Search for High Energy Electrons from New Neutral Massive Gauge Boson Decay in the CMS Detector at the LHC Using Monte Carlo Simulation

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1 Opn Journal o icrophysics, 013, 3, Publishd Onlin ay 013 ( Sarch or High Enrgy Elctrons rom Nw Nutral assiv Gaug Boson Dcay in th CS Dtctor at th LHC Using ont Carlo Simulation H... ansour, Nady Bakht Dpartmnt o Physics, Faculty o Scinc, Cairo Univrsity, Giza, Egypt mansourhsham@yahoo.com, nady.bakht@crn.ch, nady.bakht@yahoo.com Rcivd Dcmbr 7, 01; rvisd January 8, 013; accptd Fbruary 6, 013 Copyright 013 H... ansour, Nady Bakht. This is an opn accss articl distributd undr th Crativ Commons Attribution Licns, which prmits unrstrictd us, distribution, and rproduction in any mdium, providd th original work is proprly citd. ABSTRACT Th xistnc o nw havy nutral massiv boson Z is a atur o many xtnsions o Standard odl modls as th two-higgs-doublt modl (HD), th Hiddn Ablian Higgs odl (HAH), Lt-Right Symmtric odl (LRS), Squntial Standard odl (SS) and Baryon numbr minus Lpton numbr odl (B-L). In th prsnt work w sarch or two high nrgy lctrons producd rom dcaying L havy nutral massiv boson in th vnts producd in proton-proton collisions at LHC and can b dtctd by CS dtctor. W usd th data which is producd rom proton-proton collisions by ont Carlo vnts gnrator or dirnt nrgis at LHC, thn w us th angular distribution, invariant mass, combind transvrs momntum and combind rapidity distributions or th two high nrgy lctrons producd rom L dcay channl to dtct th L signal. B-L xtnsion o th S modl prdicts th xistnc o a L havy nutral massiv boson at high nrgis. From our rsults which w had simulatd using C programs or L in th B-L xtnsion o standard modl, w prdict a possibl xistnc o nw gaug Z B L at LHC in th mass rang 1 TV to 1.5 TV via lctrons idntiication o th two high nrgy lctrons by CS dtctor. Kywords: LHC; CS; ont Carlo Simulation; Nw Boson; S; B-L; Gaug Boson 1. Introduction Th Standard odl (S) o particls physics provids a good xplanation or most known particls but thr ar svral points nd an answr, dark mattr, dark nrgy, CP violation to xplain th baryonic mattr-antimattr asymmtry o th univrs and inally nutrino oscillations. From that w can say th S rquirs an xtnsion. B-L modl is an xtnsion or th S which is basd on th gaug group [1-3] GBL SU SU U U. Th in- C L Y B L varianc o th Lagrangian undr this gaug symmtry implis th xistnc o a nw gaug boson (byond th S ons) and th spontanous symmtry braking in this modl provids a natural xplanation or th prsnc o thr right-handd nutrinos in addition to an xtra gaug boson and a nw scalar Higgs. Thror, it can lad to a vry intrsting phnomnology which is dirnt rom th S rsults and it can b tstd at th LHC. An xtra nutral massiv gaug boson corrsponding to th B-L gaug symmtry is prdictd. Thr ar many modls which contain xtra gaug bosons. Ths modls can b classiid into two catgoris dpnding on whthr or not thy aris in a GUT scnario. In som o ths modls, Z and S Z ar not tru mass du to mixing. This mixing inducs th couplings btwn th xtra Z boson and th S rmions. In th B-L xtnsion o th S modl, th xtra Z B L boson and S rmions ar coupld through th nonvanishing B-L quantum numbrs. Sarching or L is accssibl via a clan dilpton signal at LHC. W will simulat B-L xtnsion o th S at LHC which is basd on th gaug group GBL SU3 SU U1 U1 using C C L Y programs thn sarch or th Z B L boson in th dilctron vnts producd in pp collisions at dirnt nrgis o LHC whr th lptonic dcay Z l l provids th most distinctiv signatur or obsrving th L signal at th Larg Hadron Collidr. Th rsults in this papr wr producd by using simulation vnts

2 H... ANSOUR, N. BAKHET 35 gnrator PYTHIA8 [4-6] and othr sotwar tools as CalcHp, adgraph/advnt, FynRuls, ROOT data analysis, Physics Analysis Workstation (PAW), ROOFIT packag to it any rsultd histogram in ordr to gt P.D.F. (Probability dnsity unction) and athmatica. In this papr, th rsults ar organizd into thr subsctions. Firstly, w prsnt th production o L at LHC which includs production cross sction, dirnt branching ratios and total width. Scondly, th dtction o Z B L signal at LHC via th dcay channl Z thn w study th dilctron angular distribution, dilctron asymmtry, Drll Yan background vnts or this channl and dilctron invariant mass. Thirdly, w prsnt th proprtis o L which includ Luminosity, Signiicanc, Transvrs momntum and Rapidity.. Rsults In this sction w prsnt our rsults or production and dtction o a Z B L signal o th B-L xtnsion o S using C programs [7,8]. W prsnt th production cross sction o Z BL at LHC as a unction o Z B L mass or various g valus (whr g is th U(1) B L gaug coupling constant) and or various nrgis at LHC, branching ratios as a unction o Z B L mass or havy nutrino mass = 00 GV which will act th rsults o Z B L du to th act that it is a havy particl. W obtaind dirnt rsults in comparison with R [9]. Th analysis in this papr did not tak into account th xistnc o nw dcay channl or havy nutrino in B-L modl which is on o th important signaturs o B-L modl and thy did not giv any branching ratio or havy nutrino. Atr that w will prsnt L total width as a unction o Z BL mass or various valus o g. Both angular distribution o dilctron and invariant mass o dilctron producd o Z B L dcay ar usd to dtct L signal at LHC. Finally, w will ocus on th proprtis o Z B L such as Luminosity, Signiicanc, Transvrs momntum and Rapidity..1. Production o L at LHC.1.1. Production Cross Sction In Figurs 1 and w prsnt th production cross sction or Z B L or th most rlvant production mchanisms or dirnt C nrgis. Figur 1 givs th cross sction or Z BL at LHC as a unction o L mass or various g valus (whr g is th U(1)B.L gaug coupling constant) at C nrgy o LHC = 14 TV. Figur givs cross sctions or Z B L at LHC or C nrgis s = 5, 7, 10, 1, 14 TV at ixd valu o g 0.. At th patron lvl, th L production cross sction dpnds on two main paramtrs, th mass o and th coupling constant g. Thror, th Z B L B-L modl is controlld by two paramtrs: th mass o th L and th coupling constant g dtrmining L couplings. Two xprimntal constraints xist on ths two paramtrs, th irst coms rom dirct sarch or havy nutral gaug bosons at th CDF xprimnt which xcluds a L mass lss than 600 GV and th scond limit coms rom LEP II whr: L 6 TV (1) g Th intractions o L boson with th S rmions in B-L modl is dscribd by L Y gz () Z int B L BL L as a unction o L Figur 1. Cross sction or mass or various g valus (whr gaug coupling constant) at ixd C nrgy o LHC = 14 TV. g is th U(1) B L Figur. Cross sction or L as a unction o L mass or various nrgis o LHC at s = 5, 7, 10, 1, 14 TV at ixd valu o g 0..

3 36 H... ANSOUR, N. BAKHET whr Y B L is th B-L charg associatd with th rmions (s Tabl 1). Th xtra nutral gaug boson Z B L acquirs a mass du to th B-L gaug symmtry braking L 4gv (3) whr g is th U(1) B L gaug coupling constant and υ is th symmtry braking scal. Th production cross sctions or L signal in Figurs 1 and wr computd using adgraph5 and PYTHIA8 whr w gnratd th procss pp L o B-L modl using adgraph5 and xport this procss to PHYTHIA8 thn th main switchs ar on or Initial stat Radiation(ISR), Final Stat Radiation(FSR), FSRin- Rsonancs, Dcay hadronization, allow rsonanc dcays and mastr switch or multiparton intractions to stay on..1.. Branching Ratios o L In Figur 3, th branching ratios o Z B L to dirnt quarks ar qual approximatly and or dirnt lptons ar highr than thos or quarks. Also th branching ratio or havy nutrino which hav mass 00 GV in our sarch is lss than thos or th chargd lptons and light nutrinos. In particular, BR Z B L ll varis btwn 17% to 17.5% whr (l = lctron, muon, tau) but or havy nutrino BR Z B L hh v v ) varis rom 6% to 8% and or light nutrino BR L vv varis BR Z qq varis rom btwn 8.5% to 9% and B L Tabl 1. B-L quantum numbr or dirnt particls. Particl L R v R q Y B-L /3 5.5% to 6%. Th probabilitis that Z B L can dcay into on light and on havy nutrino ar highly supprssd by th corrsponding (havy-light) nutrino mixing and thus thy can saly b nglctd. Havy nutrino is th most charactristic or B-L modl so it has an ct on dirnt branching ratios bcaus it is rathr massiv than th S nutrino. From Figur 3 on can sarch or L at LHC via a clan dilpton signal which can b on o th irst nw physics signaturs to b obsrvd at th LHC. W will study L in this papr by using th dcay channl o L to lctrons pair using PY- THIA8 and turn o all othr dcay channls or Z B L whr th ratio o dilctron channl is th highst on. Z.1.3. Total Width o B L L boson dcays only to rmions at tr-lvl and its width is givn by th ollowing xprssion Z BL Z 1π C v m 1 1 4m ZB L ZB L whr m is th mass and C th numbr o colors or th rmion typ. In Figur 4 w prsnt th total dcay width o th L as a unction o L mass or ixd valus o g. Figur 5 prsnts th total dcay width o th L as a unction o g or ixd valus o L mass. From Figurs 4 and 5 w not that th total width o a L gaug boson varis rom a w hundrds o GV ovr a mass rang o 0.5 Z B L 5 TV dpnding on th valu o g. Th dcay widths o L in this modl ar thn givn by: l gy BL (4) Z BL l l mzb L 4π (5) Figur 3. Branching ratios or or 00 GV. L h v L as a unction o Figur 4. Total width or or ixd valus o g. as a unction o mass Z B L ZB L

4 H... ANSOUR, N. BAKHET 37 Figur 5. Total width or ixd valus o L mass. L as a unction o g or q gy BL Z BL qq mz 8π s 1, q b, c s π, (6) t gy BL Z BL tt mz 8π 1 m t s smt O Z π m B L ZB L m Th main switchs or Initial Stat Radiation, Final Sat Radiation and multipl intractions ar on. Figur 4 prsnts th total width or L as a unction o mass L or ixd valus o g. Hr, w usd C nrgy o LHC 14 V. Figu r 5 prsnts th total width or L as a unction o g or ixd valus o Z B L mas s. W not that th total width o L inc ras with incrasing th mass o L. In Figur 6 w prsnt th rlativ variation o th total width as a unction o th havy nutrino mass or dirnt valus o L and or g 0.3. W not th importanc o taking into considration th havy nutrino sinc thir rlativ contribution to th total width can b as larg as 0% whr ZB is th total L width o L which includs all dcay channls (also dcay channl o havy nutrino ) whras ZB h L v dcoupld includs all dcay channls xcpt dcay chan- nl o havy nutrino is turn o. (7) sis, it has bn shown that th angular distribution o th dilpton vnts [10] can also b usd to tst th prsnc o a L boson by dtcting its intrrnc with th S Z boson. Th massiv rsonanc sarch tchniqu ( analysis) is xtndd to includ dilpton angular inormation to dtct, so w will us th dilctron angular distribution cos(θ * ) whr θ * is th angl in th dilctron rst rrnc ram btwn th ngativ lctron and th incidnt incoming quark. PY- THIA8 givs θ only in Lab ram but w us θ * hr which is in rst ram so w must convrt rom lab ram to rst ram to gt θ * by using boost vctor. W din two additional rrnc rams: a) th colliding proton C ram dnotd by O (this ram is idntical to th laboratory ram) and b) Th rst ram o th dilpton systm dnotd by O *. Th dilpton systm is boostd along th bam axis. Th z-axis is chosn as th dirction o on o th bams, and it is thn idntical or O and O * rams. It should b notd that thr is a sign ambiguity in th masurmnt o cos(θ * ) sinc or a particular vnt, thr is no inormation about whthr th incoming quark coms rom th positiv or ngativ z dirctions [11]. Instad, it is usul to considr th quantity cos, whr is th angl btwn th dilpton systm boost (rlativ to th O ram) and th lpton dirction Pl cos (8) Pl whr th boost vctor is Pl P l (9) El E l In ordr to obtain P l th boost vctor o th dilpton systm should b ound and th transormation to th O * ram should b prormd. Figur 7 givs th angular.. Dtction o ZB L Signal at LHC..1. Dilctron An gular Distribution In addition to th dilpton invariant mass analy- Figur 6. Total width or trino mass or ixd valus o ZB L as a unction o havy nu- Z and g 0.3.

5 38 H... ANSOUR, N. BAKHET Figur 7. Angular distribution o dilctron o ZB L boson dcay whr orward lctrons hav cos(θ * ) > 0 and backward lctrons hav cos(θ * ) < 0. distribution o dilctron o unction o cos(θ * ). L boson dcay as a... Dilctron Asymmtry A FB In th procss qq Z BL ll whr Z B L boson has both vctor and axial vctor couplings to th rmions, ths couplings crat an asymmtry in th momntum o th lctron visibl in th polar angl o th lpton pair's cntr o mass ram. This polar angl which is masurd in th cntr o mass ram o th lptons is typically rrrd to as th Collins Sopr ram. Th angular cross sction masurd in this ram is givn by: d qq ZBL ll A dcos 1 cos B cos (10) Hr θ * is th mission angl o th lctron rlativ to th quark momntum in th lpton s cntr o mass ram (s Figur 8). Th constants A and B ar dtrmind by th wak isospin and charg o th incidnt quarks as wll as th mass o th dilpton pair. From this cross sction, it is convnint to din N as th numbr o vnts whos θ * is positiv, and N b as th numbr o vnts whos θ * is ngativ. Th asymmtry can thn b writtn as: d d dcos 0 dcos 0 AFB d d (11) dcos 0 dcos 0 3 B N Nb 8 A N N b This is th gnral orm o th asymmtry. Collins and Sopr notd that an ambiguity xists in th dtrmination o th mission angl θ * whn considring Figur 8. Th lpton s cntr o mass ram and th Collins- Sopr ram. qq ll This Drll-Yan procss is quit simpl [1] whn th incoming quarks hav no transvrs momntum. In such a cas, th mission angl is dtrmind by th angl th lctron maks with th proton bam and thus th incoming quark momntum vctor. Howvr, sinc circular acclration implis a crtain amount o transvrs momntum by construction, an ambiguity ariss. Sinc th quark s individual momnta cannot b masurd, th momnta boostd into th cntr o mass ram o th lptons ar vn mor diicult to sparat. Consquntly, th dpndnc o th transvrs momntum must b minimizd. Th polar θ * axis is th bisctor o th proton bam momntum and th ngativ ( ) o th antiproton bam momntum whn th two ar boostd into th cntr o mass ram o th lptons. In so doing, th dpndnc on th transvrs momntum o th incoming quark pair is minimizd. Tabl shows th numbrs o orward and backward lctrons producd rom L dcay in th rang o L mass 500 GV to 1500 GV and also asymmtry calculation. Figur 9 shows th dilctron asymmtry distribution or orward and backward lctrons or various valus o masss. ZB L..3. Drll Yan Background Evnts Th histogram in Figur 10 shows th gnratd dilctron vnts or a rconstructd mass o 50 to 700 GV or S Z o. Thr is a pak cntrd on th 100 GV or 6000 vnts wr gnratd by PHYTHIA8. This pak, or rsonant signal corrsponds to th production o a Z o with a mass o GV. This procss is calld th Drll-Yan spctrum and dilctron ar producd rom Z o dcay and thy act as S background or Z procss BL o qq Z

6 H... ANSOUR, N. BAKHET 39 Tabl. Th numbrs o orward and backward lctrons producd rom ZB L dcay in th rang o L mass 500 GV to 1500 GV and also asymmt ry calculation. L mass (GV) Forward Elctrons N F cos(θ * ) > Backward Elctrons N B cos(θ * ) < Asymmtry A FB Figur 9. Dilctron asymmtry distribution or orward and backward lctrons or various valus o L masss. dilctron. Th rconstructd mass o Z o will b calculatd according to th quation: E E P P (1) z..4. Dilctron Invariant ass Now, w will us th dilpton invariant mass rom th dilpton vnts [13] to tst th prsnc o a Z B L boson at LHC through th massiv rsonanc sarch tchniqu ( analysis) bsid th last m thod o dilpton angular inormation to dtct Z BL which w hav usd bor. By using PYTHIA8, ROOT and ROOFIT w cratd a sris o L signals with masss rom 500 GV/c to 1500 GV/c as in Tabl 3, thn th mass o L is rconstructd rom th nrgy and momnta o th slctd dilctron at coupling constant qual g 0.1 [14]. W gnratd 5000 vnts or vry signal mass whr th backgrounds Drll-Yan vnts and dsird signal vnts ar slctd by applying a numbr o s lction cuts on all vnts sampls (5000 vnts). 1) Transvrs nrgy o slctd lctrons E T > 100 GV. ) Th slctd lctrons must b in th cntral or in th orward rgions o η < 1.44 or < η <.5 thn w choos th two highst-nrgy lctrons whr η is th psudo rapidity o mittd lctrons which dscribs th angl o a particl rlativ to bam axis. ln (13) θ is th angl btwn th particl momntum vctor P and th bam axis (Figur 11). From Figur 1 w ind a pak at 1 TV which is th rconstruction mass o L rom th lctron-positron invariant masss. This allowd us to compar th signal Tabl 3. Th xpctd numbr o vnts, signal vnts or ZB L, background vnts, and Signiicanc calculation at g 0.1 using PYTHIA8. Figur 10. Th Drll-Yan background lctrons producd rom Z o boson or quark and antiquark annihilation. Hr q is a quark rom an incoming proton and it is annihilatd with its antiparticl q rom anothr incoming o proton and producs a Z which thn dcays into two Z B L mass (GV) Expctd vnts N xp ass window (GV) Signal Background Signiicanc vnts N S vnts N B S

7 40 H... ANSOUR, N. BAKHET Figur 11. Th Ps udo rapidity o producd l ctrons o Z dcay. pak th mass windows is 450 GV thn σ = 75 and µ = W will intgrat th Gaussian rom 550 to 1450 to gt th raction o signal vnt, thn w will multiply this raction by th total xpctd vnts N xp to gt th numbr o signal vnt N S thn w can calculat th background vnts N B by: NB Nxp N S (14) Th signiicanc ormula is: NS S NS NBln1 NS (15) NB whr N S is th numbr o signal vnts and N B is th numbr o background vnts. Tabl 3 shows a summary o signal vnts and background vnts or dirnt valus o L mass and th corrsponding signiicanc. Figur 14 shows th signal signiicanc as a unction o th mass o or g 0.. ZB L Figur 1. Th rconstruction or ducd dilctron invariant masss at L mass rom pro- Z mass 1 TV. gnratd vnts with th Drll Yan background rom Figur Proprtis o L.3.1. Luminosity For ach gnratd signal, PYTHIA8 calculatd th cross sction or ach procss. This is important bcaus it allows us to scal our gnratd vnts to what an actual signal would look lik givn th luminosity [15]. Th luminosity is th numbr o vnts collision pr unit ara in an acclrator. Thror, th numbr o xpctd vnts N xp can b dtrmind by th ormula: N xp = L σ whr N xp = N S + N B and σ is th PYTHIA8 cross sction o gnratd vnts and L is th luminosity and N S is th numbr o signal vnts and N B is th numbr o background vnts. Figur 13 giv th rquird luminosity or L obsrvation at LHC or dirnt masss at Z B L. W not that th valu o th luminosity incrass by incrasing mass. Z B L.3.. Signiicanc Calculations To calculat th signiicanc, ach rconstructd mass is ittd by a Gaussian using th ROOFIT packag and using th standard dviation with 3σ mass window around th ittd pak or xampl rom Figur 1 at 1000 GV Figur 13. Luminosity rquird or obsrvation ZB L as a unction o L mass or g 0. at th C nrgy o LHC s = 14 TV. Figur 14. Signal signiicanc as a unction o th mass or or g 0.. ZB L

8 H... ANSOUR, N. BAKHET Transvrs omntum Figur 15 show th transvrs momntum P T distributions o positron and lctron pairs in invariant mass rgion GV producd rom Z B L dcay. Th rsults ar obtaind using PYTHIA8 o proton-proton collisions at a cntr-o-mass nrgy o 14 TV at L HC and g 0.. Th distributions ar masurd ovr th rangs η < 1.44 or < η <. 5 and th transvrs nrgy o slctd lctrons is E T > 100 GV. Th distributions or y and P T ar normalizd by total cross sctions within accptanc rgions dscribd ar shown in Figurs 16 and 17. Figurs 18 and 19 show th masurmnt o th rapidity y whr th transvrs-momntum P T distributions and rapidity o th L boson provid a nw inorma- tion about th dynamics o proton collisions at high nrgis and th P T spctrum provids a bttr undrstand- Figur 17. Th normalizd dirntial cross sction or Z boson as a unction o transvrs-momntum o di- lctron. Figur 15. Transvrs momntum or dilctron or mass o Z 1TV and nrgy o LHC = 14 TV and g 0.. Figur 18. Absolut valu o rapidity or dilctron or mass o Z and nrgy o LHC=14 TV and g 1TV 0.. Figur 16. Di rntial cross sction as a unction o dilc- tron transvrs momntum at g 0. and nrgy o LHC = 14 TV. Figur 19. Th normalizd dirntial cross sction or ZB L as a unction o th absolut valu o rapidity o dilctron or mass o Z BL 1TV at C nrgy o LHC = 14 T V and g 0..

9 4 H... ANSOUR, N. BAKHET ing o th undrlying collision procss at low transvrs momntum. Th masurmnts o th rapidity and transvrs momntum spctra ar basd on sampls ovr boson vnts rconstructd in ach dilpton dcay mod and collctd using high P T singl lpton. For th Z B L boson candidats slctd pairs o lptons ar rquird to hav a rconstructd invariant mass in th rang GV. Th two lctrons candidats with th highst P T in th vnt ar usd to rconstruct a Z B L candidat. Elctrons ar rquird to hav E T >100 GV and η < 1.44 or < η < Rapidity o Z B.L Th rapidity is dind as y 1 ln E PT E P T (16) whr E is th nr gy o th Z B L candidat and P T is its longitudinal momntum along th anticlockwis bam axis (th z axis o th dtct or). Th y and P T o Z B L ar dtrmind rom th lptons momnta. Th masurd dirntial dilctron cross sctions ar normalizd to th inclusiv Z cross sction. Th dirntial cross sction is dtrmind in ach y or bin by subtracting rom th numbr o dtctd vnts in a bin th stimatd numbr o background vnts. Th distributions ar corrctd or signal accptanc and icincy and or th cts o dtctor rsolution and lctromagntic inalstat radiation (FSR) using an unolding tchniqu basd on th invrsion o a rspons matrix. Th inal rsult taks into account th bin width and is normalizd by th masurd total cross sction. Th distribution o Z B L bosons is symmtric about y = 0 and thror th appropriat masurmnt is th distribution as a unction o th absolut valu o rapidity Th masurmnt is normalizd to th total cross sctio 1 d (17) d y and σ is th total cross sction is dtrmind by 70 vnts 3. Conclusion In this work, w hav prsntd th LHC potntial to discovr a havy nutral massiv gaug boson L in B-L xtnsion o S modl via sarch or two high nrgy lctrons using C programs whr w hav simulatd th production o L or dirnt cntr o mass nrgis at LHC or various valus o coupling constant g and also prsntd all possibl branching ratios o Z to dirnt dcay channls to rmions BL and prsntd th total width o Z B L. W hav usd th two high nrgy lctrons angular distribution and th two high nrgy lctrons invariant mass to dtct Z B L signal at LHC. Finally, w calculatd th luminosity, signiicanc, dilctron transvrs momntum, rapidity and dirntial cross sction. All ths signaturs prdict th xistnc o a nw gaug boson L at LHC in th mass rang 1 TV to 1.5 TV via dtction o th two high nrgy lctrons in CS. 4. Acknowldgmnts It is a plasur to thank L. Basso (Friburg Un iv. Grmany) or usul discussions o B-L modl, T. Sjostrand (Lund Univ. Swdn) or usul discussions o PYTHIA, J. Alwall (Stanord Univ. USA) or usul discussions o ad-graph5/adevnt and C. Duhr also many thanks to th administration o th aculty o scinc Cairo Univrsity Egypt particular to Pro. Gamal Abd El Nasir, Pro. Shri ourad and Pro. Omar Osman. REFERENCES [1] L. Basso, Ph.D. Thsis, Univrsity o Southampton, Southampton, 011. [] L. Basso, astr s Thsis, Univrsit y o Padua, Padova, 007. [3] L. Basso, A. Blyav and S. ortti, arxiv: v1 [hp-ph] Dc 008. [4] T. Sjostrand, S. rnna and P. Skands, PYTHIA 6.4 Physics and anual, Journ al o High Enrgy Physics, Vol. 6, 006. doi: / /006/05/06 [5] T. Sjostrand, CERN-LCGAPP July 005. [6] T. Sjostrand. [7] T. Sjostrand, P. Edn and C. Fribrg, Phys. Commun., 135, 38. [8] T. Sjostrand, t al., High-Enrgy-Physics Evnt Gnration with Pythia 6.1, Computr Physics Communications, Vol. 135, No., 001, pp doi: /s (00) [9] P in, Emam 008 J. Phys. G: Nucl. Part. Phys [10] CDF, Collaboration-arXiv:hp-x/060045v1, 006. [11] G. Blla, E. Etzion and N. Hod, Introduction to th CntOSES Projct and Havy Gaug Bosons Sarch at th LHC, arxiv: v1 [hp-x], pd [1] D. Bandurin, CS AN-008/044, Kansas Stat Univrsity, anhattan, 008. [13] D. Evans, C. Hill, J. Jackson and D. Nwbold, CS AN-008/048. [14]. Carna and A. Dalo, arxiv:hp-ph/ v1, 004. [15] Christophr Rogan Fall 004 Junior Papr.