Search for new physics in monojet events in pp collisions at sqrt(s) = 8 TeV

Abstract

A search has been made for events containing an energetic jet and an imbalance in transverse momentum using a data sample of pp collisions at a center-of-mass energy of 8 TeV. The data were collected by the CMS detector at the LHC and correspond to an integrated luminosity of 19.5fb^-1. The number of observed events is consistent with the standard model expectation. Constraints on the dark matter-nucleon scattering cross sections are determined for both spin-independent and spin-dependent interaction models. Limits are also placed on the Arkani-Hamed, Dimopoulos, and Dvali model parameter M_D determined as a function of the number of extra dimensions and the production of Unparticles. The Physics Analysis Summary is here: EXO-12-048 PAS

Approved Plots from EXO-12-048 PAS

Figure	Caption
	Transverse momentum distribution of the leading pT jet . The figure is shown with all analysis cuts applied. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, NJets ≤ 2 and ∆φ(j1, j2) < 2.5.
EPS PDF JPG
	Pseudorapidity distribution of the leading pT jet . The figure is shown with all analysis cuts applied. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, NJets ≤ 2 and ∆φ(j1, j2) < 2.5.
EPS PDF JPG
	The jet multiplicity distribution. The figure is shown with all analysis cuts applied, except jet multiplicity. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, and ∆φ(j1, j2) < 2.5.
EPS PDF JPG
	The ∆φ(j1, j2) distribution. The figure is shown with all analysis cuts applied except ∆φ(j1, j2). Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, and NJets ≤ 2.
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		Missing transverse momentum after all selection cuts for data and SM backgrounds. Representative signal points for dark matter, ADD and Unparticles are also overlaid. Events with Emiss > 1 TeV are included in the overflow bin.
EPS PDF JPG	EPS PDF JPG
	The dimuon invariant mass distribution is shown for data (black full points with error bars) and simulation (histogram) for 60 < Mμμ < 120 GeV/c2. The MC prediction has been normalized to the data yields. There is no significant non-Z background.
EPS PDF JPG
	The dimuon pT distribution is shown for data (black full points with error bars) and simulation (histogram) for 60 < Mμμ < 120 GeV/c2. The MC prediction has been normalized to the data yields. There is no significant non-Z background.
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	The transverse mass distribution MT in the single muon data control sample and predictions for W(μν), t ̄t, Z(μμ) and single-top production.
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	The W transverse momentum distribution in the single muon data control sample and predictions for W(μν), t ̄t, Z(μμ) and single-top production.
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	Comparison of lower limits on MD versus the number of extra dimensions with LEP, CDF, and D0.
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	Limits on the contact interaction scale Λ as a function of the DM mass for the the spin independent model of the current analysis using 19.5 fb−1 of 8 TeV data. Also shown is the result from the previous analysis using 5 fb−1 of 7 TeV data.
EPS PDF JPG
	Limits on the contact interaction scale Λ as a function of the DM mass for the the spin dependent model of the current analysis using 19.5 fb−1 of 8 TeV data. Also shown is the result from the previous analysis using 5 fb−1 of 7 TeV data.
EPS PDF JPG
		Comparison of CMS MonoJet 90% CL upper limits on the nucleon cross section versus dark matter mass for the spin independent model with CDF, XENON100, CoGeNT and CDMSII. (left) The original figure from the PAS. (right) An alternative figure used in CERN COURIER, May 22, 2013. For this plot, 68% and 90% contours are included for the candidate events from CDMS (arXiv:1304.4279 [hep-ex]).
EPS PDF JPG	EPS PDF JPG
	CMS MonoJet 90% CL upper limit on the nucleon cross section versus dark matter mass for the scalar operator model.
EPS PDF JPG
		Comparison of CMS MonoJet 90% CL upper limits on the nucleon cross section versus dark matter mass for the spin dependent model with CDF, SIMPLE, CDMSII, COUPP, Super-K, and IceCube. At left, the original figure from the PAS. On the right, an alternative figure used in CERN COURIER, May 22, 2013, which include the 68% and 90% contours for the candidate events from CDMS (arXiv:1304.4279 [hep-ex]).
EPS PDF JPG	EPS PDF JPG
	Observed limits on Λ as a function of the mass of the mediator (M), assuming vector interactions and a dark matter mass of 50 GeV (blue) and 500 GeV (red). The width of the mediator was varied between M/3, M/10 and M/8Pi.
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	95% CL upper limits on the unparticle production rate in pb compared to limits from previous CMS analyses.
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Supplementary Plots from EXO-12-048

Figure	Caption
	Transverse momentum distribution of the second leading pT jet . The figure is shown with all analysis cuts applied. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, NJets ≤ 2 and ∆φ(j1, j2) < 2.5.
EPS PDF JPG
	Pseudorapidity distribution of the second leading pT jet . The figure is shown with all analysis cuts applied. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, NJets ≤ 2 and ∆φ(j1, j2) < 2.5.
EPS PDF JPG
	The ∆φ(j1, j2) distribution. The figure is shown with all analysis cuts applied. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, NJets ≤ 2 and ∆φ(j1, j2) < 2.5.
EPS PDF JPG
	Jet multiplicity distribution. The figure is shown with all analysis cuts applied. Cuts include pT(j1) > 110GeV/c, pT(j2)>30GeV/c, abs(η(j1)) < 2.4, NJets ≤ 2 and ∆φ(j1, j2) < 2.5.
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	Comparison of lower limits on MD versus the number of extra dimensions with ATLAS, LEP, CDF, and D0.
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	Observed and expected 95% CLs limits on ADD versus theoretical cross section and as a function of MD. Limits are shown on dimension δ=3.
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	The observed (solid lines) and expected (dashed lines) 95% CLs limits on σ × A × ε on the possible contributions from new physics passing the selection requirements for the different signal regions.
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Event Displays from EXO-12-048

(click on the event display to get PNG)

Event Details	ρφ View	ρZ View	3D View
Run 204553 Event 26729384 Monojet candidate event
Run 204553 Event 36479045 W(mu+nu) + jets candidate event. The W(mu+nu) + jets events are used to predict the remaining W+jets background in monojet analysis.
Run 204564 Event 448966153 Z(mu+mu) + jets candidate event. The Z(mu+mu) + jets events are used to predict the invisible Z background in monojet analysis.

Standard Model MC samples

Process	x-sec (pb)	Details
DY + Jets, Pt(Z) > 100 GeV/c, leptonic decays	34.1	Z(l,l)+0,1,2,3,4 jets, Jet Pt min = 10 GeV, Pt(l,l) > 100 GeV/c, MLM matching with qcut = 10 GeV, xqcut = 20 GeV, cteq6l1
W + Jets (leptonic W decays)	67812	W(LNu)+0,1,2,3,4 jets, Jet Pt min = 10 GeV/c, MLM matching with qcut = 10 GeV, xqcut = 20 GeV, cteq6l1
t-tbar	225.2	t+tbar+0,1,2,3 jets, pt(t) > 20 GeV/c, pt(b)>20 GeV/c, MLM matching with qcut = 20 GeV, xqcut = 20 GeV, cteq6l1
Single t, s-channel	2.82
Single t, t-channel	47.0
Single t, tW-channel	10.7
Single tbar, s-channel	1.57
Single tbar, t-channel	25.0
Single tbar, tW-channel	10.7
QCD (pT-hat bin 300 - 470 GeV/c)	1759.55	MSEL = 1 (QCD hight pT processes), CKIN(3) = 300, CKIN(4) = 470, pythia6 tune Z2star
QCD (pT-hat bin 470 - 600 GeV/c)	113.88	MSEL = 1 (QCD hight pT processes), CKIN(3) = 470, CKIN(4) = 600, pythia6 tune Z2star
QCD (pT-hat bin 600 - 800 GeV/c)	27.0	MSEL = 1 (QCD hight pT processes), CKIN(3) = 600, CKIN(4) = 800, pythia6 tune Z2star
QCD (pT-hat bin 800 - 1000 GeV/c)	3.6	MSEL = 1 (QCD hight pT processes), CKIN(3) = 800, CKIN(4) = 1000, pythia6 tune Z2star
QCD (pT-hat bin 1000 - 1400 GeV/c)	0.74	MSEL = 1 (QCD hight pT processes), CKIN(3) = 1000, CKIN(4) = 1400, pythia6 tune Z2star
QCD (pT-hat bin 1400 - 1800 GeV/c)	0.034	MSEL = 1 (QCD hight pT processes), CKIN(3) = 1400, CKIN(4) = 1800, pythia6 tune Z2star
QCD (pT-hat bin 1800+ GeV/c)	0.0018	MSEL = 1 (QCD hight pT processes), CKIN(3) = 1800, pythia6 tune Z2star
Z(nu,nu) + Jets (HT bin 50 - 100 GeV/c)	381.2	Z(Nu,Nu)+0,1,2,3,4 jets, Jet Pt min = 10 GeV/c, 50 < HT < 100, MLM matching with qcut = 10 GeV, xqcut = 15 GeV, cteq6l1
Z(nu,nu) + Jets (HT bin 100 - 200 GeV/c)	160.3	Z(Nu,Nu)+0,1,2,3,4 jets, Jet Pt min = 10 GeV/c, 100 < HT < 200, MLM matching with qcut = 10 GeV, xqcut = 15 GeV, cteq6l1
Z(nu,nu) + Jets (HT bin 200 - 400 GeV/c)	41.5	Z(Nu,Nu)+0,1,2,3,4 jets, Jet Pt min = 10 GeV/c, 200 < HT < 400, MLM matching with qcut = 10 GeV, xqcut = 15 GeV, cteq6l1
Z(nu,nu) + Jets (HT bin 400+ GeV/c)	5.3	Z(Nu,Nu)+0,1,2,3,4 jets, Jet Pt min = 10 GeV/c, 400 < HT, MLM matching with qcut = 10 GeV, xqcut = 15 GeV, cteq6l1