’m interested in
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <35>

36. What I’m studying
LHC study
without
R-Parity.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <36>

37. What I’m studying
Why is this theme
But
not explored?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <37>

38. What I’m studying
some
Is there
PROBLEM?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <38>

39. 4. Why not explored?
 R-Parityを仮定しないと，LHCで
のSUSY eventの検出がとてもむ
つかしくなるから。
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <39>

40. Why not explored?
 If R-parity is conserved…
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <40>

41. Why not explored?
 If R-parity is conserved…
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <41>

42. Why not explored?
 If R-parity is conserved…
jet
jet
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <42>

43. Why not explored?
 If R-parity is conserved…
jet
Created in pair!
jet
Then…
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <43>

44. Why not explored?
we can’t observe!
(e.g. )
Therefore
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <44>

45. Why not explored?
Here, These LSPs are NOT observed!!!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <45>

46. Why not explored?
Here, These LSPs are NOT observed!!!
→ Momentum seems to be
NOT conserved.
→ Large “Missing Energy”
This would be a good SUSY signal.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <46>

47. Why not explored?
 However,if R-Parity is not
conserved,
LSP DOES
DECAY!!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <47>

48. Why not explored?
Observable!
Therefore
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <48>

49. Why not explored?
Here, These LSPs are NOT observed!!!
→ Momentum seems to be
NOT conserved.
→ Large “Missing Energy”
This would be a good SUSY signal.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto
[Lunch Seminar] SUSY ( 2009/06/08 ) )
2010/02/11 <49>

50. Why not explored?
No more
“Large ”
signal
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <50>

51. Why not explored?
 Thenhow can we “detect”
SUSY in LHC-experiment?
This is what I want to study!
 …… It is “case by case.”
 So,SUSY/LHC without R-Parity
is difficult.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <51>

52. 5. Exemplary Study
 この分野での過去の研究を紹介
します。
B. C. Allanach et al.
R-Parity violating minimal supergravity at the LHC
arXiv: 0710.2034 [hep-ph]
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <52>

53. Exemplary Study
 SUSY model : mSUGRA
 R-parity : Broken
 LSP :
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <53>

54. Now STAU is LSP.
 If R-parity is conserved,
LSP = DM must be neutral.
Since DM must be neutral
for cosmological reason.
(which I don’t know well)
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <54>

55. Now STAU is LSP.
 But if no R-parity, then
LSP can be charged, and…
Large parameter
region is
NOW OPEN!!
Ｂ
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <55>

56. Exemplary Study
 Then,
what is observed in LHC?
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <56>

57. Exemplary Study
 The paper discussed
case & case.
 But today we focus only on
case.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <57>

58. Exemplary Study
case
 Only is available, i.e.
Parameters
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <58>

59. [Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <59>

60. case
 LSP will decay into 4-leptons.
[Example]
 NLSP will decay as
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <60>

61. case
 Simulation Result
Events with sparticle pair production are:
•Each event is acompanied by 2-4 jets.
•Total cross section is .
(100-1000events per year @ LHC’s best)
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <61>

62. case
Features:
 Simulation Result
•Multi lepton final state (≧4)
•Multi tau final state (≧4, in general)
Events with sparticle pair production are:
•Missing energy (from neutrinos)
•Each event is acompanied by 2-4 jets.
•Total cross section is .
(100-1000events per year @ LHC’s best)
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <62>

63. case
 Key point
› Many s → Identification of is
important for LHC!
is observed as jet, and
› Few jets (2-4) → Not so difficult to identify.
And also
› is also a good sign, because…
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <63>

64. case
 Key point
› Many s → Identification of is
important for LHC!
is observed as jet, and
› Few jets (2-4) → Not so difficult to identify.
And also
› is also a good sign, because…
Peak of is lower than LSP-missing.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <64>

65. case
 Conclusion
In this case,
› Multi tau
› Multi lepton
› (but not so large as O(100) GeV )
are good signs of SUSY events.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <65>

66. case
But really?
 We can really distinguish tau-jets?
 No Backgrounds?
(i.e. Aren’t similar final states created by SM events?)
 Detector simulation!
 How about on other parameter points?
→ Need improvement!
(or more detailed analysis.)
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <66>

67. That’s all.
Thank you
for listening.
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <67>

68. Appendix
 Superpotential

69. Hierarchy Problem
 In Standard Model with Higgs,
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <69>

70. Hierarchy Problem
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <70>

71. Hierarchy Problem
 In MSSM (or other SUSY models),
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <71>

72. Hierarchy Problem
And its superpartner goes round!
Cancelled!
[Lunch Seminar] SUSY@LHC without R-Parity / Sho Iwamoto ( 2009/06/08 ) <72>