Changes between Version 1 and Version 2 of TopBSM


Ignore:
Timestamp:
04/06/12 16:33:02 (7 years ago)
Author:
trac
Comment:

--

Legend:

Unmodified
Added
Removed
Modified
  • TopBSM

    v1 v2  
    33== Model for BSM physics studies in ttbar production ([http://arxiv.org/abs/0712.2355 arxiv:0712.2355]) Version 1.3 ==
    44
    5 The {{{topBSM}}} is a model implemented to study BSM effects in the ttbar invariant mass spectrum. This model includes the following possible resonances in the ttbar spectrum:
     5The {{{
     6topBSM
     7}}} is a model implemented to study BSM effects in the ttbar invariant mass spectrum. This model includes the following possible resonances in the ttbar spectrum:
    68   * spin-0, color singlet
    79   * spin-0, color octet
     
    1113   * spin-2, RS model
    1214
    13 Note that this {{{topBSM}}} model can only be used for ttbar production. Any other final state might lead to inconsistencies in the evaluation of the diagrams. This model uses a special {{{param_card.dat}}} and {{{run_card.dat}}} that can be found [attachment:param_card.dat here] and [attachment:run_card.dat here].
     15Note that this {{{
     16topBSM
     17}}} model can only be used for ttbar production. Any other final state might lead to inconsistencies in the evaluation of the diagrams. This model uses a special {{{
     18param_card.dat
     19}}} and {{{
     20run_card.dat
     21}}} that can be found [attachment:param_card.dat here] and [attachment:run_card.dat here].
    1422
    1523=== spin-0, color singlet ===
     
    1725([attachment:proc_card.dat proc_card.dat]: topBSM spin-0 color singlet proc_card.dat)
    1826
    19 The spin-0, color singlet particle, in the {{{topBSM}}} called {{{s0}}} (PDG code: 6000045), is a Higgs-like particle that couples only to top quarks. The production of the spin-0 is only through a top quark loop by gluon fusion. And its decay is directly to two top quarks with a branching ratio %$\textrm{BR}(s0\to t\bar{t})=1$%.
    20 
    21 It's coupling strength to the top quark is by default equal to the SM Higgs coupling to top quarks, ''i.e.'', %$im_t/v$%, but this can be changed in the {{{param_card.dat}}}. In the {{{param_card.dat}}} there are the following two lines:
     27The spin-0, color singlet particle, in the {{{
     28topBSM
     29}}} called {{{
     30s0
     31}}} (PDG code: 6000045), is a Higgs-like particle that couples only to top quarks. The production of the spin-0 is only through a top quark loop by gluon fusion. And its decay is directly to two top quarks with a branching ratio $\textrm{BR}(s0\to t\bar{t})=1$.
     32
     33It's coupling strength to the top quark is by default equal to the SM Higgs coupling to top quarks, ''i.e.'', %$im_t/v$%, but this can be changed in the {{{
     34param_card.dat
     35}}}. In the {{{
     36param_card.dat
     37}}} there are the following two lines:
    2238{{{
    2339         1.     1.00000000e+00   # s0scalarf  ,spin-0 scalar mult.fac.
     
    2541}}}
    2642
    27 These two values correspond to multiplication factors for the coupling strength, ''i.e.'', %$g_{s0tt}=$% {{{s0scalarf}}} %$i\frac{m_t}{v}+$% {{{s0axialf}}} %$\frac{m_t}{v}\gamma_5$%. Hence, the spin-0 can be a scalar or a pseudo-scalar or a mixed CP state by playing around with these two factors.
    28 
    29 Due to the loop in the production mechanism the coupling strength between the gluons and the {{{s0}}} depends on its momentum. Therefore it is important to set the flag {{{fixed_couplings}}} to false in the {{{run_card.dat}}}. (See above for a sample {{{run_card.dat}}})
    30 
    31 The width is calculated automatically and is not read from the {{{param_card.dat}}} (this takes into account the values for {{{s0scalarf}}} and {{{s0axialf}}}).
     43These two values correspond to multiplication factors for the coupling strength, ''i.e.'', %$g_{s0tt}=$% {{{
     44s0scalarf
     45}}} %$i\frac{m_t}{v}+$% {{{
     46s0axialf
     47}}} $\frac{m_t}{v}\gamma_5$. Hence, the spin-0 can be a scalar or a pseudo-scalar or a mixed CP state by playing around with these two factors.
     48
     49Due to the loop in the production mechanism the coupling strength between the gluons and the {{{
     50s0
     51}}} depends on its momentum. Therefore it is important to set the flag {{{
     52fixed_couplings
     53}}} to false in the {{{
     54run_card.dat
     55}}}. (See above for a sample {{{
     56run_card.dat
     57}}})
     58
     59The width is calculated automatically and is not read from the {{{
     60param_card.dat
     61}}} (this takes into account the values for {{{
     62s0scalarf
     63}}} and {{{
     64s0axialf
     65}}}).
    3266
    3367=== spin-0, color octet ===
     
    3569([attachment:proc_card_o0.dat proc_card_o0.dat]: topBSM spin-0 color octet proc_card.dat)
    3670
    37 The spin-0, color octet particle, in the {{{topBSM}}} called {{{o0}}} (PDG code: 6000046), is a scalar, colored particle that couples only to top quarks. The production of the spin-0 is only through a top quark loop by gluon fusion. And its decay is directly to two top quarks with a branching ratio %$\textrm{BR}(s0\to t\bar{t})=1$%.
    38 
    39 It's coupling strength to the top quark is by default equal to the SM Higgs coupling to top quarks, ''i.e.'', %$im_t/v$%, but this can be changed in the {{{param_card.dat}}}. In the {{{param_card.dat}}} there are the following two lines:
     71The spin-0, color octet particle, in the {{{
     72topBSM
     73}}} called {{{
     74o0
     75}}} (PDG code: 6000046), is a scalar, colored particle that couples only to top quarks. The production of the spin-0 is only through a top quark loop by gluon fusion. And its decay is directly to two top quarks with a branching ratio $\textrm{BR}(s0\to t\bar{t})=1$.
     76
     77It's coupling strength to the top quark is by default equal to the SM Higgs coupling to top quarks, ''i.e.'', %$im_t/v$%, but this can be changed in the {{{
     78param_card.dat
     79}}}. In the {{{
     80param_card.dat
     81}}} there are the following two lines:
    4082{{{
    4183         3.     1.00000000e+00   # o0scalarf  ,spin-0 scalar mult.fac.
     
    4385}}}
    4486
    45 These two values correspond to multiplication factors for the coupling strength, ''i.e.'', %$g_{o0tt}=$% {{{o0scalarf}}} %$i\frac{m_t}{v}+$% {{{o0axialf}}} %$\frac{m_t}{v}\gamma_5$%. Hence, the spin-0 can be a scalar or a pseudo-scalar or a mixed CP state by playing around with these two factors.
    46 
    47 Due to the loop in the production mechanism the coupling strength between the gluons and the {{{o0}}} depends on its momentum. Therefore it is important to set the flag {{{fixed_couplings}}} to false in the {{{run_card.dat}}}. (See above for a sample {{{run_card.dat}}})
    48 
    49 The width is calculated automatically and is not read from the {{{param_card.dat}}} (this takes into account the values for {{{o0scalarf}}} and {{{o0axialf}}}).
     87These two values correspond to multiplication factors for the coupling strength, ''i.e.'', %$g_{o0tt}=$% {{{
     88o0scalarf
     89}}} %$i\frac{m_t}{v}+$% {{{
     90o0axialf
     91}}} $\frac{m_t}{v}\gamma_5$. Hence, the spin-0 can be a scalar or a pseudo-scalar or a mixed CP state by playing around with these two factors.
     92
     93Due to the loop in the production mechanism the coupling strength between the gluons and the {{{
     94o0
     95}}} depends on its momentum. Therefore it is important to set the flag {{{
     96fixed_couplings
     97}}} to false in the {{{
     98run_card.dat
     99}}}. (See above for a sample {{{
     100run_card.dat
     101}}})
     102
     103The width is calculated automatically and is not read from the {{{
     104param_card.dat
     105}}} (this takes into account the values for {{{
     106o0scalarf
     107}}} and {{{
     108o0axialf
     109}}}).
    50110
    51111=== spin-1, color singlet ===
     
    53113([attachment:proc_card_S1.dat proc_card_S1.dat]: topBSM spin-1 color singlet proc_card.dat)
    54114
    55 The spin-1, color singlet particle in the {{{topBSM}}} is called {{{s1}}} (PDG code: 6000047). This spin-1 particle is a similar to the SM Z boson. Its mass and width have to be set in the {{{param_card.dat}}}. By default it has the same couplings as the SM Z boson (only couplings to fermions are implemented). By changing the multiplication factors in the {{{BLOCK MGUSER}}} in the {{{param_card.dat}}} the coupling strengths can be altered.
     115The spin-1, color singlet particle in the {{{
     116topBSM
     117}}} is called {{{
     118s1
     119}}} (PDG code: 6000047). This spin-1 particle is a similar to the SM Z boson. Its mass and width have to be set in the {{{
     120param_card.dat
     121}}}. By default it has the same couplings as the SM Z boson (only couplings to fermions are implemented). By changing the multiplication factors in the {{{
     122BLOCK MGUSER
     123}}} in the {{{
     124param_card.dat
     125}}} the coupling strengths can be altered.
    56126
    57127=== spin-1, color octet ===
     
    59129([attachment:proc_card_O1.dat proc_card_O1.dat]: topBSM spin-1 color octet proc_card.dat)
    60130
    61 The spin-1, color octet particle in the {{{topBSM}}} is called {{{o1}}} (PDG code: 6000048). This spin-1 particle is a similar to a heavy gluon. Its mass and width have to be set in the {{{param_card.dat}}}. By default it has the same couplings as the gluon (only couplings to quarks are implemented). By changing the multiplication factors in the {{{BLOCK MGUSER}}} in the {{{param_card.dat}}} the coupling strengths can be altered.
     131The spin-1, color octet particle in the {{{
     132topBSM
     133}}} is called {{{
     134o1
     135}}} (PDG code: 6000048). This spin-1 particle is a similar to a heavy gluon. Its mass and width have to be set in the {{{
     136param_card.dat
     137}}}. By default it has the same couplings as the gluon (only couplings to quarks are implemented). By changing the multiplication factors in the {{{
     138BLOCK MGUSER
     139}}} in the {{{
     140param_card.dat
     141}}} the coupling strengths can be altered.
    62142
    63143=== spin-2, ADD model ===
     
    65145([attachment:proc_card_ADD.dat proc_card_ADD.dat]: topBSM spin-2 ADD proc_card.dat)
    66146
    67 The spin-2 graviton particle of the large extra dimensions model (ADD) is called {{{s2}}} in the {{{topBSM}}} (PDG code: 6000049). Due to the large extra dimensions, the KK gravitons are almost degenerate in mass. Therefore in this model there is not a single resonance, but a very large number that contribute only together significantly. Effectively the denominator of the graviton propagator is calcelled by the sum over all the KK states.
    68 
    69 There is a cut-off scale {{{mstring}}} that you have to specify in the {{{param_card.dat}}}, as well as the number of extra dimensions (so far only implemented for 3 extra dimensions). The mass of the {{{s2}}} should be set equal to the cut-off scale, while the width is not used at all. Note that this cut-off scale is parameter in the model, this is '''not''' a cut on the ttbar invariant mass, and there will be [http://www.essaybank.com/ essay writing] events produced above this cut-off scale.
    70 
    71 For this model it is important that the couplings are calculated on an event-by-event basis, hence one should set the flag {{{fixed_couplings}}} in the {{{run_card.dat}}} to false. (For an example {{{run_card.dat}}} see above.)
     147The spin-2 graviton particle of the large extra dimensions model (ADD) is called {{{
     148s2
     149}}} in the {{{
     150topBSM
     151}}} (PDG code: 6000049). Due to the large extra dimensions, the KK gravitons are almost degenerate in mass. Therefore in this model there is not a single resonance, but a very large number that contribute only together significantly. Effectively the denominator of the graviton propagator is calcelled by the sum over all the KK states.
     152
     153There is a cut-off scale {{{
     154mstring
     155}}} that you have to specify in the {{{
     156param_card.dat
     157}}}, as well as the number of extra dimensions (so far only implemented for 3 extra dimensions). The mass of the {{{
     158s2
     159}}} should be set equal to the cut-off scale, while the width is not used at all. Note that this cut-off scale is parameter in the model, this is '''not''' a cut on the ttbar invariant mass, and there will be [http://www.essaybank.com/ essay writing] events produced above this cut-off scale.
     160
     161For this model it is important that the couplings are calculated on an event-by-event basis, hence one should set the flag {{{
     162fixed_couplings
     163}}} in the {{{
     164run_card.dat
     165}}} to false. (For an example {{{
     166run_card.dat
     167}}} see above.)
    72168
    73169=== spin-2, RS model ===
     
    75171([attachment:proc_card_RS.dat proc_card_RS.dat]: topBSM spin-2 RS proc_card.dat)
    76172
    77 In the RS model there are a number of KK resonances with their mass ratio's given by the zeros of the BesselJ function. The mass of the first resonance has to be given in the {{{param_card}}}, the others are calculated by the MadGraph code. Also the widths are calculated internally. Furthermore the ratio of %$\kappa/\bar{M}_{\textrm{planck}}$% also has to be specified in the {{{BLOCK MGUSER}}} to specify the size of the coupling. Note that the RS gravitons are implemented to couple only to quarks and gluons, but in the calculation of the widths, couplings to all SM particles are taken into account.
    78 
    79 Only the first 10 resonances are implemented, called {{{g1}}}, {{{g2}}},..., {{{g0}}} (PDG codes: 6000050...6000059) so setting the mass of the first resonance small and using a large value for the coupling strength should be used with care, because effects from higher resonances start getting more important in this part of the parameter space.
     173In the RS model there are a number of KK resonances with their mass ratio's given by the zeros of the BesselJ function. The mass of the first resonance has to be given in the {{{
     174param_card
     175}}}, the others are calculated by the MadGraph code. Also the widths are calculated internally. Furthermore the ratio of %$\kappa/\bar{M}_{\textrm{planck}}$% also has to be specified in the {{{
     176BLOCK MGUSER
     177}}} to specify the size of the coupling. Note that the RS gravitons are implemented to couple only to quarks and gluons, but in the calculation of the widths, couplings to all SM particles are taken into account.
     178
     179Only the first 10 resonances are implemented, called {{{
     180g1
     181}}}, {{{
     182g2
     183}}},..., {{{
     184g0
     185}}} (PDG codes: 6000050...6000059) so setting the mass of the first resonance small and using a large value for the coupling strength should be used with care, because effects from higher resonances start getting more important in this part of the parameter space.
    80186
    81187-- Main.RikkertFrederix - 09 Dec 2008
     
    98204
    99205
     206