Testing the technicolor interpretation of the CDF dijet excess at the 8-TeV LHC

Under the assumption that the dijet excess seen by the CDF Collaboration near 150 GeV in $Wjj$ production is due to the lightest technipion of the low-scale technicolor (LSTC) process ${\rho }_T\to W{\pi }_T$, we study its observability in LHC detectors for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. We describe interesting new kinematic tests that can provide independent confirmation of this LSTC hypothesis. We show that cuts similar to those employed by CDF, and recently by ATLAS, cannot confirm the dijet signal. We propose cuts tailored to the LSTC hypothesis and its backgrounds at the LHC that may reveal ${\rho }_T\to \ell \nu jj$. Observation of the isospin-related channel ${\rho }_T^{\pm }\to Z{\pi }_T^{\pm }\to {\ell }^{+}{\ell }^{-}jj$ and of ${\rho }_T^{\pm }\to WZ$ in the ${\ell }^{+}{\ell }^{-}{\ell }^{\pm }{\nu }_{\ell }$ and ${\ell }^{+}{\ell }^{-}jj$ modes will be important confirmations of the LSTC interpretation of the CDF signal. The $Z{\pi }_T$ channel is experimentally cleaner than $W{\pi }_T$ and its rate is known from $W{\pi }_T$ by phase space. It can be discovered or excluded with the collider data expected by the end of 2012. The $WZ\to 3\ell \nu$ channel is cleanest of all and its rate is determined from $W{\pi }_T$ and the LSTC parameter $\sin \chi$. This channel and $WZ\to {\ell }^{+}{\ell }^{-}jj$ are discussed as a function of $\sin \chi$.

Figure 1

CDF $M_{Wjj}$ distributions for $\int \mathcal{L}dt=7.3{\mathrm{fb}}^{-1}$ from the dijet signal region $115<M_{jj}<175\mathrm{GeV}$ [2]. Left: Expected backgrounds and data; right: background-subtracted data.

Figure 2

CDF $p_T(jj)$ distributions for $\int \mathcal{L}dt=7.3{\mathrm{fb}}^{-1}$ from the dijet signal region $115<M_{jj}<175\mathrm{GeV}$ [2]. Left: Expected backgrounds and data; right: background-subtracted data.

Figure 3

CDF $\Delta \varphi$ distributions for $\int \mathcal{L}dt=7.3{\mathrm{fb}}^{-1}$ from the dijet signal region $115<M_{jj}<175\mathrm{GeV}$ [2]. Left: Expected backgrounds and data; right: background-subtracted data.

Figure 4

CDF $\Delta R$ distributions for $\int \mathcal{L}dt=7.3{\mathrm{fb}}^{-1}$ from the dijet signal region $115<M_{jj}<175\mathrm{GeV}$ [2]. Left: Expected backgrounds and data; right: background-subtracted data.

Figure 5

The area-normalized $\Delta \chi$ and $\Delta R$ distributions for the primary parton/jet in ${\rho }_T$, $a_T\to W{\pi }_T$ production followed by ${\pi }_T\to \overline{q}q$ decay, constructed as described in the text. Red: pure distribution of primary parton before any radiation; blue: the distribution for the jets reconstructed as described in Sec. 3.

Figure 6

Left: The ATLAS $M_{jj}$ distribution for exactly two jets in $Wjj$ production at $\sqrt{s}=7\mathrm{TeV}$ and $\int \mathcal{L}dt=1.02{\mathrm{fb}}^{-1}$ (from Ref. 36). Right: Simulation of the $M_{jj}$ distribution in $Wjj$ production with ATLAS cuts [except that $p_T(\ell )>30\mathrm{GeV}$] for $1.0{\mathrm{fb}}^{-1}$. The open red histogram is the ${\pi }_T\to jj$ signal times 10.

Figure 7

The CMS $M_{jj}$ distributions for $4.7{\mathrm{fb}}^{-1}$ of $W\to \mu \nu$, $e\nu$ plus two or three jets data at $\sqrt{s}=7\mathrm{TeV}$ before (top left) and after (top right) the background subtraction summarized in the text (from Refs. 43, 44). On the bottom is our $M_{jj}$ distribution for the ${\rho }_T$, $a_T\to W{\pi }_T\to \ell {\nu }_{\ell }jj$ signal and backgrounds at the LHC for $5{\mathrm{fb}}^{-1}$. Augmented ATLAS-like cuts as described in the text were used. The open red histograms are the ${\pi }_T$ and ${\rho }_T$ signals times 10.

Figure 8

The $M_{jj}$ and $M_{Wjj}$ distributions of ${\rho }_T$, $a_T\to W{\pi }_T\to \ell {\nu }_{\ell }jj$ and backgrounds at the LHC for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. Augmented ATLAS-like cuts as described in the text are employed. The open red histograms are the unscaled ${\pi }_T$ and ${\rho }_T$ signals.

Figure 9

The $M_{jj}$ and $M_{Zjj}$ distributions of ${\rho }_T^{\pm }\to Z{\pi }_T^{\pm }\to {\ell }^{+}{\ell }^{-}jj$ and backgrounds at the LHC for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. The cuts used are described in the text. The open red histograms are the ${\pi }_T$ and ${\rho }_T$ signals.

Figure 10

The $\Delta R$ and $\Delta \chi$ distributions for ${\rho }_T^{\pm }\to Z{\pi }_T^{\pm }\to {\ell }^{+}{\ell }^{-}jj$ and backgrounds at the LHC for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. The cuts used are described in the text. The open red histograms are the signals.

Figure 11

Left: CMS $WZ\to 3\ell \nu$ cross section limits for $\int \mathcal{L}dt=4.98{\mathrm{fb}}^{-1}$ at $\sqrt{s}=7\mathrm{TeV}$. The LSTC limit curves for $\sin \chi =\frac{1}{4},\frac{1}{3},\frac{1}{2}$ assume that $M_{{\pi }_T}=0.75M_{{\rho }_T}-25\mathrm{GeV}$. Right: Two-dimensional exclusion plot for LSTC with $\sin \chi =1/3$ as described in the text. The CDF mass point is marked by the star (from Ref. 48).

Figure 12

The $M_{jj}$ and $M_{Zjj}$ distributions of ${\rho }_T^{\pm }$, $a_T^{\pm }\to WZ\to {\ell }^{+}{\ell }^{-}jj$ and backgrounds at the LHC for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. The cuts used are described in the text. The open red histograms are the ${\pi }_T$ and ${\rho }_T$ signals.

Figure 13

The $\Delta R$ and $\Delta \chi$ distributions of ${\rho }_T^{\pm }$, $a_T^{\pm }\to WZ\to {\ell }^{+}{\ell }^{-}jj$ and backgrounds at the LHC for $\sqrt{s}=8\mathrm{TeV}$ and $\int \mathcal{L}dt=20{\mathrm{fb}}^{-1}$. The cuts used are described in the text. The open red histograms are the signals.

Figure 14

The function $\ln (1+\Delta )$ defined in Eqs. (a5, a7). The Col du Delta at $\lambda =\pi /2$, $\Delta R=\pi$ is approached along the road $\lambda =\pi /2$. One cannot go over the pass and down the other side because the border is impassable. One must keep climbing along the ridge of increasing $\Delta R$ or return via the approach road.