Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://zebu.uoregon.edu/~uochep/talks/talks00/brau_D3.pdf Äàòà èçìåíåíèÿ: Fri Apr 13 00:54:44 2001 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 10:33:29 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 5

Higgs Branching Ratio Measurements at the Linear Collider and Vertex Detection
J. Brau, M. Iwasaki, C. Potter, N. Sinev University of Oregon Eugene, OR 97403
Higgs Branching Ratio measurements Vertex Detector Parameter dependences Neutron Radiation Damage Studies IEEE Trans. Nuclear Science (2000)

J. Brau, LCWS 2000, October 25, 2000


Higgs Branching Ratio Measurements at the Linear Collider and Vertex Detection The physics opportunities of a future Linear Collider motivates a detector with the best possible vertex detector: Higgs branching ratios Higgs self coupling SUSY physics, eg. staus Top physics W/Z reconstruction Z pole physics .....and the event rates will be small. So we really want to optimize performance The measurement of Higgs decay modes it a particularly good benchmark physics process for the vertex detector design: Significant physics goal Rich in secondary vertexing Contains mixture of strong and weak channels
J. Brau, LCWS 2000, October 25, 2000


MSSM h0 Branching Ratios (Maximal Mixing)

HDECAY, Djouadi, Kalinowki, Spira, DESY 97-079 (1997)

J. Brau, LCWS 2000, October 25, 2000


SLD's VXD3
307,000,000 pixels 3.8 µm point resolution Excellent b/c tagging We can do even better

J. Brau, LCWS 2000, October 25, 2000


J. Brau, LCWS 2000, October 25, 2000

799,000,000 pixels standalone tracking w/ 5 barrels


Vertex Detector Parameters
Hit resolution Number of barrels Thickness of barrels (rad. lengths) Angular coverage Readout speed Material inside vertex detector (beampipe, etc.) Radiation hardness

Spectrum from B decays in ZH events
J. Brau, LCWS 2000, October 25, 2000


Radiation Hardness Tests of CCDs
Nick Sinev (http://blueox.uoregon.edu/~jimbrau/talks/IEEE-99/ieee99.pdf, to be published in IEEE Trans. Nucl. Science (2000))

Background estimates have varied from 107 n/cm2/year to 1011 n/cm2/year - 2.3 x 109 n/cm2/year (Maruyama-Berkeley2000) Expected tolerance for CCDs in the range of 109-10 Increase tolerance to neutrons can be achieved through improve understanding of issues and sensitivity engineering advances flushing techniques supplementary channels bunch compression & clock signal optimization This study investigated flushing techniques on spare VXD3 CCD @SLAC ~ 2 â 109 n/cm2 ,Troom, Pu(Be), 4 MeV @SLAC Annealing study 100° C for 35 days @Reactor (I) ~ 2 â 109 n/cm2, Troom, reactor, 1 MeV @Reactor (II) ~ 1.2 â 109 n/cm2 , T~190K, reactor , 1 MeV Total exposure ~ 5.2 â 109 n/cm2
J. Brau, LCWS 2000, October 25, 2000


Image of damaged sites

Image of damaged sites after flushing

J. Brau, LCWS 2000, October 25, 2000


Signal Loss Results from Exposures
~ 2 â 109 n/cm2 ~ 5.2 â 109 n/cm2

T = 185K, cluster sum no flushing light

4.05%

29.1%

T = 185K, cluster sum with flushing light

1.5%

18.0%



T = 178K

11.0%



Note () - flush is only partially effective in test set-up due to required delay between flush and readout (1 second) In LC detector ­ much reduced loss with flushing

J. Brau, LCWS 2000, October 25, 2000


Vertex Detector Design for the future Linear Collider
· Maximum Precision ( < 4 µm) · Minimal Layer Thickness (1.2% X0 0.4% X0 0.12% X0 0.06% X0)
SLD-VXD2 SLD-VXD3 Linear Collider stretched

· Minimal Layer 1 Radius (28 12 mm 5mm)
SLD-VXD3 LC Schumm challenge

· Polar Angle Coverage (cos ~ 0.9) · Standalone Track Finding (perfect linking) · Layer 1 Readout Between Bunch Trains

J. Brau, LCWS 2000, October 25, 2000


Event simulation
· Pandora-pythia and Pythia v5.7
­ beamstrahlung included and important

· Detector model : L2
e+ e- ZH H bb H H cc H gg H WW e+ e- WW e+ e- e+ e- qq e+ e- tt s = 500 GeV MH = 140 GeV/c2 L = 500 fb-1 Analysis with Z l+ l- evts, scaled to Z qq (OPAL, D. Strom)

Very Preliminary Results Presented in this Talk Previous studies: Hildreth, Barklow, Burke, PRD49, 3441 (1994) M. Battaglia, HU-P-264 (1999) G. Borisov, F. Richard, LAL-99-26 (1999)
J. Brau, LCWS 2000, October 25, 2000


ZVTOP
· Vertex reconstruction is based on the SLD algorithm ZVTOP ­ D. Jackson, NIM A388, 247 (1997) · Implemented in the ROOT based NLC software by T. Abe (see last talk) · Provides secondary vertex reconstruction, and ptcorrected mass

M=p

T

+

V

2

+ pT

2

J. Brau, LCWS 2000, October 25, 2000


Higgs decay tags
Z -> leptons (MZ ±10 GeV/c2) recoiling Higgs mass calculated

Higgs mass 130-150 GeV/c B tag Msec

2

-vtx

(pt-corrected) > 2.0 GeV/ c

2

c tag Msec-vtx(pt-corrected) < 2.0 GeV/ c Only 1 ZVTOP secondary vertex p(jet)/p(expected) > 0.45

2

J. Brau, LCWS 2000, October 25, 2000


p(vertex)/p(expected)
p p
Z
ZVTOP

2

p p pH = p1 + p2 = - pZ p1T = f (MH, m1, sin ) p1 = p1T / sin , (p-expected)
1

H

where sin is determined by VXD analysis by ZVTOP

J. Brau, LCWS 2000, October 25, 2000


W, tau, glue tags · W tag (l q q)
­ 3 leptons, non-Z p > 10 GeV ­ Econe(cos l <0.95) < 10 GeV ­ track mult >6

· tau tag
­ track mult 2-8 ­ anti W tag ­ max bnorm > 4

· glue-glue tag
­ analyze as two jet event ­ no sec. Vtx, no non-Z lepton w/ p>1 GeV/c, ­ not tagged as tau-tau, bb, cc, or WW
J. Brau, LCWS 2000, October 25, 2000


Efficiencies and Purities
(MH = 140 GeV/c2 , s = 500 GeV, Model L2) Eff. H bb H H cc H gg H WW
*

Signal/Backg. 5.3 1.6 0.2 0.06 3.6

0.30 0.30 0.19 0.21 0.09

Preliminary (not optimized)

J. Brau, LCWS 2000, October 25, 2000


Branching Ratio Errors
(MH = 140 GeV/c2 , s = 500 GeV, L = 500 fb-1, Model L2) H bb H H cc H gg H WW
*

0.390 ± 0.014 0.034 ± 0.005 0.024 ± 0.011 0.034 ± 0.020 0.458 ± 0.031

Preliminary (not optimized)

J. Brau, LCWS 2000, October 25, 2000


Detector Parameter Dependence Branching Ratio Errors
(MH = 140 GeV/c2 , s = 500 GeV, L = 500 fb-1) L2 H bb H H cc H gg H WW
*

2.4 cm radius* ± .017 ± .006

L2 3.0 µm res.

± .014 ± .005

± .011(46%) ± .014 (60%) ± .020(59%) ± .026 (78%) ± .031 * ± .035
(optimistic-primary vtx)

Preliminary (not optimized)
J. Brau, LCWS 2000, October 25, 2000


Conclusions

·We have reported first results of a study of the sensitivity of the Higgs branching ratio measurements to the vertex detector parameters ·Future plans ·add neural net analysis of selection parameters ·ZVTOP studies ·expand base of vertex detector variations ·add Z qq selection

J. Brau, LCWS 2000, October 25, 2000