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Study of the process of scalar top pairs production at ILC
A.Bartl (Univ. of Vienna) W.Majerotto HEPHY (Vienna) K.Moenig DESY (Zeuthen) A.N.Skachkova, N.B.Skachkov JINR (Dubna)


The Photon beams at ILC
The option of a photon collider at ILC will be achieved by using backscattered photon beams by Compton scattering of laser beams with electron ones. Unlike the situation at e+e- collider, the energy of the backscattered photon beams will vary from event to event. Circe2 program gives the energy spectra of the colliding backscattered photons & the values of photon beam luminosities.
2

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Energy spectrum from CIRCE 2
shows the degree of monochromaticity of the backscattered photons

We used as a reasonable approximation the CIRCE2 output spectra generated for E tot e+e- = 800 GeV and scaled them (by 1000/800) to the higher beam energy 2Eebeam = 1000 GeV
в 10 3500 3000 2500 2000 1500 1000 500 00 50 100 150 200 250 300 350 400 450 500 P1 , GeV
3

Mean RMS Underflow

131.8 153.8 0

Overflow 0 Integral 1.522e+07

The left peak is caused by multiple Compton scattering and beamstrahlung photons The right one at the energy fraction Y = Ei / Eebeam 0.83 (i=1,2) is due to the hard photon production
stop stop bar production

Only on a 0.3% the energy is high enough for

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized



3

collisions at ILC"


-energy correlation Y1/Y2 spectra for J=0 enhanced
(J ­ total angular momentum)
y
0.9 0.8 0.7 0.6 Mean x 0.2635 Mean y 0.2582 0.3077 RMS x RMS y 0.3055 Integral 1.522e+07 0 0 0 0 1.521539e+07 0 0 0 0

y

1

1

2

2

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
Mean x 0.3076 Mean y 0.3034 RMS x 0.3313 RMS y 0.3299 Integral 1.242e+06 0 0 0 0 1241712 0 0 0 0

Whole spectrum

0.5 0.4 0.3 0.2 0.1 0 0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

y

1
1

0 0

0.1 0.2

0.3 0.4 0.5 0.6 0.7 0.8

0.9

y

1
1
0.5625 0.5643 0.2379 0.2358 5e+04 0 0 0

spectra above stop pair production threshold

220 200 180 160 140 120 100 80 60 40 20 0

Mean x 0.6291 Mean y 0.6318 RMS x 0.1927 RMS y 0.1917 Integral 5e+04 0 0 0 0 50000 0 0 0 0

Gen

350 300 250 200 150 100 50 0

N

Mean x Mean y RMS x RMS y Integral 0 0 0 50000 0 0

NGen

y

1 0.9 0.8 2 sig 0.7 1 0.6 0.5 0.8 0.9 0.4 y 1 sig 0.6 0.7 0.3 0.40.5 0.2 0.2 0.3 0.1 0 0 0.1

y

1 0.9 0.8 2 sig 0.7 0.6 0.5 0.8 0.9 1 0.4 0.6 0.7 y 1 sig 0.3 0.4 0.5 0.2 0.2 0.3 0.1 0 0 0.1

Polarizations + - /-+ -

Polarizations + +/- -

4

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized QFTHEP A.N.Skachkova pair production polarized



collisions at ILC" ILC


W
-

~0
1

e+ e- CM energy = 1000 GeV
~
1


~ t
~+
1

~ t

b

1

STOP pair production cross sections

W+
~0
1

b

1

qj

= 2.03 fb = 3.46 fb
W
-

"+ -" & "- +" "+ +" & "- -"

qi

4-6 factor difference
TOP pair production cross sections


b

t



= 13.17 fb = 15.57 fb

"+ -" & "- +" "+ +" & "- -"

t
b W
+

qj qi

PYTHIA 6.4 + cross section distribution formula taken from S.Berge et al. hep-ph/0008081
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QFTHEP '2010 A.N.Skachkova. "Stop pair production in polarized collisions at ILC" QUARKS`2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC" QUARKS'2010


The subsequent decay channels have been considered:

STOP STOP b 1+ b t t b W+ b

bar bar

1 - b b

bar bar

qi qj qi qj

bar bar

- 1 є 1 є Ї


W- b b

The only difference of STOP / TOP production is the presence of the two non-detectable neutralinos in the case of stop pair production. Both the signal and background events have the same experimental signature ( b & bbar - jets, 2 jets from W qi qj decay and Ї ). The quarks hadronize into jets. Jets are determined by use of PYCLUS jetfinder based on "Durham" cluster distance measure algorithm.

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QFTHEP `2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC" collisions ILC


In order to simulate the STOP pair production, we assumed the following scenario for the MSSM model parameters: M ~Q = M ~t L = 270 GeV (left squark mass) M~U = M ~t R = 270 GeV (right squark mass) At = -500 GeV (top and bottom trilinear coupling) = - 370 GeV Corresponds to tan = 5 M1 = 80 GeV Mstop1 = 167.9 GeV, M 1є = 80.9 GeV M2 = 160 GeV
Mstop2 = 409.9 GeV, M
1+

= 159.2 GeV

Our aim is: To find out physical variables (Energy, PT, angle and invariant mass distributions) most suitable for signal (stop) / background (top) separation To estimate the corresponding values of cuts on these variables
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QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


STOP Energy distributions
The shapes of these spectra follow backscattered -energy distributions

Mean

311

Nev

RMS 53.88 0 100 Underflow Overflow 0 80 Integral 3339
60 40 20 00 50 100 150 200 250 300 350 400 450 500 ~ E t 1, GeV

Nev

180 160 140 120 100 80 60 40 20 00

Mean RMS Underflow Overflow Integral

273.7 73.42 0 0 5173

50 100 150 200 250 300 350 400 450 500 ~ E t 1 , GeV

Polarization : +- / -+

Polarization : ++/ -8

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


STOP PT distributions
100 80 60 40 20 00

Mean 214.5 RMS 66.32 Underflow 0 Overflow 0 Integral 3339

Nev

Nev

180 160 140 120 100 80 60 40 20

Mean RMS Underflow Overflow Integral

111.3 72.58 0 0 5173

50 100 150 200 250 300 350 400 450 500 ~ PT t 1, GeV

0 0

50 100 150 200 250 300 350 400 450 500 ~ PT t 1 , GeV

Polarization : +- / -+

Polarization : ++/ --

The PT-spectrum for "++/--" polarization is much softer then for "+-/-+" polarization
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QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


STOP angle distributions
Nev Nev
60 50 40 30 20 10 00 0.5 1 1.5 2 2.5 3 b, radians

Mean 1.574 RMS 0.6465 Underflow 0 Overflow 0 Integral 3345

80 70 60 50 40 30 20 10 0 0.5

Mean 1.574 RMS 0.9694 Underflow 0 Overflow 0 Integral 5173

1

1.5

2

2.5 3 ~ t 1, radians

Polarization : +- / -+

Polarization : ++/ -10

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Minv (stop+stopbar) = Minv () = (P1 + P2)2 distributions
The shapes of these spectra also follow backscattered -energy distributions
Mean RMS Underflow Overflow Integral 597 108 0 0 1669

50 40 30

120 100 80 60

Mean RMS Underflow Overflow Integral

505.8 144.6 0 0 2587

Nev

20 10 0 0 100 200 300 400 500 600 700 800 900 1000 ~ ~ Minv ( t 1 + t 1), GeV

Nev
40 20 0 0

100 200 300 400 500 600 700 800 900 1000 ~~ Minv t 1+ t 1, GeV

Polarization : +- / -+

Polarization : ++/ -11

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


E- spectra of quarks from W
Nev
180 160 140

STOP

120 100 80 60 40 20 00

Mean 65.44 RMS 40.36 Underflow 0 Overflow 0 Integral 3319

350 300 250 200 150 100 50

Mean 57.57 RMS 36.44 Underflow 0 Overflow 0 Integral 5098

Nev

50 100 150 200 250 300 350 400 450 500 EW-quark, GeV

0 0

50 100 150 200 250 300 350 400 450 500 EW-quark, GeV

1000 800

Mean 85.8 RMS 55.12 Underflow 0 Overflow 0 Integral 2.293e+04

Mean

97.98 65.09 0

Nev

Nev

RMS Underflow

1000 800 600 400 200 0 0

Overflow 0 Integral 2.72e+04

TOP

600 400 200 00

50 100 150 200 250 300 350 400 450 500 EW-quark, GeV

50 100 150 200 250 300 350 400 450 500 EW-quark, GeV

Polarization : +- / -+

Polarization : ++/ --

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QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


PT- spectra of quarks from W
STOP
240 220 200 180 160 140 120 100 80 60 40 20 0 0

Mean 52.89 RMS 36.04 Underflow 0 Overflow 0 Integral 3319

500 400 300 200 100 00

Mean RMS Underflow Overflow Integral

38.37 24.8 0 0 5098

Nev

Nev

50 100 150 200 250 300 350 400 450 500 PT W-quark, GeV

50 100 150 200 250 300 350 400 450 500 PT W-quuark, GeV
Mean RMS 68.52 50.02

Nev

Nev

1600 1400

TOP

1200 1000 800 600 400 200 0 0

Mean 60.22 RMS 41.21 Underflow 0 Overflow 0 Integral 2.293e+04

1600 1400 1200 1000 800 600 400 200

Underflow 0 Overflow 0 Integral 2.72e+04

50 100 150 200 250 300 350 400 450 500 PT W-quark, GeV

0 0

50 100 150 200 250 300 350 400 450 500 PT W-quark, GeV

Polarization : +- / -+

Polarization : ++/ --

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QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


E- spectra of jets from W
300 250

STOP

200 150 100 50 0 0

Mean 46.24 RMS 36.85 Underflow 0 Overflow 0 Integral 3339

600 500 400 300 200 100

Mean 40.12 RMS 35.12 Underflow 0 Overflow 0 Integral 5173

Nev

Nev

50 100 150 200 250 300 350 400 450 500 Ejet , GeV
W*

0 0

50 100 150 200 250 300 350 400 450 500 Ejet , GeV
W*

1000 800

Mean 86.38 RMS 55.56 Underflow 0 Overflow 0 Integral 2.323e+04

Nev

1000 800 600 400 200 0 0

Nev

Mean RMS

100.7 66.15

TOP

Underflow 0 Overflow 0 Integral 2.757e+04

600 400 200 0 0

50 100 150 200 250 300 350 400 450 500 Ejet , GeV
W

50 100 150 200 250 300 350 400 450 500 Ejet , GeV
W

Polarization : +- / -+

Polarization : ++/ --

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QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


PT- spectra of jets from W
Mean 35.74 31.42 0 0 3339

Mean

26.15 24.1 0 0 5173

Nev

RMS Underflow Overflow Integral

Nev

450 400 350

800 700 600 500 400 300 200 100

STOP

300 250 200 150 100 50 0 0

RMS Underflow Overflow Integral

50 100 150 200 250 300 350 400 450 500 PT jet , GeV
W*

00

50 100 150 200 250 300 350 400 450 500 PT jet , GeV
W*

Nev

Nev

1600 1400 1200 1000

Mean 59.04 RMS 41.53 Underflow 0 Overflow 0 Integral2.323e+04

Mean
1600 1400 1200 1000 800 600 400 200

68.89 51.05

RMS

Underflow 0 Overflow 0 Integral 2.757e+04

TOP

800 600 400 200 0 0 50 100 150 200 250 300 350 400 450 500 PT jet , GeV
W

0 0

50 100 150 200 250 300 350 400 450 500 PT jet , GeV
W

Polarization : +- / -+

Polarization : ++/ -15

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


W mass reconstruction as Minv of 2 Wjets
300 250

60 50 40

STOP

200 150

30
100

20
50

10
0 0 20 40 60 80 100 120 140 160 180 200 MW* = Minv (q +q ), GeV
1 2

0 0

20

40

60

80

100 120 140 160 180 200 MW* = Minv (Jets ), GeV
W*

5000 4000

Mean 80.52 RMS 9.297 Underflow 0 Overflow 32.5 Integral 1.158e+04

1600 1400 1200 1000 800

Mean 83.18 RMS 23.47 Underflow 0 Overflow 214 Integral 1.14e+04

TOP

3000 2000 1000 0 0

600 400 200

20

40

60

80 100 120 140 160 180 200 MW = Minv (q +q ), GeV
1 2

0 0

20

40

60

80 100 120 140 160 180 200 MW = Minv (Jets ), GeV
W

Partonic level

Level of jets
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QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"

Clear seen visible virtual nature of W boson

Mean 62.38 RMS 18.2 Underflow 0 Overflow 0.609 Integral 1669

Mean 46.68 RMS 26.6 Underflow 0 Overflow 3.73 Integral 1666

Nev

Nev

Nev

Nev


E- spectra of b-quarks
200 180 160 140 120 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 Eb, GeV

Mean 14.53 RMS 6.15 Underflow 0 Overflow 0.3045 Integral 3345

450 400 350 300 250 200 150 100 50 00 10 20 30 40 50 60

STOP

Mean 12.89 RMS 5.853 Underflow 0 Overflow 0.388 Integral 5180

Nev

Nev

70

80

90 100 Eb , GeV

800 700 600

Mean 113.2 RMS 59.23 Underflow 0 Overflow 0 Integral 2.326e+04

800 700 600 500 400 300 200 100

Mean 129.7 RMS 70.61 Underflow 0 Overflow 0 Integral 2.762e+04

Nev

TOP

500 400 300 200 100 00 50 100 150 200 250 300 350 400 450 500 Eb, GeV

Nev

00

50 100 150 200 250 300 350 400 450 500 Eb, GeV

Polarization : +- / -+

Polarization : ++/ -17

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


PT- spectra of b-quarks
200 180 160 140

Mean 10.95 RMS 6.148 Underflow 0 Overflow 0.1142 Integral 3345

600 500 400 300 200 100

Mean 7.404 RMS 4.406 Underflow 0 Overflow 0.2587 Integral 5181

Nev

STOP

120 100 80 60 40 20 00
10 20 30 40 50 60 70 80 90 100

Nev

PT b , GeV

00

10

20

30

40

50

60

70

80 90 100 PT b , GeV

1200 1000

TOP

Mean 78.72 RMS 45.38 Underflow 0 Overflow 0 Integral 2.326e+04

Mean

89.77 56.05

Nev

Nev

1200 1000 800 600 400 200

RMS

Underflow 0 Overflow 0 Integral 2.762e+04

800 600 400 200 0 0 50 100 150 200 250 300 350 400 450 500 PT b, GeV

0 0

50 100 150 200 250 300 350 400 450 500 PT b, GeV

Polarization : +- / -+

Polarization : ++/ --

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QFTHEP '2011A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


E- spectra of b-jets
(B-jet is determined as a jet that includes b-meson)
100 80 60 40 20 0 0

STOP

Mean RMS Underflow Overflow Integral

30.67 24.56 0 374.2 2965

180 160 140 120 100 80 60 40 20 0 0

Mean RMS Underflow Overflow Integral

28.57 23.51 0 369.2 4804

Nev

10

20

30

40

50

60

70

80 90 100 Eb-jet, GeV

Nev

10

20

30

40

50

60

70

80 90 100 Eb-jet , GeV

800 700

TOP

600 500 400 300 200 100 0 0

Mean 109.9 RMS 58.76 Underflow 0 Overflow 0 Integral 2.323e+04

800 700 600 500 400 300 200 100

Mean 127.5 RMS 69.98 Underflow 0 Overflow 0 Integral 2.757e+04

Nev

Nev

50 100 150 200 250 300 350 400 450 500 Eb-jet, GeV

00

50 100 150 200 250 300 350 400 450 500 Eb-jet, GeV

Polarization : +- / -+

Polarization : ++/ --

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QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


PT- spectra of b-jets
120 100

Mean RMS Underflow Overflow Integral

26.13 24.17 0 199.4 3140

300 250 200 150 100 50

Mean RMS Underflow Overflow Integral

19.95 19.58 0 83.87 5089

Nev

STOP

80 60 40 20 0 10 20 30 40 50 60 70 80 90 100 PT b-jet, GeV

Nev

00

10

20

30

40

50

60

70

80 90 100 PT b-jet, GeV

1200 1000

TOP

Mean 74.94 RMS 44.7 Underflow 0 Overflow 0 Integral 2.323e+04

1200 1000 800 600 400 200

Mean 86.71 RMS 55.38 Underflow 0 Overflow 0 Integral 2.757e+04

Nev

800 600 400 200 0 0 50 100 150 200 250 300 350 400 450 500 PT b-jet, GeV

Nev

0 0

50 100 150 200 250 300 350 400 450 500 PT b-jet, GeV

Polarization : +- / -+

Polarization : ++/ -20

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


of b-quarks for stop production
Mean 1.574 RMS 0.6465 Underflow 0 Overflow 0 Integral 3345

Nev

50 40 30 20 10

Nev

60

70 60 50 40 30 20 10 Mean 1.57 RMS 0.8338 Underflow 0 Overflow 0 Integral 5181

00

0.5

1

1.5

2

2.5 3 b, radians

00

0.5

1

1.5

2

2.5

b , degrees

3

Polarization : +- / -+

Polarization : ++/ --

21

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Cos (b, bbar) spectra for Stop pairs production
Mean -0.54
70 60 50 40 30 20 10 0 -1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 1 cos(b, b)

RMS 0.4239 Underflow 0 Overflow 0 Integral 1669

80 70 60 50 40 30 20 10 -1 -0.8 -0.6 -0.4 -0.2 -0

Mean -0.3348 RMS 0.5465 Underflow 0 Overflow 0 Integral 2587

Nev

Nev

0.2 0.4 0.6 0.8 1 cos(b, b)

Polarization : +- / -+

Polarization : ++ / --

Most of b- and b bar ­ jets move approximately in the opposite directions, but some are in the same hemisphere
22

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


distributions in the signal events
40 35

E

30 25 20 15 10 5 0 0 20 40 60

Mean RMS Underflow Overflow Integral

58.77 40.19 0 5.899 1652

Nev

1400 1200 1000 800 600 400 200

Nev

Mean RMS

0.8486 1.239

Underflow 0 Overflow 46.82 Integral 6794

80 100 120 140 160 180 200 Esig_mu, GeV

00

1

2

3

4

5

6

7

8 9 10 Edec_mu, GeV

100

PT

80 60 40 20 00

Mean RMS Underflow Overflow Integral

34.89 25.05 0 0.776 2546

Mean

0.5866

Nev

Nev

1400 1200 1000 800 600 400 200

RMS 0.9665 Underflow 0 Overflow 18.69 Integral 6822

20

40

60

80 100 120 140 160 180 200 PT sig_mu, GeV

0 0

1

2

3

4

5

6

7 8 9 10 PT dec_mu, GeV

Signal 's

Fake 's
23

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Missing energy ( , ~1є , beam pipe) distributions
70 60 50

Mean 430.1 RMS 97.14 Underflow 0 Overflow 0 Integral 1669

100 80 60 40 20

Mean RMS Underflow Overflow Integral

394.6 116 0 0 2587

Nev

STOP

40 30 20 10 0 0 100 200 300 400 500 600 700 800 900 1000 Emiss_tot, GeV

Nev

0 0

100 200 300 400 500 600 700 800 900 1000 Emiss_tot, GeV

800 700 600

Mean 117.3 RMS 65.53 Underflow 0 Overflow 0 Integral 1.162e+04

800 700 600 500 400 300 200 100

Mean 133.3 RMS 76.87 Underflow 0 Overflow 0 Integral 1.378e+04

Nev

TOP

500 400 300 200 100 0 0 100 200 300 400 500 600 700 800 900 1000 Emiss_tot, GeV

Nev

0 0

100 200 300 400 500 600 700 800 900 1000 Emiss_tot, GeV

Polarization : +- / -+

Polarization : ++ / --

24

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Total scalar ni=1 |PTi| variable
A cut PT
skalsum
Nev

< 180 GeV would lead to a good Signal / Background separation
Mean 140.2 RMS 48.41 Underflow 0 Overflow 0 Integral 1669
400 350 300 250 200 150 100 50

140 120

STOP

Mean RMS Underflow Overflow Integral

100.8 44.47 0 0 2587

100 80 60 40 20 0 0 100 200 300 400 500 600 700 800 900 1000 PT scalsum, GeV

Nev

0 0

100 200 300 400 500 600 700 800 900 1000 PT scalsum , GeV

500 400 300 200 100 00

Mean 328.1 RMS 98.71 Underflow 0 Overflow 0 Integral 1.162e+04

500 400 300 200 100 00

Mean 379.6 RMS 129.7 Underflow 0 Overflow 0 Integral 1.378e+04

Nev

TOP

100 200 300 400 500 600 700 800 900 1000 PT scalsum, GeV

Nev

100 200 300 400 500 600 700 800 900 1000 PT scalsum, GeV

Polarization : +- / -+

Polarization : ++/ - -

25

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Missing mass
Mmissing = (s(Njet
100 80

Enjet+E))2(Njet n=1
Nev
160 140 120 100 80

Pnjet+P))2 n=1
Good for Signal / Background separation !
26

Mean RMS Underflow Overflow Integral

756.2 71.25 0 0 1669

Mean 787.1 RMS 79.51 Underflow 0 Overflow 0 Integral 2587

STOP

Nev

60 40 20 0 0

60 40 20 100 200 300 400 500 600 700 800 900 1000 Mmissing, GeV 00 100 200 300 400 500 600 700 800 900 1000 Mmissing, GeV

400 350 300

Mean 493.7 RMS 108.3 Underflow 0 Overflow 0 Integral 1.162e+04

400 350 300 250 200 150 100 50

Mean 423.6 RMS 129 Underflow 0 Overflow 0 Integral 1.378e+04

TOP

250 200 150 100 50 00 100 200 300 400 500 600 700 800 900 1000 Mmissing, GeV

0 0

100 200 300 400 500 600 700 800 900 1000 Mmissing, GeV

Polarization : +- / -+

Polarization : ++/ --

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"

Mmissing > 650 GeV

Nev

Nev


Invariant mass of 4jets +
Good for Signal / Background separation with a cut < 230 GeV!
90 80 70 60

Mean RMS Underflow Overflow Integral

206.7 73.9 0 0 1669

STOP

50 40 30 20 10 0 0 100 200 300 400 500 600 700 800 900 1000 Minv (All jets, ), GeV

240 220 200 180 160 140 120 100 80 60 40 20 0 0

Mean 174.6 RMS 77.87 Underflow 0 Overflow 0 Integral 2587

Nev

Nev

100 200 300 400 500 600 700 800 900 1000 Minv (All jets, ), GeV

400 350 300

Mean 427.5 RMS 115.5 Underflow 0 Overflow 0 Integral 1.162e+04

300 250 200 150 100 50

Mean 514.9 RMS 147.3 Underflow 0 Overflow 0 Integral 1.378e+04

Nev

TOP

250 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 1000 Minv (All jets, ), GeV

Nev

0 0

100 200 300 400 500 600 700 800 900 1000 Minv (All jets, ), GeV

Polarization : +- / -+

Polarization : ++ / --

27

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Invariant mass of 4 jets
Minv(All jets)=(i=1,2,3,4iPijet)2
Perfect for Signal / Background separation with cut M f
240 220 200 180 160 140 120 100 80 60 40 20 0 0

inv

< 180 GeV!
112.1 50.7 0 0 2587

STOP

Mean 127.2 RMS 47.38 Underflow 0 Overflow 0 Integral 1669

500 400 300 200 100 0 0

Mean RMS Underflow Overflow Integral

Nev

100 200 300 400 500 600 700 800 900 1000 Minv (All jets), GeV

Nev

100 200 300 400 500 600 700 800 900 1000 Minv (All jets), GeV

500 400

TOP

Mean 335.5 RMS 103.9 Underflow 0 Overflow 0 Integral 1.162e+04

400 350 300 250 200

Mean 401.2 RMS 135 Underflow 0 Overflow 0 Integral 1.378e+04

Nev

300 200 100 0 0

Nev

150 100 50 100 200 300 400 500 600 700 800 900 1000 Minv (All jets), GeV 0 0 100 200 300 400 500 600 700 800 900 1000 Minv (All jets), GeV

Polarization : +- / -+

Polarization : ++ / --

28

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Detected (visible) energy distributions
Perfect for Signal / Background separation with a cut E
140 120 100

vis_tot

< 250 GeV !
Mean 152.6 RMS 61.46 Underflow 0 Overflow 0 Integral 2587

Mean RMS Underflow Overflow Integral

176.3 53.54 0 0 1669

Nev

STOP

80 60

40 20 0 0 100 200 300 400 500 600 700 800 900 1000 Evis_tot, GeV 50 0 0

Nev

250 200 150 100

100 200 300 400 500 600 700 800 900 1000 Evis_tot, GeV

Nev

400

TOP

300 200 200 150 100 100 50 0 0 100 200 300 400 500 600 700 800 900 1000 Evis_tot, GeV 0 0 100 200 300 400 500 600 700 800 900 1000 Evis_tot, GeV

Polarization : +- / -+

Nev

500

Mean 468 RMS 101.7 Underflow 0 Overflow 0 Integral 1.162e+04

350 300 250

Mean 542.6 RMS 130.1 Underflow 0 Overflow 0 Integral 1.378e+04

Polarization : ++ / --

29

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Used cuts for S/B separation
Polarization : +- / -+ Polarization : ++ / -Stop cut efficiency = 0.80 Top cut efficiency = 0.94

1. )

The events with clear recognized 2 B-jets (according to PYTHIA)
Stop cut efficiency = 0.88 Top cut efficiency = 0.94

But, in the experiment only 50% efficiency of the B-jets and B bar-jets separation and the 80% of the corresponding purity is expected

2. ) Invariant mass of all jets M

together with the cut above Stop cut efficiency = 0.89 Stop cut efficiency = 0.92 Top cut efficiency = 0.012 Top cut efficiency = 0.008

inv(All

jets) < 180 GeV

3. ) Visible energy < 250 GeV
together with the cut above Stop cut efficiency = 0.98 Stop cut efficiency = 0.98 Top cut efficiency = 0.176 Top cut efficiency = 0.175
30

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Final results of S/B separation
Polarization : +- / -+ Polarization : ++ / --

Achieved S/B ratio

59
23 %

120
With a loss of signal events 28 %

The rest of Background events per year is only

24

19

while the estimated rate of Signal events per year

1484

2375
31

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Invariant mass of Bjet & 2jetsW
Can also be used for Signal / Background separation with a cut < 120 GeV!
Mean 86.68

Nev

Nev

250 200 150 100 50

RMS Underflow Overflow Integral

37.9 0 0 1669

350 300 250 200 150 100 50

Mean RMS Underflow Overflow Integral

70.16 23.18 0 0 2375

STOP

0 0

50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W*

0 0

50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W*

Nev

Nev

3000 2500 2000

Mean 176.5 RMS 41.31 Underflow 0 Overflow 5.91 Integral 1.161e+04

Mean
3000 2500 2000 1500 1000 500

187.5 56.66

RMS

Underflow 0 Overflow 52.09 Integral 1.373e+04

TOP

1500 1000 500 00 50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W

0 0

50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W

Polarization : +- / -+

Polarization : ++ / --

32

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


The most important variable invariant mass of Bjet & 2jetsW
M
inv

( b , 2 quark

In the case of TOP pair production it gives The mass reconstruction of the top-quark M M
inv Top

W

)

Entries Mean RMS

1000000 171.4 10.13 0 0 3.579e+04

25000 20000 15000 10000 5000 0 0

Underflow Overflow Integral

50

100 150 200 250 300 350 400 450 500 GeV

( Bjet & 2jetsW ) = M

Top

Nev

(175 GeV) :

3000 2500 2000 1500 1000 500 00

Mean 176.5 RMS 41.31 Underflow 0 Overflow 5.91 Integral 1.161e+04

50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W

33

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Stop invariant mass
The reconstruction of the STOP invariant mass M
STOP
M
inv

( b , 2 quark

W*

, chi

0 1

)

Entries Mean RMS Underflow Overflow Integral

38049 167.5 5.496 0 0 1806

1800 1600 1400 1200 1000 800

(167.9 GeV):

M

inv

(STOP) =
inv

600 400 200 00 50 100 150 200 250 300 350 400 450 500 GeV

M 1є + M

(bjet , 2jetsW) =
2

M

inv

(b

jet

, JETS

W*

, chi )
1

0

Entries Mean

38049 167.7 17.65 0 0 1806

600 500

RMS Underflow Overflow Integral

= M 1є + (Pbjet + Pjet1 W +Pjet2W)
But 1є - is not detectable particle

400 300 200 100 0 0 50

100 150 200 250 300 350 400 450 500 GeV

34

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Invariant mass of Bjet & 2jetsW
For the case of STOP pair production gives
Mean 86.68 37.9 0 0 1669

Nev

250 200 150 100 50 0 0

RMS Underflow Overflow Integral

M

inv

(Bjet , 2jetsW) = M

inv

(STOP) - M 1є

50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W*

Nev

Right edge of Minv (Bjet , 2jetW) 87 GeV M 1є 80 GeV Mstop = M 1є + M = 167 GeV
in v(Bjet , 2jetW) =

350 300 250 200 150 100 50 0 0

Mean RMS Underflow Overflow Integral

70.16 23.18 0 0 2375

50 100 150 200 250 300 350 400 450 500 Minv (b-jet, Jets ), GeV
W*

35

QUARKS'2010 A.N.Skachkova. "Stop pair production in polarized collisions at ILC" QFTHEP '2011


The test of the other Scalar top mass
M

M M M

stop 1є 1+

= = =

200.1 GeV 80.9 GeV 159.6 GeV

inv

(b

jet

, JETS

W*

)

Entries Mean RMS Underflow Overflow Integral

19377 92.91 20.13 0 0 509.4

50 40 30 20 10 0 0

50 100 150 200 250 300 350 400 450 500 GeV

Right edge of the peak of M

inv

(bjet , 2jetW) 120 GeV

M 1є 80 GeV Mstop = M 1є+ M є
inv(bjet

Polarization : +- / -+ Events/year : 347

++/-1379
36

, 2jetW) = 200 GeV

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Conclusion
The main results:
1. New code for cross section of STOP pairs production that allows to take into account the polarizations of colliding photons is implemented into PYTHIA 6. An account of the energy spectrum of colliding photons is done by use of CIRCE 2. 2. It is shown also that the invariant mass of the final jets and the visible energy variables turns out to be most efficient for signal / background separation. 3. A possibility of a good MSTOP reconstruction from right-hand edge point of 3 jets ( Bjet + 2 jetsW ) is demonstrated. So, finally, it is shown that in a region of small values of stop mass ~ 167 GeV the channel

STOP STOP b 1+ b 1- b b q q' - 1є 1є is very promising for the STOP-quark search!
37

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Publications
"Pair production of scalar top quarks in polarized photon-photon collisions at ILC. " Authors: A.Bartl, W.Majerotto, K.MЖnig, A.N.Skachkova, N.B.Skachkov
arXiv: 0804.1700v2, ILC-NOTE-2007-036

"Scalar top quarks production in polarized photonphoton collisions at ILC"
Authors: A.Bartl, W.Majerotto, K.Moenig, A.N.Skachkova, N.B.Skachkov Phys.Part.Nucl.Lett. V.9, N1(171), P.53-76, 2012

38

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


The case of e+e- collisions

-

W



-

~0
1

e+ e- CM energy = 500 GeV
~
1

e+
~ t
~+
1

~ t

b

1

e1

STOP pair production cross section

W+
~0 1

qj
qi

= 2.37 fb


b

W

-

b

TOP pair production cross section

e+

t

t
b
W+

eq
qi

= 35.9 fb

j

Simulation is done by use of PYTHIA 6.4 + CIRCE 1
QFTHEP '2011

39

A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Cross section dependence on Ebeam
(without any cuts) 2Ebeam[GeV] stop [fb]

Nstop 233 1347 2378 1809 1265

top [fb] 13.76 38.79 35.94 17.36 11.66

Ntop 13750 38740 35950 17359 11656
40

350 400 500 800 1000

0.23 1.34 2.37 1.89 1.42

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


e+, e- beam energy spectrum from CIRCE 1
в10 120 100 80 60 40 20 00 50 100 150 200 250 300 350 400 450 500
3

P1

e+

h7 Entries 250000 Mean 247.1 RMS 7.25 Underflow 0 Overflow 0 Integral 2.5e+05

Electron e- (positron e+) beam energy with account of beamstrahlung
Y2 / Y1
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3
h16 Entries 250000 Mean x 0.9756 Mean y 0.9758 RMS x 0.03826 RMS y 0.03811 Integral 5.507e+04 0 62799 70115 0 55072 62014 0 0 0

Correlation between e+ and e- beam spectra Yi = E i/E ibeam (i = e+,e- )

0.2 0.1 0 0

0.1 0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

The peak luminosity is supposed to be 2*1034cm-2s-1. The total luminosity required is 1000 fb-1 during the first phase of operation at 2Eebeam = See = 500 GeV.

41

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Main Scalar top quark distributions
Minv 1600
1400 RMS 1200 1000 800 600 400 200 00 100 200 300 400 500 600 700 800 900 1000 GeV Underflow Overflow Integral 0 0 2374 21.04

(STOP + STOP)

Entries Mean

50000 490.8 1600 1400

E

ST

Entries Mean RMS

50000 245.6 10.09 0 0 2374

1200

Underflow
1000

Overflow
800

Integral
600 400 200 0 0

50 100 150 200 250 300 350 400 450 500 GeV

450 400 350 300 250 200 150 100 50 0 0

PT

ST

Entries Mean RMS Underflow Overflow Integral

50000 158.2 28.71 0 0 2373

60 50 40 30 20 10 0 0

THETA

ST

Entries Mean

50000 1.569 0.5006 RMS 0 Underflow 0 Overflow Integral 2373

50 100 150 200 250 300 350 400 450 500 GeV

0.5

1

1.5

2

2.5

3 radians

42

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Missing energy ( , ~1є , beam pipe) and detected (visible) energy distributions
Good for Signal / Background separation with cut E Entries 50000 E cal_tot ! E miss_tot Mean 342.5
200 180 160 140 120

cal_tot

< 220 GeV
50000 134.5 27.12 0 0 2373

Entries Mean RMS Underflow Overflow Integral

450 400 350 300 250 200 150 100 50

RMS Underflow Overflow Integral

54.88 0 0 2373

STOP

100 80 60 40 20 0 0

100 200 300 400 500 600 700 800 900 1000 GeV

0 0

100 200 300 400 500 600 700 800 900 1000 GeV

Emiss_tot
2500 2000 1500

Entries Mean RMS Underflow Overflow Integral

1000000 105.5 48.28 0 0 3.592e+04

Ecal_tot
2500 2000 1500 1000 500

Entries Mean RMS Underflow Overflow Integral

1000000 394.5 48.28 0 0 3.592e+04

TOP

1000 500 0 0

100 200 300 400

500 600 700 800 900 1000 GeV

0 0

100 200 300 400 500 600 700 800 900 1000 GeV

Missing energy

Detected energy
43

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Total scalar PT and Invariant mass of 4jets +
Good for Signal / Background separation with the cuts PT
350 300

skalsum

< 150 GeV
Entries Mean RMS Underflow Overflow Integral 50000 109.9 26.92 0 0 2373

and

M inv ( 4 jets + ) < 200 GeV !
M
200 180 160 140 120 100 80 60 40

PT skalsum

inv

( All jets , mu )

Entries Mean RMS Underflow Overflow Integral

50000 169.5 46.6 0 0 2373

STOP

250 200 150 100 50 00

20

100 200 300 400 500 600 700 800 900 1000 GeV

0 0

100 200 300 400 500 600 700 800 900 1000 GeV

2200 2000

PT skalsum

Entries Mean RMS Underflow Overflow Integral

1000000 306.5 59.46 0 0 3.593e+04

2500 inv

M

( All jets , mu )

Entries Mean RMS

1000000 387.8 61.78 0

TOP

1800 1600 1400 1200 1000 800 600 400 200 00

2000

Underflow

1500

0 Overflow Integral 3.592e+04

1000

500

100 200 300 400 500 600 700 800 900 1000 GeV

0 0

100 200 300 400 500 600 700 800 900 1000 GeV

Scalar PT

M

inv

( 4 jets + )

44

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Invariant mass of 4 jets and Mmissing variable
PERFECT for Signal / Background separation cut M
M
450 400 350 300

inv

( 4 jets ) < 160 GeV
Entries Mean RMS Underflow Overflow Integral 50000 107.9 29.02 0 0 2373

and
120 100 80 60 40 20

M

missing
missing

> 250 GeV
Entries Mean RMS Underflow Overflow Integral 50000 304.4 45.89 0 0 2373

inv

All jets

M

STOP

250 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 1000 GeV

0 0

50

100 150 200 250 300 350 400 450 500 GeV

M
1800 1600 1400

inv

( All jets )

Entries Mean RMS Underflow Overflow Integral

1000000 307.4 64.92 0 0 3.593e+04

M
2000 1800 1600 1400 1200 1000 800 600 400 200 0 0

missing

Entries Mean RMS Underflow Overflow Integral

1000000 60.48 49.1 0 0 3.593e+04

TOP

1200 1000 800 600 400 200 0 0 100 200 300 400

500 600 700 800 900 1000 GeV

50

100 150 200 250 300 350 400 450 500 GeV

M

inv

( 4 jets )

Mmissing

45

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Used cuts for S/B separation
1. ) The events with clear recognized 2 B-jets (according to PYTHIA) (B-jet is determined as a jet that includes b-meson) Stop cut efficiency = 0.84 Top cut efficiency = 0.94

But, in the experiment only 50% efficiency of the B-jets and B bar-jets separation and the 80% of the corresponding purity is expected 2. ) Invariant mass of 4 jets (bjet, together Stop cut efficiency = 0.78 bbarjet, with the 2jetsW) M inv (All jets) < 160 GeV cut above Top cut efficiency = 0.001

3. ) Invariant Missing mass Mmissing > 250 GeV together with the cuts above Stop cut efficiency = 0.76 Top cut efficiency = 3.3*10-4

Achieved S/B ratio = 143 The rest is only 13 background events per year, while for the 46 Signal events ­ 1086/year (for the integrated Luminosity L=1000 fb-1/year)


Cross section dependence on Ebeam
(with the cuts above)

2Ebeam[GeV] stop [fb]

Nstop 8 521 1806 995 410

top [fb] 0 2.32 * 10-4 2.26 * 10-2 1.08 * 10-2 6.26 * 10-3

Ntop 0 0.2 12.6 10 6
47

350 400 500 800 1000

0.0089 0.52 1.80 0.99 0.41

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Invariant mass of bjet & 2jetsW
Can also be used for Signal / Background separation cut M
M
350 300 250
inv

inv

(bjet, 2jetsw) < 100 GeV!

(b

jet

, JETS

W*

)

Entries Mean RMS Underflow Overflow

50000 79.31 26.63 0 0 2373

STOP

200 150 100 50 00 50

Integral

100 150 200 250 300 350 400 450 500 GeV

M

9000 8000 7000

inv

(b

jet

, JETS

W

)

Entries Mean RMS Underflow Overflow Integral

1000000 179.2 40.85 0 0 3.595e+04

TOP

6000 5000 4000 3000 2000 1000 00

50 100 150 200 250 300 350 400 450 500 GeV

Minv (b-jet, 2jetsW)

48

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


The most important variable invariant mass of bjet & 2jetsW
M
inv

( b , 2 quark

W

)

Entries Mean RMS

1000000 171.4 10.13 0 0 3.579e+04

In the case of TOP pair production it gives The mass reconstruction of the top-quark M M
inv Top

25000 20000 15000 10000 5000 0 0

Underflow Overflow Integral

50

100 150 200 250 300 350 400 450 500 GeV

(175 GeV) :
Top

M

9000 8000 7000 6000

inv

(b

jet

, JETS

W

)

Entries Mean RMS Underflow Overflow Integral

1000000 179.2 40.85 0 0 3.595e+04

( Bjet & 2jetsW ) = M

5000 4000 3000 2000 1000 00

50 100 150 200 250 300 350 400 450 500 GeV

49

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Stop invariant mass
The reconstruction of the STOP invariant mass M
STOP
M
inv

( b , 2 quark

W*

, chi

0 1

)

Entries Mean RMS Underflow Overflow Integral

38049 167.5 5.496 0 0 1806

1800 1600 1400 1200 1000 800

(167.9 GeV):

M

inv

(STOP) =
inv

600 400 200 00 50 100 150 200 250 300 350 400 450 500 GeV

M 1є + M

(bjet , 2jetsW) =

M

inv

(b

jet

, JETS

W*

, chi )
1

0

Entries Mean

38049 167.7 17.65 0 0 1806

600 500 400 300 200

RMS Underflow Overflow Integral

= M 1є + (Pbjet + Pjet1 W +Pjet2W)
But 1є - is not detectable particle

100 0 0 50 100 150 200 250 300 350 400 450 500 GeV

50

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Invariant mass of Bjet & 2jetsW gives
For the case of STOP pair production gives
M
500 400
inv

( b , 2 quark

W*

)

Entries Mean RMS Underflow Overflow Integral

38049 71.59 15.93 0 0 1806

M

inv

(Bjet , 2jetsW) = M

inv

(STOP) - M 1є

300 200

The right edge of the peak of M M
inv

100 00

50

(bjet , 2jetsW) 87 GeV M 1є 80.9 GeV
inv(bjet

100 150 200 250 300 350 400 450 500 GeV
jet

M

inv

(b

, JETS

300 250 200 150 100 50 0 0 50

W*

)

Entries Mean RMS Underflow Overflow Integral

38049 72.8 20.4 0 0 1806

stop

= M 1є + M = 167.9 GeV

, 2jetsW) =

100 150 200 250 300 350 400 450 500 GeV

51

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


The test of the other Scalar top mass
M

M M M

stop 1є 1+

= 200.1 GeV = 80.9 GeV = 159.6 GeV

inv

(b

jet

, JETS

W*

)

Entries Mean RMS Underflow Overflow Integral

19377 92.91 20.13 0 0 509.4

50 40 30 20 10 0 0

50 100 150 200 250 300 350 400 450 500 GeV

Right edge of the peak of Minv (bjet , 2jetW) 120 GeV M 1є 80 GeV Mstop = M 1є+ M є
inv(bjet

509 events S/B = 40
52

, 2jetW) = 200 GeV

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Conclusion
1. The MC (PYTHIA 6.4 + CIRCE 1) study of stop pair production in e+e- collisions was done at S ee = 350, 400, 500, 800, 1000 GeV. The that detailed analysis done at S ee = 500 GeV has shown proposed 3 cutes allow to reach S/B = 143. of the MSTOP from the STOP 2 jetsW ) distribution

2. 3.

A possibility of a good reconstruction peak position of M inv (3 jets, i.e. bjet + is demonstrated.

So, finally, the channel

STOP STOP b 1+ b 1- b b q q' - 1є 1є is very promissing for STOP quark search!
53


Publications
"Pair production of scalar top quarks in e+e- collisions at ILC. " Authors: A.Bartl, W.Majerotto, K.MЖniq, A.N.Skachkova, N.B.Skachkov arXiv: 0804.2125v3, ILC-NOTE-2008-042 "On pair production of scalar top quarks in e+ecollisions at ILC and a possibility of their mass reconstruction" Authors: A.Bartl, W.Majerotto, K.Moenig, A.N.Skachkova, N.B.Skachkov arXiv:0906.3805, Phys.Part.Nucl.Lett.6,:181-189, 2009 54
QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Outback

55

QUARKS'2010 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"


Photon beam characteristics
The monochromaticity of the backscattered photon beams is considerably increased if the mean helicities e and Pc of the electron beam and laser photon beam are chosen such that 2ePc -1. In this case the relative number of hard photons becomes nearly twice as large in the region of the photon energy fraction Y= Ei / Eebeam 0.7-0.85 (i=1,2) and the luminosity in collisions of these photons increases by a factor of 3-4.
56

QFTHEP '2011 A.N.Skachkova. "Stop pair production in polarized QFTHEP '2011 A.N.Skachkova pair production polarized



collisions at ILC" ILC


-energy correlation Y1/Y2 spectra for J=2 enhanced
y
0.9 0.8

Whole spectrum

0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.1 0.2 Mean x 0.308 Mean y 0.3029 0.3313 RMS x RMS y 0.3298 Integral 9.182e+06 0 0 0 0 9182025 0 0 0 0 0.3 0.4 0.5 0.6 0.7 0.8 0.9

y

1

2

1

2

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Mean x 0.2635 Mean y 0.2582 0.3077 RMS x RMS y 0.3054 Integral 1.305e+07 0 0 0 01.30472e+07 0 0 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

y

1
1

0 0

0.9

y

1
1

spectrum above stop pair production threshold

1400 1200 1000 800 600 400 200 0

Mean x 0.7279 Mean y 0.7268 0.1476 RMS x RMS y 0.147 Integral 5e+04 0 0 0 0 50000 0 0 0 0

400 350 300 250 200 150 100 50 0

Mean x 0.527 Mean y 0.5246 RMS x 0.2452 RMS y 0.2453 Integral 5e+04 0 0 0 0 50000 0 0 0 0

NGen

1 y 0.9 0.7 0.8 1 0.6 2 0.80.9 y 0.5 0.60.7 0.4 1 0.3 0.40.5 0.2 0.20.3 0.1 0 0 0.1

NGen

y

2 sig

10.9 0.8 0.9 1 0.7 0.6 0.70.8 0.5 y 1 sig 0.50.6 0.4 0.3 0.30.4 0.2 0.10 0 0.10.2

Polarizations + - /- +

Polarizations + + /- -

QUARKS'2010 A.N.Skachkova.. "Stop pair production in polarized collisions at ILC" QFTHEP '2011 A.N.Skachkova "Stop pair production in polarized collisions at ILC"

57


Cross-section dependence on Mstop
Sigma (M_stop1) at fixed Tan_beta=5
Sigma (mb)

x10 0.6

-10

0.5

0.4

0.3

0.2

0.1

0

100

200

300

400

500

600 700 M_stop1 (GeV)

58

QUARKS'2010 A.N.Skachkova. "Stop pair production in polarized collisions at ILC" QFTHEP '2011


B-quarks distributions
E
180 160 140 120

b

Entries Mean RMS Underflow Overflow Integral

50062 11.41 3.923 0 0 2376
160 140 120 100 80 60 40 20

PT

b

Entries Mean RMS Underflow Overflow Integral

50062 8.506 4.515 0 0 2376

STOP

100 80 60 40 20 00 10 20 30 40 50

60

70

80

90 100 GeV

0 0

10

20

30

40

50

60

70

80

90 100 GeV

3000 2500 2000 1500 1000 500

Eb

Entries Mean RMS Underflow Overflow Integral

2002018 94.13 38.87 0 0 7.19e+04

PT
3500 3000 2500 2000 1500 1000 500

b

Entries Mean RMS Underflow Overflow Integral

2002018 72.92 37.5 0 0 7.19e+04

TOP

0 0

50 100 150 200 250 300 350 400 450 500 GeV

0 0

50 100 150 200 250 300 350 400 450 500 GeV

59

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


B-jets distributions
E
200 180 160 140

b jet

Entries Mean RMS Underflow Overflow Integral

100000 28.32 24.54 0 119.8 4626
240 220 200 180 160 140 120 100 80 60 40 20 0 0

PT

b jet

Entries Mean RMS Underflow Overflow Integral

100000 23.36 22.66 0 51.35 4695

STOP

120 100 80 60 40 20 00 10 20 30 40 50 60

70

80

90 100 GeV

10

20

30

40

50

60

70

80

90 100 GeV

E
3000 2500

bjet

Entries Mean RMS Underflow Overflow

2000000 93.1 39.48 0 0 7.183e+04

PT
3500 3000 2500 2000 1500

bjet

Entries Mean RMS Underflow Overflow Integral

2000000 70.29 36.86 0 0 7.183e+04

TOP

2000 1500 1000 500 0 0

Integral

1000 500 50 100 150 200 250 300 350 400 450 500 GeV 00 50 100 150 200 250 300 350 400 450 500 GeV

60

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


distributions in the signal events
E
70 60 50 40 30 20 10 0 0 20 40 60 80 100 120 140 160 180 200 GeV 400 200 0 0 1 2 3 4 5 6 7 8 9 10 GeV sig_mu Entries Mean RMS Underflow Overflow Integral 49698 47.63 29.07 0 0 2359 1400 1200 1000 800 600

E

dec_mu

Entries Mean RMS Underflow Overflow Integral

131792 0.7958 1.157 0 30.9 6225

PT
90 80 70 60 50 40 30 20 10 0 0

sig_mu

Entries Mean RMS Underflow Overflow Integral

49698 39.67
1200

PT

dec_mu

Entries Mean RMS Underflow Overflow Integral

131792 0.6272 1.034 0 22.31 6233

27.43 0 0 2359
1000 800 600 400 200 0

20

40

60

80 100 120 140 160 180 200 GeV

0

1

2

3

4

5

6

7

8

9

10 GeV

Signal 's

Fake 's
61

QFTHEP '2011 A.N.Skachkova. "Stop pair production in e+e - collisions at ILC"


Supersymmetrical particles classification
Particles
"left" quarks "right" quarks "left" leptons "right" leptons Gluon charged boson Edvdev charged Higgs photon neutral boson Sdfv neutral Higgs Graviton
62

Spin
qL Ѕ +1

R

Particles

Spin

R

QFTHEP `2011 A.N.Skachkova. "Stop pair production in polarized collisions at ILC"