CMS-PAS-SUS-15-003

CMS-PAS-SUS-15-003
Search for new physics in the all-hadronic final state with the $M_{\mathrm{T2}}$ variable
CMS Collaboration
December 2015

Abstract: A search for new physics is performed using events with jets and the $M_{\mathrm{T2}}$ variable, which is a measure of the transverse momentum imbalance in an event. Results are based on a sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV with the CMS detector and corresponding to an integrated luminosity of 2.2 fb $^{-1}$ . No excess above the standard model background is observed. The results are interpreted as limits on the masses of potential new colored particles in a variety of simplified models of supersymmetry.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 10 (2016) 006.

Figures	References	CMS Publications

Figures
png pdf	Figure 1-a: Shape comparison between simulation and data for the $M_{\mathrm{T2}}$ observable. The left and right panels correspond to W+jets and $\mathrm{ t \overline {t} }$ +jets enriched control samples, respectively.
png pdf	Figure 1-b: Shape comparison between simulation and data for the $M_{\mathrm{T2}}$ observable. The left and right panels correspond to W+jets and $\mathrm{ t \overline {t} }$ +jets enriched control samples, respectively.
png pdf	Figure 2-a: The (a) plot shows the photon purity measured in data for the single photon control sample compared with the values extracted from simulation. The (b) plot shows $R(Z/\gamma )$ the $Z/\gamma$ ratio in simulation and data as a function of ${H_{\mathrm {T}}}$ , and the corresponding double ratio (bottom panel).
png pdf	Figure 2-b: The (a) plot shows the photon purity measured in data for the single photon control sample compared with the values extracted from simulation. The (b) plot shows $R(Z/\gamma )$ the $Z/\gamma$ ratio in simulation and data as a function of ${H_{\mathrm {T}}}$ , and the corresponding double ratio (bottom panel).
png pdf	Figure 3-a: The shape of the $M_{\mathrm{T2}}$ distribution from $\mathrm{Z} \rightarrow \nu \overline {\nu }$ simulation compared to shapes extracted from $\gamma$ and $W$ data control samples in the medium ${H_{\mathrm {T}}}$ and high ${H_{\mathrm {T}}}$ regions.
png pdf	Figure 3-b: The shape of the $M_{\mathrm{T2}}$ distribution from $\mathrm{Z} \rightarrow \nu \overline {\nu }$ simulation compared to shapes extracted from $\gamma$ and $W$ data control samples in the medium ${H_{\mathrm {T}}}$ and high ${H_{\mathrm {T}}}$ regions.
png pdf	Figure 4: Distribution of the ratio $r_{\phi }$ as a function of $M_{\mathrm{T2}}$ for the high $H_{\mathrm{T}}$ region. The fit is performed to the hollow, background-subtracted data points. The full points represent the data before subtracting non-QCD backgrounds using simulation. Data point uncertainties are statistical only. The red line and the band around it show the fit to a power-law function perfomed in the window 70 $< M_{\mathrm{T2}} <$ 100 GeV and the associated fit uncertainty.
png pdf	Figure 5-a: Values of $f_j$ (a) and $r_b$ (b) measured in data after requiring ${\Delta \phi _{\mathrm {min}}} <$ 0.3 radians and 100 $< M_{\mathrm{T2}} <$ 200 GeV. The bands represent both statistical and systematic uncertainties.
png pdf	Figure 5-b: Values of $f_j$ (a) and $r_b$ (b) measured in data after requiring ${\Delta \phi _{\mathrm {min}}} <$ 0.3 radians and 100 $< M_{\mathrm{T2}} <$ 200 GeV. The bands represent both statistical and systematic uncertainties.
png pdf	Figure 6: Comparison of the data-driven predictions of the multi-jet background in the toppological regions ( $M_{\mathrm{T2}} >$ 200 GeV) from the R\&S method and the ${\Delta \phi _{\mathrm {min}}}$ -ratio method. The uncertainties are statistical and systematic. Within each of the four $H_{\mathrm{T}}$ categories, all the estimates from the ${\Delta \phi _{\mathrm {min}}}$ -ratio method are correlated because they are derived from the same fit to the ${\Delta \phi _{\mathrm {min}}}$ -ratio data.
png pdf	Figure 7-a: (a) Comparison of estimated background and observed data events in each topological region. Hatched bands represent the full uncertainty on the background estimate. (b) Same for individual $M_{\mathrm{T2}}$ signal bins in the medium $H_{\mathrm{T}}$ region. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 7-b: (a) Comparison of estimated background and observed data events in each topological region. Hatched bands represent the full uncertainty on the background estimate. (b) Same for individual $M_{\mathrm{T2}}$ signal bins in the medium $H_{\mathrm{T}}$ region. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 8-a: Diagrams for the three scenarios of gluino mediated bottom squark, top squark and light flavor squark production considered.
png pdf	Figure 8-b: Diagrams for the three scenarios of gluino mediated bottom squark, top squark and light flavor squark production considered.
png pdf	Figure 8-c: Diagrams for the three scenarios of gluino mediated bottom squark, top squark and light flavor squark production considered.
png pdf	Figure 9: Exclusion limit at 95% CL for gluino mediated bottom-squark production. The area to the left of and below the thick black curve represents the observed exclusion region, while the dashed red lines indicate the expected limit and $\pm$ 1 standard-deviation. The thin black lines show the effect of the theoretical cross section uncertainties.
png pdf	Figure 10: Exclusion limit at 95% CL for gluino mediated top-squark production. The area to the left of and below the thick black curve represents the observed exclusion region, while the dashed red lines indicate the expected limit and $\pm$ 1 standard-deviation. The thin black lines show the effect of the theoretical cross section uncertainties.
png pdf	Figure 11: Exclusion limit at 95% CL for gluino mediated squark production, where the squark can be any of the first two generations. The area to the left of and below the thick black curve represents the observed exclusion region, while the dashed red lines indicate the expected limit and $\pm$ 1 standard-deviation. The thin black lines show the effect of the theoretical cross section uncertainties.
png pdf	Figure 12-a: (a) Comparison of the estimated background and observed data events in each signal bin in the mono-jet region. On the $x$ -axis, the $H_{\mathrm{T}}$ binning is shown (in GeV). Hatched bands represent the full uncertainty on the background estimate. (Below) Same for the very low $H_{\mathrm{T}}$ region. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 12-b: (a) Comparison of the estimated background and observed data events in each signal bin in the mono-jet region. On the $x$ -axis, the $H_{\mathrm{T}}$ binning is shown (in GeV). Hatched bands represent the full uncertainty on the background estimate. (Below) Same for the very low $H_{\mathrm{T}}$ region. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 13-a: (a) Comparison of the estimated background and observed data events in each signal bin in the low $H_{\mathrm{T}}$ region. Hatched bands represent the full uncertainty on the background estimate. Same for the high (middle) and extreme (b) $H_{\mathrm{T}}$ regions. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 13-b: (a) Comparison of the estimated background and observed data events in each signal bin in the low $H_{\mathrm{T}}$ region. Hatched bands represent the full uncertainty on the background estimate. Same for the high (middle) and extreme (b) $H_{\mathrm{T}}$ regions. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 13-c: (a) Comparison of the estimated background and observed data events in each signal bin in the low $H_{\mathrm{T}}$ region. Hatched bands represent the full uncertainty on the background estimate. Same for the high (middle) and extreme (b) $H_{\mathrm{T}}$ regions. On the $x$ -axis, the $M_{\mathrm{T2}}$ binning is shown (in GeV). Bins with no entry for data have an observed count of 0.
png pdf	Figure 14: Comparison of post-fit background prediction and observed data events in each topological region. Hatched bands represent the post-fit uncertainty on the background prediction. For the monojet, on the $x$ -axis the $H_{\mathrm{T}}$ binning is shown (in GeV).
png pdf	Figure 15: Post-fit background prediction, expected signal yields and observed data events in each topological region. Hatched bands represent the post-fit uncertainty on the background prediction. For the monojet, on the $x$ -axis the $H_{\mathrm{T}}$ binning is shown (in GeV). The compressed-spectra signal model considered here is gluino-mediated bottom-squark production with mass of the gluino and LSP equal to 700 and 600 GeV, respectively.
png pdf	Figure 16: Post-fit background prediction, expected signal yields and observed data events in each signal bin in the extreme $H_{\mathrm{T}}$ region. Hatched bands represent the post-fit uncertainty on the background prediction. On the $x$ -axis the $M_{\mathrm{T2}}$ binning is shown (in GeV). The open-spectra signal model considered here is gluino-mediated bottom-squark production with mass of the gluino and LSP equal to 1500 and 100 GeV, respectively.

References
1	ATLAS Collaboration	Summary of the searches for squarks and gluinos using $\sqrt{s}=8$ TeV pp collisions with the ATLAS experiment at the LHC	JHEP 10 (2015) 054	1507.05525
2	ATLAS Collaboration	ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider	EPJC75 (2015), no. 10, 510	1506.08616
3	CMS Collaboration	Searches for Supersymmetry using the M $_{T2}$ Variable in Hadronic Events Produced in pp Collisions at 8 TeV	JHEP 05 (2015) 078	CMS-SUS-13-019 1502.04358
4	CMS Collaboration	Search for Supersymmetry Using Razor Variables in Events with $b$ -Tagged Jets in $pp$ Collisions at $\sqrt{s} =$ 8 TeV	PRD91 (2015) 052018	CMS-SUS-13-004 1502.00300
5	CMS Collaboration	Search for new physics in the multijet and missing transverse momentum final state in proton-proton collisions at $\sqrt{s}$ = 8 TeV	JHEP 06 (2014) 055	CMS-SUS-13-012 1402.4770
6	CMS Collaboration	Search for gluino mediated bottom- and top-squark production in multijet final states in pp collisions at 8 TeV	PLB725 (2013) 243--270	CMS-SUS-12-024 1305.2390
7	CMS Collaboration	Search for supersymmetry in hadronic final states with missing transverse energy using the variables $\alpha_T$ and b-quark multiplicity in pp collisions at $\sqrt s=8$ TeV	EPJC73 (2013), no. 9	CMS-SUS-12-028 1303.2985
8	CMS Collaboration	Search for supersymmetry in hadronic final states using $M_\mathrm{T2}$ in pp collisions at $\sqrt{s} = 7$ TeV	JHEP 10 (2012) 018	CMS-SUS-12-002 1207.1798
9	C. G. Lester and D. J. Summers	Measuring masses of semiinvisibly decaying particles pair produced at hadron colliders	PLB 463 (1999) 99	hep-ph/9906349
10	CMS Collaboration	Particle-Flow Event Reconstruction in CMS and Performance for Jets, Taus, and MET	Technical Report CMS-PAS-PFT-09-001, CERN
11	CMS Collaboration	Commissioning of the Particle-flow Event Reconstruction with the first LHC collisions recorded in the CMS detector	CDS
12	M. Cacciari, G. P. Salam, and G. Soyez	The anti- $k_t$ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
13	CMS Collaboration	Determination of jet energy calibration and transverse momentum resolution in CMS	JINST 6 (2011) P11002	CMS-JME-10-011 1107.4277
14	CMS Collaboration	Performance of b-Tagging Algorithms in 50ns Data at 13 TeV	CDS
15	CMS Collaboration	Electron reconstruction and identification at sqrt(s) = 7 TeV	CDS
16	CMS Collaboration	Performance of CMS muon reconstruction in $pp$ collision events at $\sqrt{s}=7$ TeV	JINST 7 (2012) P10002	CMS-MUO-10-004 1206.4071
17	CMS Collaboration	Jet Performance in pp Collisions at 7 TeV	CDS
18	T. Sj\"ostrand	The Lund Monte Carlo for e $^{+}$ e $^{-}$ Jet Physics	CPC 28 (1983) 229
19	T. Sj\"ostrand, S. Mrenna, and P. Skands	PYTHIA 6.4 physics and manual	JHEP 05 (2006) 026	hep-ph/0603175
20	CMS Collaboration	Missing transverse energy performance of the CMS detector	JINST 6 (2011) P09001	CMS-JME-10-009 1106.5048
21	J. Alwall et al.	MadGraph 5: going beyond	JHEP 06 (2011) 128	1106.0522
22	T. Sjostrand, S. Mrenna, and P. Z. Skands	A Brief Introduction to PYTHIA 8.1	CPC 178 (2008) 852--867	0710.3820
23	GEANT4 Collaboration	GEANT4---a simulation toolkit	NIMA 506 (2003) 250
24	S. Abdullin et al.	The fast simulation of the CMS detector at LHC	J. Phys. Conf. Ser. 331 (2011) 032049
25	CMS Collaboration	Search for New Physics with Jets and Missing Transverse Momentum in $pp$ collisions at $\sqrt{s}=7$ TeV	JHEP 08 (2011) 155	CMS-SUS-10-005 1106.4503
26	A. L. Read	Presentation of search results: The $CL_{s}$ technique	JPG 28 (2002) 2693
27	A. L. Read	Modified frequentist analysis of search results (The $CL_{s}$ method)	CERN-OPEN 205(2000)
28	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
29	ATLAS and CMS Collaborations	Procedure for the LHC Higgs boson search combination in summer 2011	CMS-NOTE-2011-005
30	CMS Collaboration	Search for top-squark pair production in the single-lepton final state in pp collisions at $\sqrt{s}$ = 8 TeV	EPJC73 (2013), no. 12	CMS-SUS-13-011 1308.1586