NON-SUSY SEARCHES at the TEVATRON 1 Search for Randall Sundrum Graviton the Standard Model (SM) Is a Very Successful Description

NON-SUSY SEARCHES AT THE TEVATRON

LIDIJA ZIVKOVIˇ C´ Columbia University, 538 West 120th Street, New York, NY 10027

We present results from several new searches for physics beyond the Standard Model using up to 5.4 fb−1 of data collected with CDF and DØ experiments at the Fermilab Tevatron.

1 Search for Randall Sundrum Graviton

The Standard Model (SM) is a very successful description of particle physics up to the weak scale. One of the remaining puzzles, known as gauge hierarchy, is the large disparity between 16 the Planck scale, MP l = 10 TeV and the weak scale of the order of 1 TeV. Solution was proposed by Randall and Sundrum (RS) 1 in which a fifth dimension with a warped spacetime metric exists, bounded by two three-dimensional branes, the SM brane and the Planck brane. We assumed the simplest RS model, in which the SM fields are localized on the SM brane and gravity originates on the Planck brane with the graviton wave function exponentially suppressed away from the brane along the extra dimension. In this model, TeV scales are naturally generated from −kπrc the Planck scale due√ to a geometrical exponential factor (the warp factor), Λπ = MP le , where MP l = MP l/ 8π is the reduced Planck scale, k and rc are the curvature scale and compactification radius of the extra dimension respectively. We searched with a DØ detector for the first Klauza Klein (KK) graviton in the simplest RS model, where graviton decays to a pair of electrons or photons in a 5.4 fb−1 of data 2. We select events with two electromagnetic clusters, each with transverse momentum pT > 25 GeV and we search for narrow mass resonance in dielectron or diphoton final state. Figure 1 shows dielectron (left) and diphoton (right) invariant mass for data (black points), total background (white area with a blue line), and graviton signals with masses 300, 450 and 600 GeV and k/MP l = 0.02. Since we did not observe any signal above SM prediction we set an upper limit on the production of KK gravitons times the branching fraction into the ee final state using a Poisson log-likelihood ratio (LLR) test. Figure 2 (left) shows the resulting limits for several values of k/MP l. Figure 2 (right) shows 95% C.L. upper limit on k/MP l versus graviton mass M1 compared with the expected limit and the previously published exclusion.

2 Heavy Gauge Bosons decaying to dileptons

Many models predict new heavy gauge boson that will decay into two leptons 3. The E6 Z0s 0 0 are examples of speciﬁc new particles decaying to a lepton-antilepton ﬁnal state. The Zψ, Zχ, 0 0 0 0 Zη, ZI , Zsec and ZN are chosen to test the E6 model. We searched for a heavy resonances that decay into two electrons with CDF detector 4 in a 2.5 fb−1, and with DØ detector 5 in −1 a 3.6 fb . We selected two isolated electrons with pT > 25 GeV at both experiments. The 104 105 Data Data Instrumental background 3 Instrumental background 4 10 10 Total background Total background 3 2 Signal: M =300,450,600 GeV, k/M =0.02 10 Signal: M =300,450,600 GeV, k/M =0.02 10 1 Pl 1 Pl 102 10 10 Dé, 5.4 fb-1 -1 1 1 Dé, 5.4 fb -1 -1 10

Number of events / 4 GeV 10 Number of events / 4 GeV (a) -2 (b) 10-2 10 -3 -3 10 200 400 600 800 1000 10 200 400 600 800 1000 Mee (GeV) M γγ (GeV)

Figure 1: Invariant mass of ee (left) and γγ (right).

Pl 0.1 95% CL upper limit M excluded at 95% CL 0.09 expected limit k/ expected limit expected limit ± 1σ

ee) (fb) 0.08 10 expected limit ± 2σ D0 PRL 100, 091802 (2008) → 0.07 k/Mpl=0.01 k/Mpl=0.02 0.06 B(G

× k/M =0.05 pl 0.05 k/M =0.10 pl 0.04

G+X) 1 0.03 -1 → p Dé, 5.4 fb-1 0.02 Dé, 5.4 fb (p

σ 0.01 200 300 400 500 600 700 800 900 1000 1100 0 300 400 500 600 700 800 900 1000 1100 Graviton Mass M1 (GeV) Graviton Mass M1 (GeV)

Figure 2: Upper limit on σ(pp¯ → G + X) × BR(G → ee) compared with the expected limit and the theoretical predictions for different couplingsk/M¯ P l (left) and an upper limit on k/M¯ P l versus graviton mass M1 (right). main irreducible background is Drell Yan production. Other backgrounds include instrumental backgrounds where one or both electrons were missidentified, and smaller SM processes. Figure 3 (left) shows the observed dielectron invariant mass spectrum from 2.5 fb−1 of data collected with CDF detector together with the expected backgrounds. The most significant region of excess of data over background occurs for a dielectron invariant mass window of 240 GeV, and is 3.8 standard deviations above the SM prediction. Figure 3 (right) shows the observed upper limits from data and the expected limits from background-only simulated events for spin 1 particles as a function of the e+e invariant mass, together with the expected cross sections for Z0. CDF Run II Preliminary CDF Run II Preliminary -1 ) 2 L = 2.5 fb 140 L = 2.5 fb-1 Cross Section Upper Limits (95% C.L., spin-1) 5 Observation ) 120 2

2 10 data 10 Expectation 100 104 Drell-Yan SM Z'

80 ) (fb)

- E Z' QCD 6 ψ Events/(10 GeV/c 60 e

+ E Z' 103 6 χ 40 Other SM e E6 Z'η 2 20 10 → E6 Z'I 160 180 200 220 240 260 280 300 320 340 E6 Z'sq M(ee) (GeV/c2) (Z'

10 Γ E6 Z'N × Events/(10 GeV/c 10

1 Z')

-1 →

10 p (p -2 10 σ

10-3

10-4 100 200 300 400 500 600 700 800 900 1000 1 200 300 400 500 600 700 800 900 1000 2 2 M(ee) (GeV/c ) MZ' (GeV/c )

Figure 3: Dielectron invariant mass (left) and an upper limit on cross section for various Z’ models.

Figure 4 (left) shows the observed dielectron invariant mass spectrum from 3.6 fb1 of data collected with DØ detector together with the expected backgrounds. At DØ we did not observe any excess in a mass region around 240 GeV, as shown in Figure 4 (middle). In the absence of any signiﬁcant signal, we set upper limits on the production cross section. Figure 4 (right) shows the expected and observed 95% conﬁdence-level upper limits on σ(pp¯ → Z0) × BR(Z0 → ee) for 0 0 ZSSM and E6 Z models as a function of Z mass. 5 10 -1 -1 D0 Run II Preliminary, 3.6fb data D0 Run II Preliminary, 3.6fb data 3 D0 Run II Preliminary, 3.6fb-1 Theory Z’ 10 SSM 4 Drell-Yan 70 Drell-Yan Theory Z’ 10 η Instrumental Instrumental Theory Z’ 3 Other SM Other SM ee) (fb) χ

10 60 → Theory Z’ψ Theory Z’ 2 sq 10 Theory Z’ Events/10 GeV 50 2 N Br(Z’ 10 × Theory Z’ 10 I Production σ × BR Z’) Events/10GeV 40 1 (95% CL - Observed) → p σ × 10-1 30 Production BR (p (95% CL - Expected) -2 σ 10 10 20 10-3 10 10-4 -5 0 1 10 200 400 600 800 1000 160 180 200 220 240 260 280 300 320 340 Mee(GeV) 400 500 600 700 800 900 1000 1100 Mee(GeV) Z’ Mass (GeV)

Figure 4: Dielectron invariant mass (left), also shown zoomed around 240 GeV (right), and an upper limit on cross section for various Z’ models..

3 Search for diboson resonances

Many extensions of the SM predict new heavy gauge boson that will decay into pair of SM gauge bosons. We searched for such resonances in electron, missing ET and two jets final state, with CDF detector 6 in 2.9 fb−1 of data. This final state has the advantage of searching for two types of diboson resonances, W ±W ∓ and W ±Z, with the same final state. We select events with an isolated electron with ET > 30 GeV, a missing ET > 30 GeV, 2 or 3 jets with ET > 30 GeV, and an overall HT > 150 GeV, where HT is defined as the sum of the electron ET , the missing ET and the jet ET of all jets with raw ET > 8 GeV. Since the real missing ET in the event is coming only from one neutrino fro the W decay, we used energy and momentum conservation to calculate EZ component, and thus to reconstruct the invariant mass of the resonance. We further optimized cuts on object pT to be greater than 40-120 depending on signal mass. Figure 5 shows invariant mass of WW(Z) system in a three scenarios that we investigated, W 0 (left), Z0 (middle) and RS graviton (right).

Figure 5: Diboson invariant mass for W 0 (left), Z0 (middle) and RS graviton (right).

In the absence of signal we set an upper limit on the cross section of the resonance decaying to two gauge bosons decaying further to electron, missing ET and two jets, where resonance is W 0 (see Figure 6 (left)), Z0 (see Figure 6 (middle)) and RS graviton (see Figure 6 (right))

Figure 6: An upper limit on cross section for heavy resonance, W 0 (left), Z0 (middle) and RS graviton (right) decaying to two bosons.

With DØ detector 7, we searched for a heavy charged boson decaying to WZ that further −1 decay to three leptons and missing ET in 4.1 fb of data. The events are required to have missing transverse energy greater than 30 GeV and at least three charged leptons with transverse momenta pT > 20 GeV satisfying the electron or muon identiﬁcation criteria. We require the presence of a candidate Z boson by selecting the electron pairs and muon pairs with opposite electric charges that have invariant mass nearest to the mass of the Z boson. Then, we select the highest transverse momentum lepton among the remaining lepton candidates in the event as the lepton from the W boson decay. The WZ transverse mass shown in Figure 7 (left) is used to discriminate between the W 0 signal and the backgrounds in the limit setting procedure. Since we did not observe any excess in a data over SM background we set upper limit on the σ×BR(W 0 → WZ) in Sequential Standard Model (see Figure 7). We also studied the sensitivity to other models that predict heavy charged boson. We interpreted the results in terms of the W 0WZ trilinear coupling normalized to the SSM value as function of the W 0 mass (see Figure 7).

-1 -1 5 D∅, 4.1 fb Data 103 D∅, 4.1 fb Expected 95% C.L. limit Excluded 95% C.L. region

WZ Monte Carlo Observed 95% C.L. limit 10 Expected 95% C.L. limit 4 WZ) (pb) γ 102 SSM value

Z+X (X= , jet, Z) → σ x B(W’→ WZ), SSM W’ 400 GeV SSM signal Events / 20 GeV 3 ±1 s.d. expected limit W’ 500 GeV SSM signal 10 x BR(W’

2 σ 1 1

1 -1

W’WZ coupling strength / SSM D∅, 4.1 fb 10-1 0 100 200 300 400 500 600 700 200 300 400 500 600 700 800 900 1000 200 300 400 500 600 700 800 900 1000 WZ transverse mass (GeV) MW’ (GeV) W’ mass (GeV)

Figure 7: Transverse mass of WZ system (left), an upper limit on cross section for W 0 in SSM (middle), and expected and excluded area of the W 0WZ coupling strength normalized to the SSM value as a function of the W 0 mass (right).

Acknowledgments

We thank the staﬀs at Fermilab and collaborating institutions, and acknowledge support from the DOE and NSF (USA); CEA and CNRS/IN2P3 (France); FASI, Rosatom and RFBR (Rus- sia); CNPq, FAPERJ, FAPESP and FUNDUNESP (Brazil); DAE and DST (India); Colciencias (Colombia); CONACyT (Mexico); KRF and KOSEF (Korea); CONICET and UBACyT (Ar- gentina); FOM (The Netherlands); STFC and the Royal Society (United Kingdom); MSMT and GACR (Czech Republic); CRC Program and NSERC (Canada); BMBF and DFG (Germany); SFI (Ireland); The Swedish Research Council (Sweden); and CAS and CNSF (China). I would also like to thank organizers of the Recontre de Moriond for ﬁnancial supportthat was provided for me. In addition, I would like to thank NSF and professors Chung-I Tan and Greg Landsberg for the grant that cover part of my costs.

References

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