Status of GMSB studies
-
Upload
lareina-giles -
Category
Documents
-
view
19 -
download
1
description
Transcript of Status of GMSB studies
![Page 1: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/1.jpg)
Status of GMSB studies
Shilei Zang
University of Colorado, Boulder
CU CMS Meeting, 28th Apr. 2008
![Page 2: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/2.jpg)
2
Outline
• Invariant mass of neutralino
• De-convolution method
G~~0
1
![Page 3: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/3.jpg)
3
G~
01
~
01
~
p p
q
q
q
q ~…
…
jet
jet
jet
jet
G~
~
• MET distribution is used to get signal yield, but we have two gravitinos.
21 METMETMET
MET
![Page 4: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/4.jpg)
4
• MET distribution is used to get signal yield. Simple variable; powerful separation; largely used• 1) It’s crowded at small MET region for both signal and
background.• 2) Shapes are different for signal and each bkg.• 3) Vector addition of the two gravitinos.• 4) MET resolution is difficult to estimate.• 5) Can not get mass from MET MET is not a much sensitive variable; bkg studies are
difficult; not directly relate with mass
Can we use the invariant mass of photon+gravitino?
![Page 5: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/5.jpg)
5
)]())()(()))(()([(2
))]~
()~
(())()((
))~
()~
())(()([(24
2121
2121
21212
METppMETEE
GpGppp
GEGEEEmass
TT
2/)]())()(()))(()([(~ 2121 METppMETEEmass TT
G~~0
1 )]
~()()
~()([2
);~
(),~
();(),(:~);
~(),
~();(),(:~
2
22220
1
11110
1
GppGEEmass
GpGEpE
GpGEpE
![Page 6: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/6.jpg)
6
• MET
• Pt2>0GeV
• Peak=157 GeV
• MET
• Pt1>90GeV; Pt2>30GeV
• Peak=160.4 GeV;
MET
![Page 7: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/7.jpg)
7
• Pt2>0GeV
• Peak=185GeV
• Sig=77GeV
• Pt1>90GeV; Pt2>30GeV; MET>130GeV
• Peak=223GeV; sig=61GeV
2/)]())()(()))(()([(~ 2121 METppMETEEmass TT
• Pt1>90GeV; Pt2>30GeV;
• Peak=196GeV
Invariant mass of neutralino
![Page 8: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/8.jpg)
8
two gravitinos.photon and gravitino.
photon1 and gravitino2 photon2 and gravitino1
• Cos(theta) from MC Truth G~~0
1
![Page 9: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/9.jpg)
9
• Cos(theta) of and .)()( 21 TT pp
MET
2/)]())()(()))(()([(~ 2121 METppMETEEmass TT
![Page 10: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/10.jpg)
10
• Ratio = (-cos(theta))/cos(theta)
2/)]())()(()))(()([(~ 2121 METppMETEEmass TT
2/)]())()(()))(()([(~2 2121 METppMETEEmass TT
-cos(theta)
cos(theta)
-cos(theta)
cos(theta)
![Page 11: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/11.jpg)
11
mass mass2
mass2 weighted
mass minus
mass2 weighted
• mass = CB Line; mass2weighted = CB Line + Polynomial
• mass = mass2weighted for background
![Page 12: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/12.jpg)
12
Variables for GMSB analysis
I. MET
II. Rough mass of neutralino
III. Edge of MT2 distribution
IV. Edges of some invariant masses
V. Accurate calculation with cross-events for long decay chain
VI. Long-lived neutralinos: photon timing, cluster shapes, decay chain, .. (CDF, ATLAS, CMS)
VII. Deconvolution method accurate mass of neutralino; accurate ctau of neutralino
hep-ph/9906349
CMS Note1997/079
arXiv:0802.4290v1
![Page 13: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/13.jpg)
13
2/)]())()(()))(()([(~ 2121 METppMETEEmass TT
2/)]())()((|)()([|~ 2121 METppMETppPmass TTTT
)]())()((2/)))(()([(~ 2121 METppMETEEmassB TT
Rough mass of neutralino
• Many questions on mass: Not accurate; Bias? Shape? Backgrounds?
• Signal can be fitted with CB Line?• Bkg shapes are expected to be similar (CB Line +
Polynomial functions) can study all backgrounds together?
• mass2weighted can be used for bkg study or as a cross check.
![Page 14: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/14.jpg)
14
De-convolution Method
• Convolution: b
adtgftgf )()())((
dtgtfttgf
gbfafgbfgaf
fffggf
)()())((
)(
;
00
2121 linear
shift-invariant
f(mass)
(mass)gf
system: g(mass)
hgnrb )(• Mass:
Briet-Wigner
(Delta)Resolution
(Gaussian)
noise
(Argus)
transfer
rough
mass
![Page 15: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/15.jpg)
15
gfh • Rough mass in Data:
• Accurate mass in Data : nrbf
• Rough mass in signal MC:
• Accurate mass in signal MC:
gfh
rbf • Suppose we know h and f for signal MC;
• We can determine the transfer function g by deconvolution using signal MC.
• In Fourier space: FGHgfh • h, f H, F G g (signal MC)
• h, g H, G F f (Data)
![Page 16: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/16.jpg)
16
Gaussian f
(mean=mass0
rough sigma)
? =
Signal MC: GM1b~1g
RooFit
system: g
• h• Peak=196
• RMS=112
![Page 17: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/17.jpg)
17
hgfgnrb )(
• signal MC:
• Data :
hgfgrb
)()0(
)()(
)0(
)0(0 masshmassmassg
massgbmassgrb
r
massb
• h0
• Peak=175
• RMS=89
• h• Peak=196
• RMS=112)0(massb
• Peak=196.8GeV
![Page 18: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/18.jpg)
18
• g• Mean=1GeV
• RMS=89
• h• Mean=235
• Peak=196
• RMS=112
• f• Mean=196GeV
• RMS=70
hgf
)()0( 0 masshmassmassg
Signal MC:
GM1e
Gold deconvolution
algorithm
![Page 19: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/19.jpg)
19
• Convolution is largely used in: Statistics; Astronomy; Meteorology; Geophysics; Optics; Digital image; Spectroscopy; …; but not in Particle physics as I know.
• Deconvolution can be used to recover the missing information. MET, resolution, … mass, width, …
• A shadow is the convolution of the shape of the light source that is casting the shadow and the object whose shadow is being cast
• An out-of-focus photograph is the convolution of the sharp image with the shape of the iris diaphragm.
• An echo is the convolution of the original sound with a function representing the various objects that are reflecting it.
• ……
wikipedia
![Page 20: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/20.jpg)
20
• We can use mass to get signal yield, CB Line functions. Same methods as in MET for bkg studies; or bkg studies are simple.
• We can use mass-mass2weighted as a cross check of the result.
• De-convolution method is introduced, which is expected to be useful in experimental particle physics.
• Test the invariant mass and the de-convolution method with all GMSB points and all backgrounds.
• Study the QCD control samples:
• Correlation between shower shape/isolation and MET/mass need to be studied.
• Can shower shape/isolation get enough control sample? Do we need photon Pt, MET, number of jets, or jets’ pt for control sample?
Summary
Thank you!
![Page 21: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/21.jpg)
21
MT2
• hep-ph/9906349
• Left edge is known; use the right edge to get the mass.
• Enough signal events close to the right edge?
• Edge is not sharp; shape? Background?
![Page 22: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/22.jpg)
22
Edge of invariant mass
Jet+photon
2 leptons
2 leptons+1photon
• CMS Note 1997/079
• Kinematics reasons
![Page 23: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/23.jpg)
23
Accurate calculation with cross-events
• 6 constraints; 8 unknowns for one event.
• 6+10 constrains; 16 unknowns for two events. solve the equations
• Need long decay chain.
• Wrong combinations are large.
• Bias? Shape? ill equations? measure uncertainties? ...
• arXiv:0802.4290v1
![Page 24: Status of GMSB studies](https://reader035.fdocuments.in/reader035/viewer/2022062517/5681302a550346895d95b97a/html5/thumbnails/24.jpg)
24
Long-lived neutralino
• arXiv:0804.1043v1 Search for heavy, long-lived neutralinos that decay to photons at CDF II using photon timing
• arXiv:0704.0760v1 Search for heavy, long-lived particles that decay to photons at CDF II
• arXiv:0710.2647v1 Search for GMSB NLSPs at LHC
• PRD 69, 035003 (2004) Study of the gauge mediation signal with nonpointing photons at the CERN LHC
• ……