Changes between Version 2 and Version 3 of TopBSM


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Timestamp:
04/13/12 08:55:09 (8 years ago)
Author:
md987
Comment:

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  • TopBSM

    v2 v3  
    33== Model for BSM physics studies in ttbar production ([http://arxiv.org/abs/0712.2355 arxiv:0712.2355]) Version 1.3 ==
    44
    5 The {{{
    6 topBSM
    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:
     5The
     6{{{
     7topBSM
     8}}}
     9is a model implemented to study BSM effects in the ttbar invariant mass spectrum. This model includes the following possible resonances in the ttbar spectrum:
    810   * spin-0, color singlet
    911   * spin-0, color octet
     
    1315   * spin-2, RS model
    1416
    15 Note that this {{{
    16 topBSM
    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 {{{
    18 param_card.dat
    19 }}} and {{{
    20 run_card.dat
    21 }}} that can be found [attachment:param_card.dat here] and [attachment:run_card.dat here].
     17Note that this
     18{{{
     19topBSM
     20}}}
     21model 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
     22{{{
     23param_card.dat
     24}}}
     25and
     26{{{
     27run_card.dat
     28}}}
     29that can be found [attachment:param_card.dat here] and [attachment:run_card.dat here].
    2230
    2331=== spin-0, color singlet ===
     
    2533([attachment:proc_card.dat proc_card.dat]: topBSM spin-0 color singlet proc_card.dat)
    2634
    27 The spin-0, color singlet particle, in the {{{
    28 topBSM
    29 }}} called {{{
     35The spin-0, color singlet particle, in the
     36{{{
     37topBSM
     38}}}
     39called
     40{{{
    3041s0
    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 
    33 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 {{{
    34 param_card.dat
    35 }}}. In the {{{
    36 param_card.dat
    37 }}} there are the following two lines:
     42}}}
     43(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 $\textrm{BR}(s0\to t\bar{t})=1$.
     44
     45It'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
     46{{{
     47param_card.dat
     48}}}
     49. In the
     50{{{
     51param_card.dat
     52}}}
     53there are the following two lines:
    3854{{{
    3955         1.     1.00000000e+00   # s0scalarf  ,spin-0 scalar mult.fac.
     
    4157}}}
    4258
    43 These two values correspond to multiplication factors for the coupling strength, ''i.e.'', %$g_{s0tt}=$% {{{
     59These two values correspond to multiplication factors for the coupling strength, ''i.e.'', $g_{s0tt}=$
     60{{{
    4461s0scalarf
    45 }}} %$i\frac{m_t}{v}+$% {{{
     62}}}
     63$i\frac{m_t}{v}+$
     64{{{
    4665s0axialf
    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 
    49 Due to the loop in the production mechanism the coupling strength between the gluons and the {{{
     66}}}
     67$\frac{m_t}{v}\gamma_5$. Hence, the spin-0 can be a scalar or a pseudo-scalar or a mixed CP state by playing around with these two factors.
     68
     69Due to the loop in the production mechanism the coupling strength between the gluons and the
     70{{{
    5071s0
    51 }}} depends on its momentum. Therefore it is important to set the flag {{{
     72}}}
     73depends on its momentum. Therefore it is important to set the flag
     74{{{
    5275fixed_couplings
    53 }}} to false in the {{{
    54 run_card.dat
    55 }}}. (See above for a sample {{{
    56 run_card.dat
    57 }}})
    58 
    59 The width is calculated automatically and is not read from the {{{
    60 param_card.dat
    61 }}} (this takes into account the values for {{{
     76}}}
     77to false in the
     78{{{
     79run_card.dat
     80}}}
     81. (See above for a sample
     82{{{
     83run_card.dat
     84}}}
     85)
     86
     87The width is calculated automatically and is not read from the
     88{{{
     89param_card.dat
     90}}}
     91(this takes into account the values for
     92{{{
    6293s0scalarf
    63 }}} and {{{
     94}}}
     95and
     96{{{
    6497s0axialf
    65 }}}).
     98}}}
     99).
    66100
    67101=== spin-0, color octet ===
     
    69103([attachment:proc_card_o0.dat proc_card_o0.dat]: topBSM spin-0 color octet proc_card.dat)
    70104
    71 The spin-0, color octet particle, in the {{{
    72 topBSM
    73 }}} called {{{
     105The spin-0, color octet particle, in the
     106{{{
     107topBSM
     108}}}
     109called
     110{{{
    74111o0
    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 
    77 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 {{{
    78 param_card.dat
    79 }}}. In the {{{
    80 param_card.dat
    81 }}} there are the following two lines:
     112}}}
     113(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 $\textrm{BR}(s0\to t\bar{t})=1$.
     114
     115It'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
     116{{{
     117param_card.dat
     118}}}
     119. In the
     120{{{
     121param_card.dat
     122}}}
     123there are the following two lines:
    82124{{{
    83125         3.     1.00000000e+00   # o0scalarf  ,spin-0 scalar mult.fac.
     
    85127}}}
    86128
    87 These two values correspond to multiplication factors for the coupling strength, ''i.e.'', %$g_{o0tt}=$% {{{
     129These two values correspond to multiplication factors for the coupling strength, ''i.e.'', $g_{o0tt}=$
     130{{{
    88131o0scalarf
    89 }}} %$i\frac{m_t}{v}+$% {{{
     132}}}
     133$i\frac{m_t}{v}+$
     134{{{
    90135o0axialf
    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 
    93 Due to the loop in the production mechanism the coupling strength between the gluons and the {{{
     136}}}
     137$\frac{m_t}{v}\gamma_5$. Hence, the spin-0 can be a scalar or a pseudo-scalar or a mixed CP state by playing around with these two factors.
     138
     139Due to the loop in the production mechanism the coupling strength between the gluons and the
     140{{{
    94141o0
    95 }}} depends on its momentum. Therefore it is important to set the flag {{{
     142}}}
     143depends on its momentum. Therefore it is important to set the flag
     144{{{
    96145fixed_couplings
    97 }}} to false in the {{{
    98 run_card.dat
    99 }}}. (See above for a sample {{{
    100 run_card.dat
    101 }}})
    102 
    103 The width is calculated automatically and is not read from the {{{
    104 param_card.dat
    105 }}} (this takes into account the values for {{{
     146}}}
     147to false in the
     148{{{
     149run_card.dat
     150}}}
     151. (See above for a sample
     152{{{
     153run_card.dat
     154}}}
     155)
     156
     157The width is calculated automatically and is not read from the
     158{{{
     159param_card.dat
     160}}}
     161(this takes into account the values for
     162{{{
    106163o0scalarf
    107 }}} and {{{
     164}}}
     165and
     166{{{
    108167o0axialf
    109 }}}).
     168}}}
     169).
    110170
    111171=== spin-1, color singlet ===
     
    113173([attachment:proc_card_S1.dat proc_card_S1.dat]: topBSM spin-1 color singlet proc_card.dat)
    114174
    115 The spin-1, color singlet particle in the {{{
    116 topBSM
    117 }}} is called {{{
     175The spin-1, color singlet particle in the
     176{{{
     177topBSM
     178}}}
     179is called
     180{{{
    118181s1
    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 {{{
    120 param_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 {{{
     182}}}
     183(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
     184{{{
     185param_card.dat
     186}}}
     187. 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
     188{{{
    122189BLOCK MGUSER
    123 }}} in the {{{
    124 param_card.dat
    125 }}} the coupling strengths can be altered.
     190}}}
     191in the
     192{{{
     193param_card.dat
     194}}}
     195the coupling strengths can be altered.
    126196
    127197=== spin-1, color octet ===
     
    129199([attachment:proc_card_O1.dat proc_card_O1.dat]: topBSM spin-1 color octet proc_card.dat)
    130200
    131 The spin-1, color octet particle in the {{{
    132 topBSM
    133 }}} is called {{{
     201The spin-1, color octet particle in the
     202{{{
     203topBSM
     204}}}
     205is called
     206{{{
    134207o1
    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 {{{
    136 param_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 {{{
     208}}}
     209(PDG code: 6000048). This spin-1 particle is a similar to a heavy gluon. Its mass and width have to be set in the
     210{{{
     211param_card.dat
     212}}}
     213. By default it has the same couplings as the gluon (only couplings to quarks are implemented). By changing the multiplication factors in the
     214{{{
    138215BLOCK MGUSER
    139 }}} in the {{{
    140 param_card.dat
    141 }}} the coupling strengths can be altered.
     216}}}
     217in the
     218{{{
     219param_card.dat
     220}}}
     221the coupling strengths can be altered.
    142222
    143223=== spin-2, ADD model ===
     
    145225([attachment:proc_card_ADD.dat proc_card_ADD.dat]: topBSM spin-2 ADD proc_card.dat)
    146226
    147 The spin-2 graviton particle of the large extra dimensions model (ADD) is called {{{
     227The spin-2 graviton particle of the large extra dimensions model (ADD) is called
     228{{{
    148229s2
    149 }}} in the {{{
    150 topBSM
    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 
    153 There is a cut-off scale {{{
     230}}}
     231in the
     232{{{
     233topBSM
     234}}}
     235(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.
     236
     237There is a cut-off scale
     238{{{
    154239mstring
    155 }}} that you have to specify in the {{{
    156 param_card.dat
    157 }}}, as well as the number of extra dimensions (so far only implemented for 3 extra dimensions). The mass of the {{{
     240}}}
     241that you have to specify in the
     242{{{
     243param_card.dat
     244}}}
     245, as well as the number of extra dimensions (so far only implemented for 3 extra dimensions). The mass of the
     246{{{
    158247s2
    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 
    161 For this model it is important that the couplings are calculated on an event-by-event basis, hence one should set the flag {{{
     248}}}
     249should 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.
     250
     251For this model it is important that the couplings are calculated on an event-by-event basis, hence one should set the flag
     252{{{
    162253fixed_couplings
    163 }}} in the {{{
    164 run_card.dat
    165 }}} to false. (For an example {{{
    166 run_card.dat
    167 }}} see above.)
     254}}}
     255in the
     256{{{
     257run_card.dat
     258}}}
     259to false. (For an example
     260{{{
     261run_card.dat
     262}}}
     263see above.)
    168264
    169265=== spin-2, RS model ===
     
    171267([attachment:proc_card_RS.dat proc_card_RS.dat]: topBSM spin-2 RS proc_card.dat)
    172268
    173 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 {{{
     269In 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
     270{{{
    174271param_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 {{{
     272}}}
     273, 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
     274{{{
    176275BLOCK 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 
    179 Only the first 10 resonances are implemented, called {{{
     276}}}
     277to 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.
     278
     279Only the first 10 resonances are implemented, called
     280{{{
    180281g1
    181 }}}, {{{
     282}}}
     283,
     284{{{
    182285g2
    183 }}},..., {{{
     286}}}
     287,...,
     288{{{
    184289g0
    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.
     290}}}
     291(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.
    186292
    187293-- Main.RikkertFrederix - 09 Dec 2008