light stop in precise top sample - university of wisconsin ...wangkai/lanzhou.pdfhiggs-likeíp!...

Light Stop in Precise Top Sample

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Event display of a H ! e+e�µ+µ� candidate event with M4` = 122.6(123.9) GeV without (with) Z mass

constraint. The masses of the lepton pairs are 87.9 GeV and 19.6 GeV. The event was recorded by ATLAS on

18-Jun-2012, 11:07:47 CEST in run number 205113 as event number 12611816. Muon tracks are colored red,

electron tracks and clusters in the LAr calorimeter are colored green. The larger inset shows a zoom into the

tracking detector. The smaller inset shows a zoom into the vertex region, indicating that the 4 leptons originate from

the same primary vertex. (Courtesy: ATLAS, Collaboration)

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51 Lepton-Photon, 24–29 June, 2013 Andreas Hoecker — Searches for Supersymmetry at Colliders

ATLAS deeply mines SUSY signatures & models

51 Model e, µ, �, � Jets Emiss

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MSUGRA/CMSSM 1 e,µ 3-6 jets Yes 20.3 any m(q) ATLAS-CONF-2013-0621.2 TeVg

MSUGRA/CMSSM 0 7-10 jets Yes 20.3 any m(q) ATLAS-CONF-2013-0541.1 TeVg

qq, q�q�01 0 2-6 jets Yes 20.3 m(�

01)=0 GeV ATLAS-CONF-2013-047740 GeVq

g g , g�qq�01 0 2-6 jets Yes 20.3 m(�

01)=0 GeV ATLAS-CONF-2013-0471.3 TeVg

g g , g�qq�±1�qqW ±�01 1 e,µ 3-6 jets Yes 20.3 m(�

01)<200 GeV, m(�

±)=0.5(m(�

01 )+m(g )) ATLAS-CONF-2013-0621.18 TeVg

g g�qqqq��(��)�01�

01 2 e,µ (SS) 3 jets Yes 20.7 m(�

01)<650 GeV ATLAS-CONF-2013-0071.1 TeVg

GMSB (� NLSP) 2 e,µ 2-4 jets Yes 4.7 tan�<15 1208.46881.24 TeVg

GMSB (� NLSP) 1-2 � 0-2 jets Yes 20.7 tan� >18 ATLAS-CONF-2013-0261.4 TeVg

GGM (bino NLSP) 2 � 0 Yes 4.8 m(�01)>50 GeV 1209.07531.07 TeVg

GGM (wino NLSP) 1 e, µ + � 0 Yes 4.8 m(�01)>50 GeV ATLAS-CONF-2012-144619 GeVg

GGM (higgsino-bino NLSP) � 1 b Yes 4.8 m(�01)>220 GeV 1211.1167900 GeVg

GGM (higgsino NLSP) 2 e, µ (Z ) 0-3 jets Yes 5.8 m(H)>200 GeV ATLAS-CONF-2012-152690 GeVg

Gravitino LSP 0 mono-jet Yes 10.5 m(g )>10�4 eV ATLAS-CONF-2012-147645 GeVF1/2 scale

g�bb�01 0 3 b Yes 20.1 m(�


g�tt �01 0 7-10 jets Yes 20.3 m(�

01) <200 GeV ATLAS-CONF-2013-0541.14 TeVg

g�tt �01 0-1 e,µ 3 b Yes 20.1 m(�


g�bt �+1 0-1 e,µ 3 b Yes 20.1 m(�


b1b1, b1�b�01 0 2 b Yes 20.1 m(�

01)<100 GeV ATLAS-CONF-2013-053100-630 GeVb1

b1b1, b1�t�±1 2 e,µ (SS) 0-3 b Yes 20.7 m(�

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01) ATLAS-CONF-2013-007430 GeVb1

t1 t1(light), t1�b�±1 1-2 e,µ 1-2 b Yes 4.7 m(�

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t1 t1(light), t1�Wb�01 2 e,µ 0-2 jets Yes 20.3 m(�

01) =m(t1)-m(W )-50 GeV, m(t1)<<m(�

±1 ) ATLAS-CONF-2013-048220 GeVt1

t1 t1(medium), t1�b�±1 2 e,µ 0-2 jets Yes 20.3 m(�

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±1 )=10 GeV ATLAS-CONF-2013-048150-440 GeVt1

t1 t1(medium), t1�b�±1 0 2 b Yes 20.1 m(�

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01 )=5 GeV ATLAS-CONF-2013-053150-580 GeVt1

t1 t1(heavy), t1�t�01 1 e,µ 1 b Yes 20.7 m(�

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t1 t1(heavy), t1�t�01 0 2 b Yes 20.5 m(�

01)=0 GeV ATLAS-CONF-2013-024320-660 GeVt1

t1 t1(natural GMSB) 2 e, µ (Z ) 1 b Yes 20.7 m(�01)>150 GeV ATLAS-CONF-2013-025500 GeVt1

t2 t2, t2�t1 + Z 3 e, µ (Z ) 1 b Yes 20.7 m(t1)=m(�01)+180 GeV ATLAS-CONF-2013-025520 GeVt2

�L,R�L,R, ��01 2 e,µ 0 Yes 20.3 m(�01)=0 GeV ATLAS-CONF-2013-04985-315 GeV�

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01)=0 GeV, m(�, �)=0.5(m(�

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1

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+1��(��) 2 � 0 Yes 20.7 m(�

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±1 )+m(�

01)) ATLAS-CONF-2013-028180-330 GeV�±

1

�±1 �02��L��L�(��), ��L�(��) 3 e,µ 0 Yes 20.7 m(�

±1 )=m(�

02), m(�

01)=0, m(�, �)=0.5(m(�

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01 )) ATLAS-CONF-2013-035600 GeV�±

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01 3 e,µ 0 Yes 20.7 m(�

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02 ), m(�

01)=0, sleptons decoupled ATLAS-CONF-2013-035315 GeV�±

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Direct �+1 ��1 prod., long-lived �

±1 0 1 jet Yes 4.7 1<�(�

±1 )<10 ns 1210.2852220 GeV�±

1

Stable, stopped g R-hadron 0 1-5 jets Yes 22.9 m(�01)=100 GeV, 10 µs<�(g)<100 s ATLAS-CONF-2013-057857 GeVg

GMSB, stable � 1-2 µ 0 - 15.9 5<tan�<50 ATLAS-CONF-2013-058385 GeV�

Direct �� prod., stable � or � 1-2 µ 0 - 15.9 m(�)=m(�) ATLAS-CONF-2013-058395 GeV�

GMSB, �01��g , long-lived �

01 2 � 0 Yes 4.7 0.4<�(�

01)<2 ns 1304.6310230 GeV�0

1

�01�qqµ (RPV) 1 µ 0 Yes 4.4 1 mm<c�<1 m, g decoupled 1210.7451700 GeVq

LFV pp�� + X , ��e + µ 2 e,µ 0 - 4.6 ��311=0.10, �132=0.05 1212.12721.61 TeV��LFV pp�� + X , ��e(µ) + � 1 e,µ + � 0 - 4.6 ��311=0.10, �1(2)33=0.05 1212.12721.1 TeV��

Bilinear RPV CMSSM 1 e,µ 7 jets Yes 4.7 m(q)=m(g ), c�LSP<1 mm ATLAS-CONF-2012-1401.2 TeVq, g

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1

g�qqq 0 6 jets - 4.6 1210.4813666 GeVg

g�t1t, t1�bs 2 e,µ (SS) 0-3 b Yes 20.7 ATLAS-CONF-2013-007880 GeVg

Scalar gluon 0 4 jets - 4.6 incl. limit from 1110.2693 1210.4826100-287 GeVsgluon

WIMP interaction (D5, Dirac �) 0 mono-jet Yes 10.5 m(�)<80 GeV, limit of<687 GeV for D8 ATLAS-CONF-2012-147704 GeVM* scale

Mass scale [TeV]10�1 1�

s = 7 TeVfull data

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partial data

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ATLAS SUSY Searches* - 95% CL Lower LimitsStatus: LP 2013

ATLAS Preliminary�L dt = (4.4 - 22.9) fb�1

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*Only a selection of the available mass limits on new states or phenomena is shown. All limits quoted are observed minus 1� theoretical signal cross section uncertainty.

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= m±

1χ∼

m100 200 300 400 500 600 700

[G

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0 1χ∼m

0

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400

600

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)=0.5)-l+l, BF(Ll~, ( ±

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-1 = 9.2 fbint = 8 TeV, LsCMS Preliminary

01χ∼

+ 0.5m±

1χ∼

= 0.5ml~ m

01χ∼ > m

±1χ∼ = m

02χ∼ m

Searches for “Natural” SUSY scenarios

Electroweak neutralino, chargino and slepton pair production

Most recent CMS references (8 TeV): PAS-SUS-12-022 Most recent ATLAS references (8 TeV): ATLAS-CONF-2013-049, ATLAS-CONF-2013-036,

ATLAS-CONF-2013-035, ATLAS-CONF-2013-028

Associated chargino-neutralino production (in particular in the WZ+MET final state) benefits from combined analysis of 2 and 3 leptons as featured by CMS including also tau leptons

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Searches for “Natural” SUSY scenarios

Direct stop pair production — grand summary for top+LSP

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< 30 GeV dependence on L/R stop admixture

(ãÇ˘ p et alåN0õ et al)


2b + ` + nj +��ET


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10-2

10-1

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150 175 200 225 250 275 300Mt (GeV)

m (p

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(Mt = 200) ' 0.2 pb


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mt = 173.2 GeV¯8K �t � ⇤QCD

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2

4

6

8

10

12

14

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NLO + NNLL

0 0.2 0.4 0.6 0.8 10

100

200

300

400

d�/d

�t[pb]

�t

�s = 7 TeV

Figure 11: Distributions d�/d�t at the Tevatron (left) and LHC (right).

NLO + NNLL

CDF data

0 200 400 600 800 1000 12000.01

0.1

1

10

100

M [GeV]

d�/d

M[fb/G

eV

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NLO + NNLL

CDF data

360 380 400 420 440 460 480 5000

10

20

30

40

50

60

70

80

M [GeV]

d�/d

M[fb/G

eV

]

�s = 1.96 TeV

Figure 12: Comparison of the RG-improved predictions for the invariant mass spectrum with

CDF data [9]. The value mt = 173.1 GeV has been used. No fit to the data has been performed.

very useful distribution d�/d�t, with �t defined as in (4). A simple change of variables yields

d�

d�t=

2mt�t

(1 � �2t )

32

d�

dM. (106)

The resulting spectra for the Tevatron and LHC, obtained using RG-improved perturbation

theory, are shown in Figure 11. As before, the distributions are normalized such that the area

under the curves corresponds to the total cross section. Recall that the physical meaning of

the variable �t is that of the 3-velocity of the top quarks in the t¯t rest frame. The distributions

show that the dominant contributions to the cross section arise from the region of relativistic

top quarks, with velocities of order 0.4–0.8 at the Tevatron and 0.5–0.9 at the LHC. We will

come back to the significance of this observation in the next section.

In Figure 12, we compare our RG-improved prediction for the invariant mass spectrum

36

In order to analyze the electroweak O!!2s!" terms, it

is useful to separate the QED contributions involvingphotons from the weak contributions with Z bosons. Inthe QED sector we obtain the O!!2

s!" contributions toN from three classes of partonic processes: q !q ! t!t,q !q ! t!tg and q !q ! t!t". The first case is the virtual-photon contribution, which can be obtained from theQCD analogue, namely, the O!!3

s" interference of boxand tree-level amplitudes, by substituting successively

each one of the three internal gluons by a photon, asdisplayed in Fig. 4.The essential differences between the calculation of the

O!!3s" and of QED O!!2

s!" terms are the coupling con-stants and the appearance of the SU!3" generators in thestrong vertices. Summing over color in the final state andaveraging in the initial state we find for the virtual contri-butions to the antisymmetric cross section the followingratio,

jMt!tj2O!!2s!";asym

jMt!tj2O!!3s ";asym

#2Re!Mt!t

O!!"Mt!t $O!!2

s ""asym % 2Re!Mt!tO!!s"M

t!t $O!!s!""asym

2Re!Mt!tO!!s"M

t!t $O!!2

s ""asym#

Ft!tQED!!s;!; Qt; Qq"

Ft!tQCD!!s"

(8)

that can be expressed in terms of two factors Ft!tQED and Ft!t

QCD depending only on coupling constants and color traces,

Ft!tQCD # g6s

9#AD#BF#EC Tr!tAtBtC"

!1

2Tr!tDtEtF" % 1

2Tr!tDtFtE"

"# g6s

16 & 9 d2; (9a)

Ft!tQED # nt!t

#g4se

2QqQt

9#AC#BD Tr!tAtB"Tr!tCtD"

$# 6g4se

2

9QtQq: (9b)

Ft!tQCD contains two different color structures and the result

depends on d2 # dABCdABC # 403 , which arises from

Tr!tAtBtC" # 14 !ifABC % dABC". Ft!t

QED instead depends onthe charges of the incoming quarks (Qq) and of the top-quark (Qt), together with nt!t # 3 corresponding to Fig. 4.

In a similar way, also the real-radiation processes q !q !t!tg and q !q ! t!t" (Figs. 5 and 6) can be evaluated startingfrom the result obtained for q !q ! t!tg in the QCD case andsubstituting successively each gluon by a photon, yieldingthe ratios

jMt!tgj2O!!2s!";asym

jMt!tgj2O!!3s ";asym

#2Re!Mt!tg

O!! %%%%!s

p "Mt!tg $O!!s

%%%%!s

p ""asymjMt!tg

O!!s%%%%!s

p "j2

asym

#Ft!tgQED!!s;!; Qt; Qq"

Ft!tgQCD!!s"

; (10)

jMt!t"j2O!!2s!";asym

jMt!tgj2O!!3s ";asym

#jMt!t"

O!!s%%%!

p "j2

asym

jMt!tgO!!s

%%%%!s

p "j2

asym

#Ft!t"QED!!s;!; Qt; Qq"

Ft!tgQCD!!s"

: (11)

Ft!tgQCD, F

t!tgQED and Ft!t"

QED are related to Ft!tQCD, F

t!tQED in the

following way,

Ft!tgQCD # Ft!t

QCD; Ft!tgQED # 2

3Ft!tQED;

Ft!t"QED # 1

3Ft!tQED; Ft!t

QED # Ft!tgQED % Ft!t"

QED: (12)

This guarantees the cancellation of the IR singularitiesstemming from the virtual contributions.The O!!2

s!" antisymmetric term from q !q ! t!tg comesfrom the interference of q !q ! g ! t!tg (Fig. 3) and q !q !" ! t!tg (Fig. 5). It can be obtained from the correspondingQCD result with the replacement of one gluon by a photonand the right couplings, as done in the case of q !q ! t!t. Theonly difference is the number of gluons to be replaced: in

FIG. 5. Real gluon emission from photon exchange diagrams.

FIG. 4. Different ways of QED—QCD interference atO!!2

s!".

ELECTROWEAK CONTRIBUTION TO THE TOP QUARK . . . PHYSICAL REVIEW D 84, 093003 (2011)

093003-3pÿ¿åHiggs:6


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mb ⌧ mt

Wµ⌘Å� ✏0 ⇠ kµ/mW

✏⇤0ubL�µut ' mt

mWubLut

F0 =

�(t ! bW+0 )

�(t ! bW+0 ) + �(t ! bW+

+ ) + �(t ! bW+� )

' 70%

F� ' 30%, F+ ' 0


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1

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d�

d cos ✓⇤=

3

8

FR(1 + cos ✓⇤)2 +

3

8

FL(1 � cos ✓⇤)2 +

3

4

F0 sin

2 ✓⇤

(p`T¯s')


✓ÑI˜öI

the angle between the momentum direction of chargedlepton from the W-boson decay and the reversedmomentum direction of the b quark from top-quark decay ,both boost into the w-boson rest framethe angle between the charged lepton three-momentum inthe W rest frame and the the W momentum in the top restframethe angle between the direction of the charged lepton andthe reversed direction of the top quark ,both in the restframe of the W bosonthe angle between the momentum direction of the chargedlepton from the W-boson decay and reversed momentumdirection of the b quark from top-quark decay


WÅ�Kœ�Higgs:6

22 M. Aldaya

W polarization (2.2 fb-1) Anomalous contributions to the tWb vertex change the probabilities of the W helicity states

CMS-PAS TOP-11-020

!  In SM: 3 possible W helicity states: F0 (longitudinal) ~ 0.70, FL (left) ~ 0.30, FR (right) ~ 0

Angle between charged lepton and top direction in W rest frame

!  Helicity fractions extracted from maximum likelihood fit:

•  1 isolated high-pT µ, ! 4 jets, ! 1 b-tag •  Kinematic fit to reconstruct ttbar system

!  Good agreement with SM !  Similar precision as previous measurements (Tevatron, ATLAS)

!  Measure sensitive variable, cos("*), in muon+jets channel:

F0

FR FR

XXVI Rencontres de la Vallee d'Aoste, 01.03.12

Feb’12

LHC Combination

FL = 0.359 ± 0.021(stat.) ± 0.028(syst.)F0 = 0.626 ± 0.034(stat.) ± 0.048(syst.)


Stop˚fl


{[�gV11˜tL + ytV12˜tR]

¯bPR + ybU12˜tL¯bPL}�+c1

Natural SUSY in MSSM ! Large A (50% Left-Right)But NMSSM gives more freedom.


ØWino


ØHiggsino


ãã ÷ v8KÕ˙(�2)

No b-tagging~p⌫

T = ��~pT

Scan p⌫z : -3500 GeV –3500 GeV

�2=

(M`⌫ja � mt)2

�2t

+

(Mjbjcjd � mt)2

�2t

+

(M`⌫ � mW )

2

�2W

+

(Mjcjd � mW )

2

�2W

mt = 172.5 GeV, mW = 80.4 GeV, �t = 14 GeV, �W = 10 GeV


cos ✓

e, bˆ(œÅP

pe · pb ' 1

2

M2eb

cos ✓⇤e+ =

EeEb � pe · pb

| pe || pb | = �1 +

pe · pb

EeEb= �1 +

M2eb

2EeEb

⌥∆!ãv8Kpÿ�W(√˚- Eb = (m2t � m2

W )/2mW ,E` = mW /2

cos ✓⇤ = �1 +

2M2eb

m2t � m2

W


cos ✓:Correct vs. Fake

ecos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Even

ts

0

200

400

600

800

1000

1200

1400

is right-handed1 and t2mu>>M

Real Combination

Combination2r

ecos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1Ev

ents

0

200

400

600

800

1000

is right-handed1 and t2mu<<M

Real Combination

Combination2r


Correct vs. Fake

blM

0 50 100 150 200 250

Even

ts

0

1000

2000

3000

4000

5000


Real Combination

Combination2r

blM

0 50 100 150 200 250Ev

ents

0

1000

2000

3000

4000

5000


Real Combination

Combination2r


Correct vs. Fake

lE

0 20 40 60 80 100 120 140

Even

ts

0

2000

4000

6000

8000

10000

12000


chargino rest frame

fake W rest frame

lE

0 20 40 60 80 100 120 140Ev

ents

0

2000

4000

6000

8000

10000

12000


chargino rest frame

fake W rest frame


Correct vs. Fake

bE

0 50 100 150 200 250 300

Even

ts

0

10000

20000

30000

40000

50000


chargino rest frame

fake W rest frame

bE

0 50 100 150 200 250 300Ev

ents

0

10000

20000

30000

40000

50000


chargino rest frame

fake W rest frame


Correct vs. Fake

lEbE

0 20 40 60 80 100 120 140

Even

ts

0

2000

4000

6000

8000

10000


chargino rest frame

fake W rest frame

lEbE

0 20 40 60 80 100 120 140Ev

ents

0

2000

4000

6000

8000

10000


chargino rest frame

fake W rest frame


�2åv8K(œ ÷

*ecos-1 -0.5 0 0.5 1

num

ber o

f eve

nts

0

2000

4000

6000

8000

10000

=200t-fake m2r*-L 1t~1

t~ µparton_level M2>>

*ecos-1 -0.5 0 0.5 1

num

ber o

f eve

nts

0

5000

10000

15000

20000

25000

=400t-fake m2r*-L 1t~1


*ecos-1 -0.5 0 0.5 1

num

ber o

f eve

nts

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

=1000t-fake m2r*-L 1t~1



”∫

vÜ⌥œv8K(Stop)êœ(v8K˘˚fl-ÑÔ˝�—∞‡:fakeÕ˙ÑqÕ�Çú g∞ ÑKœWÅ�Ñπ’�⌥œv8Kh∞:ÊKÅ�ÑW�v�⇢À;´íd⇥

ecos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Even

ts

0

200

400

600

800

1000

1200

1400


Real Combination

Combination2r

ecos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Even

ts

0

200

400

600

800

1000


Real Combination

Combination2r

""'∂�


light stop in precise top sample - university of wisconsin ...wangkai/lanzhou.pdfhiggs-likeíp!...

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