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Search for the Limits on Anomalous Neutral Triple Gauge Couplings Via ZZ Production in the ``Νν Channel at FCC-Hh

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Search for the Limits on Anomalous Neutral Triple Gauge Couplings Via ZZ Production in the ``Νν Channel at FCC-Hh Search for the limits on anomalous neutral triple gauge couplings via ZZ production in the ``νν channel at FCC-hh A. Yilmaz∗ Department of Electrical and Electronics Engineering, Giresun University, 28200, Giresun, Turkey This paper presents the projections on the anomalous neutral triple gauge couplings (aNT GC) via pp ! ZZ production in the 2`2ν final state at a 100 TeV proton-proton collider, FCC-hh. The realistic FCC-hh detector environments and its effects taken into account in the analysis. The study is carried out in the mode where one Z boson decays into a pair of same-flavor, opposite-sign leptons (electrons or muons) and the other one decays to the two neutrinos. The new bounds on the charge-parity (CP)-conserving couplings C =Λ4 and CP-violating couplings C =Λ4, C =Λ4 BWe WW BW 4 and CBB =Λ achived at 95% Confidence Level (C.L.) using the transverse momentum of the dilepton `` system (pT ) are [− 0:042; + 0:042], [− 0:050; + 0:050], [− 0:050; + 0:050], and [− 0:048; + 0:048] in units of TeV−4, respectively. Keywords: FCC-hh, ZZ production, ``νν process, aNT GC I. INTRODUCTION be used at both tree level and loop level. In the frame- work of EFT theory, one can include the Anomalous Production of gauge boson pairs has an important role NTG vertices in an effective Lagrangian and it can be in the tests of the non-Abelian SU (2)L × U(1)Y gauge described by CP-conserving and CP-violating couplings, group of the electroweak sector of the Standard Model even though there is no electroweak NTGC exists at the (SM) and exploring the new physics at the TeV scale. tree level [3,4]. Additionaly, diboson production is also connected to the The dimension-eight (dim-8) effective Lagrangian for spontaneous breaking of the EW gauge symmetry [1,2]. nTGC in the EFT framework taking into account the For this reason, a signature of new physics beyond SM local U(1)EM and Lorentz symmetry can be given as [5] may reveal themselves via the possible deviation from SM expected values in neutral triple tuning (NTG) couplings (which includes ZZγ, Zγγ and ZZZ vertices). nT GC X Ci y New physics effects at high energy physics can be de- L = LSM + (Oi + Oi ) (1) Λ4 scribed in the terms of the Effective Field Theory (EFT) i parameters. This parameters is comprehensive to indi- cate the most likely places to observe these effects; be- where i is defined as an index of equations working sides they cover the gauge symmetries of the SM and can over the operators written as O y µρf ν g O y µρf ν g BWe = iH Beµν W Dρ;D H; BW = iH Bµν W Dρ;D H; y µρ ν y µρ ν OWW = iH Wµν W fDρ;D gH; OBB = iH Bµν B fDρ;D gH: (2) where Beµν is the dual B strength tensor. The layout given in the formula of the operators arXiv:2102.01989v1 [hep-ph] 3 Feb 2021 I I I J K Bµν = (@µBν − @ν Bµ);Wµν = σ (@µWν − @ν Wµ + gIJK Wµ Wν ) (3) I J IJ i i with hσ σ i = δ =2 and Dµ ≡ @µ − igwWµσ − ing from the interference between the SM and the dim-8 g0 operators when the new physics energy scale is high. i 2 BµY . It is expected that the main contribution of new The square of the amplitude with dim-8 operators does physics to the amplitude of ff ! ZZ process is com- not carry a significant contribution from the heavy new physics except that the interferences between the SM and the dim-8 and dimension-ten (dim-10) operators are ex- cessively suppressed. ∗ [email protected] The dim-6 operators can influence on nTGC at one- 2 loop level (at the order O(αs=^ 4πΛ2) despite being not into two same-flavor, oppositely charged leptons. This effective at the tree level [5]. Nevertheless, the tree process gives rise to the inclusion of a very low back- level contributions from dim-8 operators are of the or- ground, being kinematically reconstructable in the final der O(^sv2=Λ4). For this reason, a one-loop contribution state. In the ZZ ! ``νν channel, one of the Z decays of the dim-6 operators can be neglected in accordance into a same-flavor, oppositely-charged two leptons, while p with dim-8 operators considering Λ ∼< 2v π/α. the other one decays into neutrinos, which leads to an in- The coefficients of four dim-8 operators describing in crease in the missing transverse energy in the final state. 4 Eq.2 are the CP-conserving couplings CBWe =Λ and CP- The branching ratio of \``νν" final state is greater than 4 4 4 violating couplings CWW =Λ , CBW =Λ and CBB=Λ . the \4`" final state and the sensitivity to anomalous triple These are couplings of the dim-8 operators transformed gauge couplings (aTGCs) would be higher than the \4`" from the aTGC given in the Ref. [5] final state. \``νν" final state is still exposed to a larger The ``νν final state via the production of ZZ background contamination, and it requires strict experi- dibosons has been carried out at Fermilab (CDF) mental selection which leads to force one Z boson boosted collaboration [6,7] andpDØ collaborations [8]. Recently, against the other in the transverse plane is necessary the ATLAS [9] ( at s = 13 TeV, corresponding to to retain the background at a more feasible level [22]. an integrated luminosity of 36:1 fb−1) and CMS [10] Hence, the \``νν" final state includes more data quanti- experiments also reported the bounds on the EFT ties than the \4`" final state for the events with high-pT parameters using the ``νν final state. This high energy Z bosons, and this final state also presents competitive results in an improvement of the cross section, that precision for integrated and differential measurements, expands the scope of triple gauge coupling studies. as well as good sensitivity to aTGCs [23]. Therefore, Additionally numerous phenomenological studies have the ``νν final state is chosen to analyze using the FCC- been carried out the investigating the limits of aNTGCs hh option could be open a new possibility to extent the at hadron colliders in the EFT framework [11{17]. Ta- most stringent upper limits on EFT parameters thanks bleI summarise the latest experimental limits on dim-8 to its high center-of mass energy 100 TeV and capability p −1 couplings by LHC [18] ZZ ! 4l proceses at s = 13 to reach Lint = 30 ab (ultimately). −1 TeV with Lint = 137 fb and phenomenological limits This paper is arranged as follows: In Sect.II provides 4 4 4 details of the simulation environment for the ZZ diboson by Ref. [19] on CBWe =Λ , CWW =Λ , CBW =Λ and 4 CBB=Λ EFT parameters with the same final state using signal and background production samples at the FCC- −1 the 100 TeV FCC-hh option with Lint = 10 ab . In hh collider. Sect. III describes the algorithms developed this table, all couplings are set to zero except one that for event selection strategies of this phenomenological we are working on it. study in the ``νν final state. Obtained results for the ``νν final state analysis are given in Sect.IV. Finally, conclusions on the main results and findings of each cou- TABLE I. Current observed one dimensional 95% confidence plings are given in Sect.V. level (C.L.) bounds on the coefficients of dim-8 operators C =Λ4, C =Λ4, C =Λ4 and C =Λ4 by using the BWe WW BW BB transformation of the EFT parameters from Ref. [5] II. GENERATION OF SIGNAL AND Couplings Limit 95% C.L. BACKGROUND EVENTS (T eV −4) ZZ ! 4` [18] ZZ ! 4` [19] 4 CBW =Λ − 2:3; + 2:5 − 0:09; + 0:09 In this section, we present the production of the + − 4 pp ! ZZ ! ` ` νν¯ signal events as well as the back- CBB=Λ − 1:4; + 1:2 − 0:10; + 0:10 ground events (SM) taking into account the experimen- 4 − − CWW =Λ 1:4; + 1:3 0:21; + 0:21 tal conditions of FCC-hh. In order to find the bounds 4 − − CBWe =Λ 1:2; + 1:2 0:26; + 0:26 on the aNTG couplings, we used the UFO model file [24] implemented into Monte Carlo (MC) event generator For the future collider project, there are proposals for MadGraph5_aMC@NLO v2.6.4 [25]. The PYTHIA v8.2 [26] the future higher energy hadron colliders to carry out the package is utilized for the parton showering, fragmen- researches directly at the energy frontier. These propos- tation and hadronization of generated signal and back- als include FCC-ee, FCC-eh and FCC-hh collider types ground events. The LHAPDF v6.1.6 [27] library with working at different center of mass energies. The hadron NNPDF v2.3 [28, 29] set is a default set of parton distri- collider option of FCC (FCC-hh) is planned to run at the bution functions (PDFs) used to produce all MC sam- center of mass energy of 100 TeV and the integrated lumi- ples. The jets were collected by using FastJet [30] −1 −1 nosity of 1 ab (initial) and 30 ab (ultimate) [20, 21]. where the anti-kT algorithm [31] already implemented Searching the new physics effects in the production with a cone radius is R = 0.4. In the search of new of a diboson is requiring great effort.
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