Flavour violating squark and gluino decays at LHC

Flavour violating squark and gluino decays at LHC

K. HidakaTokyo Gakugei University

In collaboration withA. Bartl, H. Eberl, E. Ginina, B. Herrmann, W. Majerotto and W. Porod

(A part of this work is published in Phys. Rev. D84 (2011) 115026; arXiv:1107.2775 [hep-ph].)

ICHEP2012, 6 July 2012, Melbourne

Contents1. Introduction

2. MSSM with Quark Flavour Violation (QFV)

3. Constraints on the MSSM

4. QFV gluino 3-body decays　　 4.1 QFV Benchmark Scenario for gluino decays　　 4.2 Impact of squark generation mixing on gluino 3-body decays　　 4.3 Impact on gluino signals at LHC

5. QFV squark bosonic decays　　 5.1 QFV Benchmark Scenario for Squark decays　　 5.2 Impact of squark generation mixing on squark bosonic

decays　　 5.3 Impact on squark signals at LHC

6. Conclusion

• If weak scale SUSY is realized in nature, gluinos and squarks will have high production rates for masses up to O(1) TeV at LHC.

• The main decay modes of gluinos and squarks are usually assumed to be quark-flavour conserving (QFC).

• However, squark generation mixings can induce quark-flavour violating (QFV) decays of gluinos and squarks.

• Here we study the effect of squark generation mixing on squark and gluino production and decays at LHC in the general MSSM with focus on mixing between 2nd and 3rd generation squarks.

1. Introduction

2. MSSM with QFV• The basic parameters of the MSSM with QFV:

tantanmA ,MM11MM22MM33 ,MM22Q,Q,MM22

U,U, M M22D,D,TTUUTTDD

at Q = 1TeVat Q = 1TeV scale (SPA convention) scale (SPA convention)((u, c, t or d, s, u, c, t or d, s, b)b)

tantan ratio of VEV of the two Higgs doublets <Hratio of VEV of the two Higgs doublets <H00 22>/<H>/<H0011>>

mA : CP odd Higgs boson mass (pole mass)

MM1,1, M M22 ,M ,M3 3 : : 　　 U(1), SU(2),SU(3) gaugino massesU(1), SU(2),SU(3) gaugino masses

higgsino mass parameterhiggsino mass parameter

MM22Q,Q,left squarkleft squarksoft mass matrixsoft mass matrix

MM22UU right up-type squark right up-type squarksoft mass matrixsoft mass matrix

MM22DD right down-type squark right down-type squarksoft mass matrixsoft mass matrix

TTUUtrilinear coupling matrix of up-type squark and Higgs bosontrilinear coupling matrix of up-type squark and Higgs boson

TTDD trilinear coupling matrix of down-type squark and Higgs bosontrilinear coupling matrix of down-type squark and Higgs boson

2,23LM

2

,23EM

23A

32A

L L

R R

L R

R L

　　 QFV parameters in our study are:

MM22Q,Q, 　　 : 　　　　　　　 mixing term

MM22UU 　　 : 　　　　　　　　 mixing term

TTUU 　　 : 　　　　　　　　 mixing term


(Note) We work in the super-CKM basis of squarks. .

LL tc ~~ RR tc ~~ RL tc ~~ LR tc ~~

Recent ATLAS and CMS SUSY searches at 7TeV with ~1-5 fb-1

In a simplified model;

gluino mass > 800 GeV squark mass > 850 GeV (for 1st & 2nd generation squarks)

In the context of the CMSSM (mSUGRA);


Respecting these limits, we assume a gluino mass of about

1 TeV in our analysis

(Note) We also respect the constraint on (mA , tantan) from the recent

MSSM Higgs boson search at LHC [arXiv:1202.4083].


The following constraints are imposed in our analysis in order to respect experimental and theoretical constraints:

(a) Constraints from the B-physics experiments :

(b) LEP limits on sparticle masses

(ex) etc.

(c) The experimental limit on SUSY contributions to the electroweak parameter:

(d) Vacuum stability conditions on trilinear couplings (see J.A. Casas and S. Dimopoulos, Phys. Lett. B 387 (1996) 107 [hep-ph/9606237].)

(ex)

)(|| 22

233

222

2223 mMMhT UQtU u

22122222

2 cos)sin( ZWZHmmmm

GeVm 1031

~

0012.0)( SUSY

(HFAG2010) CL) (95% 10 4.23 < ) s B(b 102.87 -4-4 BABAR)(BELLE, CL) (95% )or e=(with 10 2.60 < ) s B(b <100.60 -6--6

(LHCb) CL) (95% 10 4.5 < ) B(B -9-s

BABAR)(BELLE, CL) (68% 10 0.31) (1.68 = ) B(B -4u

(CDF) CL) (68% ps 0.12 17.77 =M -1Bs

(LHCb) CL) (68% ps 0.11 17.63 =M -1Bs

We take the following scenario as our prototype QFV scenario:

We add QFV parameters (i.e. squark-generation mixing parameters) to this scenario:

MM22Q,Q,MM22

U,U, M M22D,D,TTUUTTDD (

4. QFV gluino 3-body decays

4.1 QFV Benchmark Scenario

< up-squark sector > < down-squark sector >

Prototype QFV scenario

Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~

We add mixing to this scenarioRR tc ~~

TeV3~

TeV2~

TeV1~


Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~

RR tc ~~

In this large mixing scenario all squarks other than are very heavy.So, gluino decay is dominated by virtual exchange.

1~um

2~um

1~u

1~uRR tc ~~

In this large mixing scenario;

• Gluino decay is dominated by virtual exchange contribution.

• is a strong mixture of and .

QFV branching ratio could be very large!

RR tc ~~ 1

~u

1~u Rc~ Rt~

)~~( 01tcgB

QFV gluino decay branching ratio can be very large (up to ~40%) for large mixing parameter !

)~~()~~( 01

01 ctgBtcgB QFV decay BR

mixing parameterRR tc ~~

uRR

23RR tc ~~

uRR

23

BR

(glu

ino

→ 3

-bod

y)

)~~( 01ctgB

4.2 Impact of squark generation mixing on gluino 3-body decays

Contour plots of Contour plots of QFVQFV BR in our BR in our scenario

contours

)~~( 01ctgB


mixing parameterLL tc ~~

The QFV decay branching ratio can be very large (up to ~40%) in a

significant part of the plane allowed by all of the constraints.

)~~( 01ctgB

uRRuLL

2323

This can lead to large QFV effects at LHC!

excluded by data) s B(b

excluded by dataBsM

Gluino pair production and the QFV gluino 3-body decay lead to

QFV gluino signature at LHC :

XctctXggpp )~)(~(~~ 01

01

01

~~ ctg

blbWt

‘top-quark + top-quark + 2 jets + missing-ET + beam-jets‘

‘isolated same sign dilepton + 4 jets + missing-ET + beam-jets‘

Example of QFV gluino signal at LHC

4.3 Impact on gluino signals at LHC

p pgg

c

isolated same sign dilepton

l 'l


c

bb

QFV gluino signal rates at LHC

QFV signal rates such as

can be significant for large mixing parameter at LHC!

mixing parameterRR tc ~~ uRR

23

)~~~~( 01

01 XEccttXccttXggpp mis

T uRR

23RR tc ~~


We add QFV parameters (i.e. squark-generation mixing parameters) to this scenario: M M22

Q,Q,MM22U,U,

MM22D,D,TTUUTTDD (

5. QFV squark bosonic decays5.1 QFV Benchmark Scenario

These weak scale parameters are defined at Q = 1 TeV scale (SPA convention).

(M1, M2 ,M3) = (450, 855, 1000) GeV

= 2400 GeV, tan = 20, mA(pole) = 1500 GeV

(M^2_Q11, M^2_Q22, M^2_Q33) = (2400^2, 2360^2, 1450^2) GeV^2

(M^2_U11, M^2_U22, M^2_U33) = (2380^2, 780^2, 750^2) GeV^2

(M^2_D11, M^2_D22, M^2_D33) = (2380^2, 2340^2, 2300^2) GeV^2 All of TU and TD are zero, except TU = -2160 GeV.

decoupling Higgs scenario

large mixing scenario (large top-trilinear-coupling scenario)

RL tt ~~

Physical masses in the prototype QFV scenario

These masses are fairly insensitive to the QFV parameters.

= 125.5 GeV

- CP-even lighter Higgs boson h0 is SM-like!

- its mass mh0 = 125.5 GeV is in the LHC “possible Higgs signal” range ! : 122 < mh0 < 128GeV.

0hm

GeVmmmAHH

150000

GeVm poleg 1141~



Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~


TeV4.2~

TeV8.0~

TeV14.1~

TeV45.1~

large mixingRL tt ~~


Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~

could be sizable!

TeV4.2~

TeV8.0~

TeV14.1~

TeV45.1~

RR tc ~~ 1

~um

2~um

)~~( 012 huuB

large mass splitting between and !1

~um2

~um

In this large & mixing scenario;

QFV branching ratio can be large!

RR tc ~~ RL tt ~~ LRR tctu ~~~~

~1

LRR ttcu ~~~~~2

02~

0 Hh2

~u

02~

0 HhLR tt ~~

~

1~u

LR tt ~~~

In our scenario "top trilinear coupling“ ( coupling) = TU is large!

coupling is large!

)~~( 012 huuB

02

~~ Htt RL

021

~~ huu


QFV BR can be large!

RR tc ~~ RL tt ~~

LRR tctu ~~~~~1

1~u

01

~

tc /

RR ct ~~~

)~/~( 011 tcuB

QFV BR can be large!)~/~~( 01

0012 htchuuB

QFV squark decay branching ratio can be very large (up to ~50%) for large mixing parameter !

QFV decay BR

uRR

23RR tc ~~

)~~( 012 huuB

)~~( 012 huuB


5.2 Impact of squark generation mixing on squark bosonic decays

QFV squark decay BR can be very large simultaneously for sizable mixing parameter !

QFV decay BR

uRR

23RR tc ~~

)~/~( 011 tcuB

)~/~( 011 tcuB


We have obtained a similar result for dependence of QFV BR and !:

can be very large (up to ~50%) for large mixing parameter !

LR tc ~~

Lt~

Lc~

Rt~uRR

23

uRL

23

uRL

33Rc~

uRL

23

)~~( 012 huuB )~/~( 0

11 tcuB )~~( 0

12 huuB uRL

23

Gluino pair production and the QFV squark bosonic decay can lead to

QFV squark signature at LHC :

)~~()~)(~(

)~)(~()~)(~(~~

01

01

00001

001

01

0122

XhhccttXchtcht

XchuchuXcucuXggpp

‘2 top-quarks + 2 jets + 2 h0 + missing-ET + beam-jets‘

Example of QFV squark signal at LHC

blbWt

‘isolated same sign dilepton + 4 jets + 2 h0 + missing-ET + beam-jets‘

5.3 Impact on squark signals at LHC

p pgg

c


l 'l

c

bb


0h0h

h0 decay branching ratios

• B(h0 tau- tau+) = 9.1%

• B(h0 b b_bar) = 57.3%

• B(h0 photon photon) = 0.52%

• B(h0 W W*) = 22.7%

• B(h0 Z Z*) = 2.5%

h0 is SM-like in our scenario!

QFV squark signal rates at LHC

QFV squark signal rates can be significant

at LHC(14 TeV)!

In our scenario;

- gluino prod. cross section is significant:

~ 80 fb at LHC(14 TeV)!

- can be large (~ 25 %)!

We can expect copious production of

from gluino prod. and decays at LHC(14 TeV)!

)~~( Xggpp )/~~( 2 tcugB

2~u

Our analyses suggest the following:

•One should take into account the possibility of significant

contributions from QFV decays in the squark and gluino

search at LHC.

• Moreover, one should also include QFV squark parameters

(i.e. squark–generation mixing parameters) in the determination

of the basic SUSY parameters at LHC.

6. Conclusion

• We have studied production and decays of squarks and gluinos in the MSSM with

squark generation mixing, especially mixing.

• We have shown that QFV squark and gluino decay branching ratios such as

, , can be very large (up to ~50%) due to

the mixing in a significant region of the QFV parameters despite the

very strong constraints from B meson data.

• This can result in remarkable QFV squark and gluino signal events such as

‘ + beam-jets’ and ‘ + beam-jets’

with a significant rate at LHC(14 TeV).

• These could have an important impact on the search for squarks and gluinos and the MSSM parameter determination at LHC.

LRLR tc //~~

)~~( 01ctgB )~/~( 0

11 tcuB )~~( 012 huuB

misTEccttpp mis

TEhhccttpp 00

LRLR tc //~~

Backup Slides

Flavour violating squark and gluino decays at LHC

K. HidakaTokyo Gakugei University

In collaboration withA. Bartl, H. Eberl, E. Ginina, B. Herrmann, W. Majerotto and W. Porod

(A part of this work is published in Phys. Rev. D84 (2011) 115026; arXiv:1107.2775 [hep-ph].)

ICHEP2012, 6 July 2012, Melbourne

Contents1. Introduction

2. MSSM with Quark Flavour Violation (QFV)


4. QFV gluino 3-body decays　　 4.1 QFV Benchmark Scenario for gluino decays　　 4.2 Impact of squark generation mixing on gluino 3-body decays　　 4.3 Impact on gluino signatures at LHC

5. QFV squark bosonic decays　　 5.1 QFV Benchmark Scenario for Squark decays　　 5.2 Impact of squark generation mixing on squark bosonic

decays　　 5.3 Impact on squark signatures at LHC

6.Impact on squark and gluino search at LHC

7. Conclusion

• If weak scale SUSY is realized in nature, gluinos and squarks will have high production rates for masses up to O(1) TeV at LHC.

• The main decay modes of gluinos and squarks are usually assumed to be quark-flavour conserving (QFC).

• However, the squarks are not necessarily quark-flavour eigenstates.

The flavour mixing in the squark sector may be stronger than that in the quark sector.

In this case quark-flavour violating (QFV) decays of gluinos and squarks could occur.

• Here we study the effect of the mixing of charm-squark and top-squark on the squark and gluino decays at LHC.

1. Introduction(1) Motivation;

(2)Purpose of this work;

• In this work we study the effect of squark generation mixing on squark and gluino production and decays at LHC in the general MSSM with focus on mixing between 2nd and 3rd generation squarks. • Taking into account the constraints from B-physics experiments , we show that various regions in parameter space exist where decays of squarks and/or gluinos into flavour violating final states can have large branching ratios of up to ~ 50%. Here we consider both fermionic and bosonic final states.

• This could have an important impact on the search for squarks and gluinos and the MSSM parameter determination at LHC.

2. MSSM with QFV• The basic parameters of the MSSM with QFV:

tantanmA ,MM11MM22MM33 ,MM22Q,Q,MM22

U,U, M M22D,D,TTUUTTDD

at Q = 1TeV scale (SPA convention)at Q = 1TeV scale (SPA convention)((u, c, t or d, s, u, c, t or d, s, b)b)

tantan ratio of VEV of the two Higgs doublets <Hratio of VEV of the two Higgs doublets <H00 22>/<H>/<H0011>>

mA : CP odd Higgs boson mass (pole mass)

MM1,1, M M22 ,M ,M3 3 : : 　　 U(1), SU(2),SU(3) gaugino massesU(1), SU(2),SU(3) gaugino masses

higgsino mass parameterhiggsino mass parameter

MM22Q,Q,left squarkleft squarksoft mass matrixsoft mass matrix

MM22UU right up-type squark right up-type squarksoft mass matrixsoft mass matrix

MM22DD right down-type squark right down-type squarksoft mass matrixsoft mass matrix

TTUUtrilinear coupling matrix of up-type squark and Higgs bosontrilinear coupling matrix of up-type squark and Higgs boson

TTDD trilinear coupling matrix of down-type squark and Higgs bosontrilinear coupling matrix of down-type squark and Higgs boson

2,23LM

2

,23EM

23A

32A

L L

R R

L R

R L

• We study 　　　　 mixing effect:　　 QFV parameters in our study are:

MM22Q,Q, 　　 : 　　　　　　　 mixing term 　（　　　　　

　 mixing term)

MM22UU 　　 : 　　　　　　　　 mixing term



(Note) We work in the super-CKM basis of squarks: .

tc ~~

LL tc ~~ LL bs~~

RR tc ~~ RL tc ~~ LR tc ~~

)~

,~,~

,~

,~,~

(),~,~,~,~,~,~( RRRLLLRRRLLL bsdbsdtcutcu

Recent ATLAS and CMS SUSY searches at 7TeV with ~1-5 fb-1

In a simplified model;


In the context of the CMSSM (mSUGRA);


Respecting these limits, we assume a gluino mass of about

1 TeV in our analysis

(Note) We also respect the constraint on (mA , tantan) from the recent

MSSM Higgs boson search at LHC [arXiv:1202.4083].


The following constraints are imposed in our analysis in order to respect experimental and theoretical constraints:

(a) Constraints from the B-physics experiments :

(b) LEP limits on sparticle masses

(ex) etc.

(c) The experimental limit on SUSY contributions to the electroweak parameter:

(d) Vacuum stability conditions on trilinear couplings (see J.A. Casas and S. Dimopoulos, Phys. Lett. B 387 (1996) 107 [hep-ph/9606237].)

(ex)

3. Constraints on the MSSM (continued)

)(|| 22

233

222

2223 mMMhT UQtU u

22122222

2 cos)sin( ZWZHmmmm

GeVm 1031

~

0012.0)( SUSY

(HFAG2010) CL) (95% 10 4.23 < ) s B(b 102.87 -4-4 BABAR)(BELLE, CL) (95% )or e=(with 10 2.60 < ) s B(b <100.60 -6--6

(LHCb) CL) (95% 10 4.5 < ) B(B -9-s

BABAR)(BELLE, CL) (68% 10 0.31) (1.68 = ) B(B -4u

(CDF) CL) (68% ps 0.12 17.77 =M -1Bs

(LHCb) CL) (68% ps 0.11 17.63 =M -1Bs

(Note) We find that these constraints are very important:

and data => strongly constrain the QFV squark parameters

data => strongly constrain the QFV squark parameters

data => strongly constrain

Vacuum stability conditions => strongly constrain QFV trilinear couplings TUTD

sBM) s B(b

) B(Bu )tan,( Hm

(Note) We use the public code SPheno v3.1 in the calculation of the B-physics observables.

) B(B -s


We add QFV parameters (i.e. squark-generation mixing parameters) to this scenario:

MM22Q,Q,MM22

U,U, M M22D,D,TTUUTTDD (

4. QFV gluino 3-body decays

4.1 QFV Benchmark Scenario



(Note) We can easily push up to 125 GeV without changing

our final conclusion, for example, by taking

and !

0hm

20tan GeVm

A15000



Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~


TeV3~

TeV2~

TeV1~


“Prototype QFV scenario” + “large mixing”

Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~

RR tc ~~

In this large mixing scenario all squarks other than are very heavy.So, gluino decay is dominated by virtual exchange.

1~um

2~um

RR tc ~~

1~u

1~uRR tc ~~

In this large mixing scenario;

• Gluino decay is dominated by virtual exchange contribution.

• is a strong mixture of and .

QFV branching ratio could be very large!

RR tc ~~ 1

~u

1~u Rc~ Rt~

)~~( 01tcgB

We study the effect of squark generation mixing on gluino production and decays

at LHC for the case that the gluino is lighter than all squarks and dominantly

decays into three particles:

In case of mixing, gluino could decay as follows:

4.2 Impact of squark generation mixing on gluino 3-body decays

tc ~~

0~~iqqg jqqg ~'~

01

~~ tcg 01

~~ ctg

• Gluino decay branching ratios in our scenario:

QFV gluino decay branching ratio can be very large (up to ~40%) for large mixing parameter !

)~~()~~( 01

01 ctgBtcgB QFV decay BR


uRR

23RR tc ~~

uRR

23

BR

(glu

ino

→ 3

-bod

y)

)~~( 01ctgB


contours

)~~( 01ctgB



The QFV decay branching ratio can be very large in a significant part of

the plane allowed by all of the constraints.

)~~( 01ctgB

uRRuLL

2323



contours

)~~( 01ctgB



The QFV decay branching ratio can be very large in a significant part of

the plane allowed by all of the constraints.

)~~( 01ctgB

uRRuLL

2323


excluded by data) s B(b

excluded by dataBsM

We have obtained a similar result for the QFV 3-body decay branching ratio :

It can be as large as ~35%!

)~~()~~()~~( 01

01

01 bsgBbsgBbsgB

Neutralino/chargino parameter dependence of QFV BR

The branching ratios of the QFV 3-particle gluino decays depend quite strongly on the parameters of the neutralino/chargino sector!

contours in – M2 plane )~~( 01ctgB

4.3 Impact on gluino signatures at LHC

01

~~ ctg

The signature of the QFV gluino decay at LHC:

' top-quark + jet + missing-energy'

Large mixing RR tc ~~

Large QFV BR )~~( 01ctgB

01

~~ ctg

g~ c

t

01

~

Gluino pair production and the QFV gluino 3-body decay lead to

QFV gluino signature at LHC :

XctctXggpp )~)(~(~~ 01

01

01

~~ ctg

blbWt

‘top-quark + top-quark + 2 jets + missing-ET + beam-jets‘





c

p p

gg

g

t

g~g~

tc

01

~0

1~

b bW

l

W

'l

jetbeam jetbeam

QFV gluino decay


p pgg

c


l 'l


c

bb

QFV gluino signal rates at LHC

QFV signal rates such as

can be significant for large mixing parameter at LHC!

mixing parameterRR tc ~~ uRR

23

)~~~~( 01

01 XEccttXccttXggpp mis

T uRR

23RR tc ~~


We add QFV parameters (i.e. squark-generation mixing parameters) to this scenario: M M22

Q,Q,MM22U,U,

MM22D,D,TTUUTTDD (

5. QFV squark bosonic decays5.1 QFV Benchmark Scenario

These weak scale parameters are defined at Q = 1 TeV scale (SPA convention).

(M1, M2 ,M3) = (450, 855, 1000) GeV

= 2400 GeV, tan = 20, mA(pole) = 1500 GeV

(M^2_Q11, M^2_Q22, M^2_Q33) = (2400^2, 2360^2, 1450^2) GeV^2

(M^2_U11, M^2_U22, M^2_U33) = (2380^2, 780^2, 750^2) GeV^2

(M^2_D11, M^2_D22, M^2_D33) = (2380^2, 2340^2, 2300^2) GeV^2 All of TU and TD are zero, except TU = -2160 GeV.

decoupling Higgs scenario

large mixing scenario (large top-trilinear-coupling scenario)

RL tt ~~



= 125.5 GeV

- CP-even lighter Higgs boson h0 is SM-like!

- its mass mh0 = 125.5 GeV is in the LHC “possible Higgs signal” range ! : 122 < mh0 < 128GeV.

0hm

GeVmmmAHH

150000

GeVm poleg 1141~



Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~

We add mixing to this scenarioLRLR tc //~~

TeV4.2~

TeV8.0~

TeV14.1~

TeV45.1~

large mixingRL tt ~~


Rum~

gm~

Lum~

Lcm~

Ltm~

Rbm~

Rdm~

Rsm~

gm~

Ldm~

Lsm~

Lbm~

Rtm~

Rcm~

could be sizable!

TeV4.2~

TeV8.0~

TeV14.1~

TeV45.1~

RR tc ~~ 1

~um

2~um

)~~( 012 huuB

large mass splitting between and !1

~um2

~um


QFV branching ratio can be large!

RR tc ~~ RL tt ~~ LRR tctu ~~~~

~1

LRR ttcu ~~~~~2

02~

0 Hh2

~u

02~

0 HhLR tt ~~

~

1~u

LR tt ~~~

In our scenario "top trilinear coupling“ ( coupling) = TU is large!

coupling is large!

)~~( 012 huuB

02

~~ Htt RL

021

~~ huu


QFV BR can be large!

RR tc ~~ RL tt ~~

LRR tctu ~~~~~1

1~u

01

~

tc /

RR ct ~~~

)~/~( 011 tcuB

QFV BR can be large!)~/~~( 01

0012 htchuuB

5.2 Impact of squark generation mixing on squark bosonic decays

large & mixings

RR tc ~~ RL tt ~~

large QFV BR’s & !)~~( 012 huuB )~/~( 0

11 tcuB


• Squark decay branching ratios in our scenario:

QFV squark decay branching ratio can be very large (up to ~50%) for large mixing parameter !

QFV decay BR

uRR

23RR tc ~~

)~~( 012 huuB

)~~( 012 huuB



QFV squark decay BR can be very large simultaneously for sizable mixing parameter !

QFV decay BR

uRR

23RR tc ~~

)~/~( 011 tcuB

)~/~( 011 tcuB


We have obtained a similar result for dependence of QFV BR and !:

can be very large (up to ~50%) for large mixing parameter !

LR tc ~~

Lt~

Lc~

Rt~uRR

23

uRL

23

uRL

33Rc~

uRL

23

)~~( 012 huuB )~/~( 0

11 tcuB )~~( 0

12 huuB uRL

23


QFV squark decay BR can be very large (up to ~50%) for large mixing parameter !

QFV decay BR

uRL

23LR tc ~~ )~~( 0

12 huuB

)~~( 012 huuB

mixing parameterLR tc ~~

QFV parameters: = (227 GeV)2 = (433 GeV)2

223QM

223UM

233

22232223

/)2/( QUU

uRLMMTv


QFV squark decay BR can be very large simultaneously for large mixing parameter !

QFV decay BR )~/~( 011 tcuB

)~/~( 011 tcuB

LR tc ~~ uRL

23

QFV parameters: = (227 GeV)2 = (433 GeV)2

mixing parameterLR tc ~~ 233

22232223

/)2/( QUU

uRLMMTv

5.3 Impact on squark signatures at LHC

01

~~ ctg Large , , mixings RR tc ~~ RL tt ~~ LR tc ~~

Large QFV BR )~/~~( 01

0012 htchuuB

QFV squark signals with significant rate at LHC !


QFV squark signal at LHC :

)~~()~)(~(

)~)(~()~)(~(~~

01

01

0001

01

01121

XhcctcXchtcc

XchucuXcucuXggpp

‘top-quark + 3 jets + h0 + missing-ET + beam-jets‘



QFV squark signal at LHC :

)~~()~)(~(

)~)(~()~)(~(~~

01

01

0001

01

01121

XhccttXchttc

XchutuXcutuXggpp

‘2 top-quarks + 2 jets + h0 + missing-ET + beam-jets‘


blbWt

‘isolated same sign dilepton + 4 jets + h0 + missing-ET + beam-jets‘


QFV squark signature at LHC :

)~~()~)(~(

)~)(~()~)(~(~~

01

01

00001

001

01

0122

XhhccttXchtcht

XchuchuXcucuXggpp

‘2 top-quarks + 2 jets + 2 h0 + missing-ET + beam-jets‘


blbWt


p pgg

c


l 'l

c

bb


0h0h

h0 decay branching ratios

• B(h0 tau- tau+) = 9.1%

• B(h0 b b_bar) = 57.3%

• B(h0 photon photon) = 0.52%

• B(h0 W W*) = 22.7%

• B(h0 Z Z*) = 2.5%

h0 is SM-like in our scenario!

QFV signal rates at LHC

QFV squark signal rates can be significant

at LHC(14 TeV)!

In our scenario;

- gluino prod. cross section is significant:

~ 80 fb at LHC(14 TeV)!

- can be large (~ 25 %)!

We can expect copious production of

from gluino prod. and decays at LHC(14 TeV)!

)~~( Xggpp )/~~( 2 tcugB

2~u

Our analyses suggest the following:

•One should take into account the possibility of significant

contributions from QFV decays in the squark and gluino

search at LHC.

• Moreover, one should also include QFV squark parameters

(i.e. squark–generation mixing parameters) in the determination

of the basic SUSY parameters at LHC.

6. Impact on squark & gluino search at LHC

7. Conclusion• We have studied the effect of squark generation mixing on squark and gluino

production and decays at LHC in the MSSM with focus on mixing between 2nd

and 3rd generation squarks.

• Taking into account the constraints from B-physics experiments, we have shown that

various regions in parameter space exist where decays of squarks and/or gluinos

into flavour violating final states can have large branching ratios of up to ~ 50%.

Here we have considered both fermionic and bosonic final states.

• Rates of the corresponding signals, e.g. ‘ + beam-jets’ , and

‘ + beam-jets’ can be significant at LHC(14 TeV).

• We conclude that the inclusion of flavour mixing effects can be important for the

search of squarks and gluinos and the determination of the MSSM parameters

at LHC.

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Flavour violating squark and gluino decays at LHC