CMS-EXO-15-010

CMS-EXO-15-010 ; CERN-EP/2016-204
Search for long-lived charged particles in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
27 September 2016
Phys. Rev. D 94 (2016) 112004
Abstract: Results are presented of a search for heavy stable charged particles produced in proton-proton collisions at $\sqrt{s} =$ 13 TeV using a data sample corresponding to an integrated luminosity of 2.5 fb$^{-1}$ collected in 2015 with the CMS detector at the CERN LHC. The search is conducted using signatures of anomalously high energy deposits in the silicon tracker and long time-of-flight measurements by the muon system. The data are consistent with the expected background, and upper limits are set on the cross sections for production of long-lived gluinos, top squarks, tau sleptons, and lepton-like long-lived fermions. These upper limits are equivalently expressed as lower limits on the masses of new states; the limits for gluinos, ranging up to 1610 GeV, are the most stringent to date. Limits on the cross sections for direct pair production of long-lived tau sleptons are also determined.
Links: e-print arXiv:1609.08382 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Distribution of the ${ {\mathrm {d}}E/ {\mathrm {d}}x}$ estimator, ${I_{\mathrm {h}}}$ (see Section 3.1), versus particle momentum for tracks in the 13 TeV data, and for simulation of HSCP for singly or multiply charged particles with masses of 400 and 1000 GeV. The vertical scale shows the density of entries for data only.
png pdf	Figure 2: Observed and predicted mass spectra for loose selection candidates in the tracker-only (left) and tracker+TOF (right) analyses. The expected distributions for representative signals are shown as histograms.
png pdf	Figure 2-a: Observed and predicted mass spectra for loose selection candidates in the tracker-only analysis. The expected distributions for representative signals are shown as histograms.
png pdf	Figure 2-b: Observed and predicted mass spectra for loose selection candidates in the tracker+TOF analysis. The expected distributions for representative signals are shown as histograms.
png pdf	Figure 3: Observed and predicted mass spectra for candidates passing the final selection in the tracker-only (left) and tracker+TOF (right) analyses. The expected distributions for representative signals are shown as histograms.
png pdf	Figure 3-a: Observed and predicted mass spectra for candidates passing the final selection in the tracker-only analysis. The expected distributions for representative signals are shown as histograms.
png pdf	Figure 3-b: Observed and predicted mass spectra for candidates passing the final selection in the tracker+TOF analysis. The expected distributions for representative signals are shown as histograms.
png pdf	Figure 4: Results of the HSCP search as the cross section upper limits at 95% CL for various signal models for the tracker-only analysis (left) and tracker+TOF analysis (right) at $\sqrt {s} =$ 13 TeV. In the legend, ``CS'' stands for charge-suppressed interaction model.
png pdf	Figure 4-a: Results of the HSCP search as the cross section upper limits at 95% CL for various signal models for the tracker-only analysis at $\sqrt {s} =$ 13 TeV. In the legend, ``CS'' stands for charge-suppressed interaction model.
png pdf	Figure 4-b: Results of the HSCP search as the cross section upper limits at 95% CL for various signal models for the tracker+TOF analysis at $\sqrt {s} =$ 13 TeV. In the legend, ``CS'' stands for charge-suppressed interaction model.

Tables
png pdf	Table 1: Selection criteria for the two analyses with the number of predicted and observed events. In the background prediction, the statistical and systematic uncertainties are added in quadrature.
png pdf	Table 2: Systematic uncertainties for the two HSCP searches. All values are relative uncertainties in the signal acceptance for the tracker-only and tracker+TOF analyses.
png pdf	Table 3: Summary of the search for long-lived gluinos: the $ {p_{\mathrm {T}}} $ (GeV), $ {I_{\mathrm {as}}} $, $ {1/\beta } $, and mass thresholds M (GeV) requirements, the predicted and observed yields passing these criteria, and the resulting expected (exp.) and observed (obs.) cross section limits. The signal efficiencies and theoretical (theo.) cross sections are also listed.
png pdf	Table 4: Summary of the search for long-lived top squarks: the $ {p_{\mathrm {T}}} $ (GeV), $ {I_{\mathrm {as}}} $, $ {1/\beta } $, and mass thresholds M (GeV) requirements, the predicted and observed yields passing these criteria, and the resulting expected (exp.) and observed (obs.) cross section limits. The signal efficiencies and theoretical (theo.) cross sections are also listed.
png pdf	Table 5: Summary of the search for long-lived tau sleptons: the $ {p_{\mathrm {T}}} $ (GeV), $ {I_{\mathrm {as}}} $, $ {1/\beta } $, and mass thresholds M (GeV) requirements, the predicted and observed yields passing these criteria, and the resulting expected (exp.) and observed (obs.) cross section limits. The signal efficiencies and theoretical (theo.) cross sections are also listed.
png pdf	Table 6: Summary of the search for long-lived particles from modified Drell-Yan models of various charge: the $ {p_{\mathrm {T}}} $ (GeV), $ {I_{\mathrm {as}}} $, $ {1/\beta } $, and mass thresholds M (GeV) requirements, the predicted and observed yields passing these criteria, and the resulting expected (exp.) and observed (obs.) cross section limits. The signal efficiencies and theoretical (theo.) cross sections are also listed.
png pdf	Table 7: Mass limits obtained at $\sqrt {s}=$ 13 TeV for various HSCP candidate models compared with earlier results for $\sqrt {s}= $ 7+8 TeV [26]. In the model name, ``CS'' stands for charged suppressed interaction model and ``DY'' for Drell-Yan. The limits for doubly charged particles are also compared to the earlier CMS results obtained with the `multiply charged' analysis, which was specifically designed to search for multiply charged particles.

Summary

A search for heavy stable charged particles produced in proton-proton collisions at $\sqrt{s}= $ 13 TeV using the CMS detector is presented. Two complementary analyses were performed: using only the tracker and using both the tracker and the muon system. The data are found to be compatible with the expected background. Mass limits for long-lived gluinos, top squarks, tau sleptons, and multiply charged particles are calculated. The models for $R$-hadron-like HSCPs include a varying fraction of $ \tilde{\gamma} $-gluon hadronization and two different interaction models leading to a variety of exotic experimental signatures. The limits are significantly improved over those from Run 1 of the LHC, and the limits on long-lived gluinos, ranging up to 1610 GeV, are the most stringent to date.

References
1	M. Drees and X. Tata	Signals for heavy exotics at hadron colliders and supercolliders	PLB 252 (1990) 695
2	M. Fairbairn et al.	Stable massive particles at colliders	PR 438 (2007) 1	hep-ph/0611040
3	C. W. Bauer et al.	Supermodels for early LHC	PLB 690 (2010) 280	0909.5213
4	A. Kusenko and M. E. Shaposhnikov	Supersymmetric Q-balls as dark matter	PLB 418 (1998) 46	hep-ph/9709492
5	B. Koch, M. Bleicher, and H. Stoecker	Black holes at LHC?	JPG 34 (2007) S535	hep-ph/0702187
6	J. S. Schwinger	Magnetic charge and quantum field theory	PR144 (1966) 1087
7	D. Fargion, M. Khlopov, and C. A. Stephan	Cold dark matter by heavy double charged leptons?	Class. Quant. Grav. 23 (2006) 7305	astro-ph/0511789
8	A. C. Kraan	Interactions of heavy stable hadronizing particles	EPJC 37 (2004) 91	hep-ex/0404001
9	Particle Data Group Collaboration	Review of Particle Physics	CPC 38 (2014) 090001
10	ALEPH Collaboration	Search for pair production of long-lived heavy charged particles in $ e^+ e^- $ annihilation	PLB 405 (1997) 379	hep-ex/9706013
11	DELPHI Collaboration	Search for heavy stable and long-lived particles in $ e^+ e^- $ collisions at $ \sqrt{s} = $ 189 GeV	PLB 478 (2000) 65	hep-ex/0103038
12	L3 Collaboration	Search for heavy neutral and charged leptons in $ e^{+} e^{-} $ annihilation at LEP	PLB 517 (2001) 75	hep-ex/0107015
13	OPAL Collaboration	Search for stable and long-lived massive charged particles in $ e^+ e^- $ collisions at $ \sqrt{s} = $ 130 GeV to 209 GeV	PLB 572 (2003) 8	hep-ex/0305031
14	H1 Collaboration	Measurement of anti-deuteron photoproduction and a search for heavy stable charged particles at HERA	EPJC 36 (2004) 413	hep-ex/0403056
15	CDF Collaboration	Search for long-lived massive charged particles in 1.96~$ TeV \bar{p}p $ collisions	PRL 103 (2009) 021802	0902.1266
16	D0 Collaboration	Search for long-lived charged massive particles with the D0 detector	PRL 102 (2009) 161802	0809.4472
17	D0 Collaboration	Search for charged massive long-lived particles	PRL 108 (2012) 121802	1110.3302
18	D0 Collaboration	Search for charged massive long-lived particles at $ \sqrt{s}= $ 1.96 ~TeV	PRD 87 (2013) 052011	1211.2466
19	ATLAS Collaboration	Search for heavy long-lived charged particles with the ATLAS detector in pp collisions at $ \sqrt{s} = $ 7 TeV	PLB 703 (2011) 428	1106.4495
20	ATLAS Collaboration	Search for stable hadronising squarks and gluinos with the ATLAS experiment at the LHC	PLB 701 (2011) 1	1103.1984
21	ATLAS Collaboration	Search for massive long-lived highly ionising particles with the ATLAS detector at the LHC	PLB 698 (2011) 353	1102.0459
22	ATLAS Collaboration	Searches for heavy long-lived sleptons and R-Hadrons with the ATLAS detector in $ pp $ collisions at $ \sqrt{s}= $ 7 ~TeV	PLB 720 (2013) 277	1211.1597
23	ATLAS Collaboration	Search for long-lived, multi-charged particles in pp collisions at $ \sqrt{s}= $ 7 ~TeV using the ATLAS detector	PLB 722 (2013) 305	1301.5272
24	CMS Collaboration	Search for heavy stable charged particles in pp collisions at $ \sqrt{s}= $ 7 ~TeV	JHEP 03 (2011) 024	CMS-EXO-10-011 1101.1645
25	CMS Collaboration	Search for fractionally charged particles in $ pp $ collisions at $ \sqrt{s}= $ 7 TeV	PRD 87 (2013) 092008	CMS-EXO-11-074 1210.2311
26	CMS Collaboration	Search for heavy long-lived charged particles in pp collisions at $ \sqrt{s}= $ 7 TeV	PLB 713 (2012) 408	CMS-EXO-11-022 1205.0272
27	CMS Collaboration	Searches for long-lived charged particles in pp collisions at $ \sqrt{s}= $ 7 and 8~TeV	JHEP 07 (2013) 122	CMS-EXO-12-026 1305.0491
28	C. F. Berger, J. S. Gainer, J. L. Hewett, and T. G. Rizzo	Supersymmetry without prejudice	JHEP 02 (2009) 023	0812.0980
29	M. W. Cahill-Rowley, J. L. Hewett, A. Ismail, and T. G. Rizzo	More energy, more searches, but the phenomenological MSSM lives on	PRD 88 (2013) 035002	1211.1981
30	ATLAS Collaboration	Search for metastable heavy charged particles with large ionization energy loss in pp collisions at $ \sqrt{s} = $ 13 ~TeV using the ATLAS experiment	PRD 93 (2016) 112015	1604.04520
31	ATLAS Collaboration	Search for heavy long-lived charged $ {R} $-hadrons with the ATLAS detector in 3.2 fb$ ^{-1} $ of proton--proton collision data at $ \sqrt{s} = $ 13 ~TeV	PLB 760 (2016) 647	1606.05129
32	G. F. Giudice and A. Romanino	Split supersymmetry	NPB 699 (2004) 65	hep-ph/0406088
33	N. Arkani-Hamed, S. Dimopoulos, G. F. Giudice, and A. Romanino	Aspects of split supersymmetry	NPB 709 (2005) 3	hep-ph/0409232
34	J. L. Hewett, B. Lillie, M. Masip, and T. G. Rizzo	Signatures of long-lived gluinos in split supersymmetry	JHEP 09 (2004) 070	hep-ph/0408248
35	W. Kilian, T. Plehn, P. Richardson, and E. Schmidt	Split supersymmetry at colliders	EPJC 39 (2005) 229	hep-ph/0408088
36	N. Arkani-Hamed and S. Dimopoulos	Supersymmetric unification without low energy supersymmetry and signatures for fine-tuning at the LHC	JHEP 06 (2005) 073	hep-th/0405159
37	T. Sjostrand, S. Mrenna, and P. Z. Skands	A brief introduction to PYTHIA 8.1	CPC 178 (2008) 852	0710.3820
38	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC 76 (2016) 155	CMS-GEN-14-001 1512.00815
39	R. Mackeprang and A. Rizzi	Interactions of coloured heavy stable particles in matter	EPJC 50 (2007) 353	hep-ph/0612161
40	R. Mackeprang and D. Milstead	An updated description of heavy-hadron interactions in GEANT4	EPJC 66 (2010) 493	0908.1868
41	G. F. Giudice and R. Rattazzi	Theories with gauge mediated supersymmetry breaking	PR 322 (1999) 419	hep-ph/9801271
42	B. C. Allanach et al.	The Snowmass points and slopes: Benchmarks for SUSY searches	EPJC 25 (2002) 113	hep-ph/0202233
43	F. E. Paige, S. D. Protopopescu, H. Baer, and X. Tata	ISAJET 7.69: A Monte Carlo event generator for $ pp $, $ \bar{p} p $, and $ e^+e^- $ reactions		hep-ph/0312045
44	CMS Collaboration	Study of the underlying event at forward rapidity in pp collisions at $ \sqrt{s} = $ 0.9, 2.76, and 7~TeV	JHEP 04 (2013) 072	CMS-FWD-11-003 1302.2394
45	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
46	CMS Collaboration	Description and performance of track and primary-vertex reconstruction with the CMS tracker	JINST 9 (2014) P10009	CMS-TRK-11-001 1405.6569
47	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
48	CMS Collaboration	Jet performance in pp collisions at $ \sqrt{s}= $ 7 ~TeV	CMS-PAS-JME-10-003
49	CMS Collaboration	Particle--flow event reconstruction in CMS and performance for jets, taus, and $ E_{\mathrm{T}}^{\text{miss}} $	CDS
50	CMS Collaboration	Commissioning of the Particle-flow Event Reconstruction with the first LHC collisions recorded in the CMS detector	CMS-PAS-PFT-10-001
51	CMS Collaboration	CMS luminosity measurement for the 2015 data taking period	CMS-PAS-LUM-15-001	CMS-PAS-LUM-15-001
52	CMS Collaboration	Measurement of tracking efficiency	CMS-PAS-TRK-10-002
53	T. Junk	Confidence level computation for combining searches with small statistics	NIMA 434 (1999) 435	hep-ex/9902006
54	A. L. Read	Presentation of search results: the $ CL_s $ technique	JPG 28 (2002) 2693
55	T. L. H. C. G. The ATLAS Collaboration, The CMS Collaboration	Procedure for the LHC Higgs boson search combination in Summer 2011	CMS-NOTE-2011-005
56	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
57	W. T. Eadie et al.	Statistical methods in experimental physics	North Holland, Amsterdam
58	F. James	Statistical methods in experimental physics	World Scientific, Singapore
59	A. Kulesza and L. Motyka	Threshold resummation for squark-antisquark and gluino-pair production at the LHC	PRL 102 (2009) 111802	0807.2405
60	A. Kulesza and L. Motyka	Soft gluon resummation for the production of gluino-gluino and squark-antisquark pairs at the LHC	PRD 80 (2009) 095004	0905.4749
61	W. Beenakker et al.	Soft-gluon resummation for squark and gluino hadroproduction	JHEP 12 (2009) 041	0909.4418
62	W. Beenakker et al.	Supersymmetric top and bottom squark production at hadron colliders	JHEP 08 (2010) 098	1006.4771
63	W. Beenakker, R. Hopker, and M. Spira	PROSPINO: A program for the PROduction of Supersymmetric Particles In Next-to-leading Order QCD		hep-ph/9611232
64	P. M. Nadolsky et al.	Implications of CTEQ global analysis for collider observables	PRD 78 (2008) 013004	0802.0007