我們研究一個簡單的現象學模型，它是在大強子對撞機（LHC）中，透過一個大質量向量傳遞子生成暗扇區。暗扇區粒子可能會衰變回標準模型粒子。它實現暗物質（DM）隱藏在大強子對撞機的多個量子色動力學噴流中（類量子色動力學噴流），即所謂的半可視噴流（SVJ）。在第一部分，我們比較MLM和CKKW-L兩個噴流匹配和合併的方案；CKKW-L方案有更好的表現，並在後續的研究中使用。第二部分研究了大強子對撞機中噴流和消失的橫能量之間的運動學以及在兩個暗扇區參數下的變化，即不可視率和暗禁閉尺度，對運動學行為的影響。

We study a simple phenomenological model which is the production of the dark sector via a heavy vector mediator at the Large Hadron Collider (LHC). The dark sector may decay back to Standard Model particles. It implements that dark matter (DM) conceals within multiple QCD jets (QCD-like) at the LHC, it is so-called semi-visible jets (SVJ). In the first part, two jet matching and merging schemes, MLM and CKKW-L, are compared; the CKKW-L scheme shows better performance and is used in the later study. The second part gives a study of the kinematics of jets and missing transverse energy at the LHC. We focus on variations of two dark sector parameters, invisible rate and dark confinement scale, to the behavior of kinematics.

[1] Maria Giulia Ratti. “Searching for Dark Matter in the Mono-Jet and Mono-Photon Channels with the ATLAS Detector”. PhD thesis. Milan U., 2018. doi: 10.13130/m-g-ratti_phd2018-02-12.
[2] Georges Aad et al. “Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s =8 TeV with the ATLAS detector”. In: Eur. Phys. J. C 75.7 (2015). [Erratum: Eur.Phys.J.C 75, 408 (2015)], p. 299. doi: 10.1140/ epjc/s10052-015-3517-3. arXiv: 1502.01518 [hep-ex].
[3] ATLAS Collaboration. “Sensitivity to WIMP Dark Matter in the Final States Containing Jets and Missing Transverse Momentum with the ATLAS Detector at 14 TeV LHC”. In: (2014). Tech. Rep. ATL-PHYSPUB-2014-007. url: https://cds.cern.ch/record/1708859.
[4] Daniel Abercrombie et al. “Dark Matter benchmark models for early LHC Run-2 Searches: Report of the ATLAS/CMS Dark Matter Forum”. In: Phys. Dark Univ. 27 (2020). Ed. by Antonio Boveia et al., p. 100371. doi: 10.1016/j.dark.2019.100371. arXiv: 1507.00966 [hep-ex].
[5] Timothy Cohen, Mariangela Lisanti, and Hou Keong Lou. “Semivisible Jets: Dark Matter Undercover at the LHC”. In: Phys. Rev. Lett. 115.17 (2015), p. 171804. doi: 10.1103/PhysRevLett.115.171804. arXiv: 1503.00009 [hep-ph].
[6] Timothy Cohen et al. “LHC Searches for Dark Sector Showers”. In: JHEP 11 (2017), p. 196. doi: 10 . 1007 / JHEP11(2017 ) 196. arXiv: 1707.05326 [hep-ph].
[7] Po-Jen Cheng. “Classification of Semi-visible Jets with Machine Learning”. MA thesis. National Tsing Hua University, 2020. url: https: //etd.lib.nctu.edu.tw/cgi-bin/gs32/hugsweb.cgi?o=dnthucdr& s=id=%22G021070225050%22.&searchmode=basic.
[8] Haim Goldberg and Lawrence J. Hall. “A New Candidate for Dark Matter”. In: Phys. Lett. B 174 (1986). Ed. by J. Tran Thanh Van, p. 151. doi: 10.1016/0370-2693(86)90731-8.
[9] Matthew J. Strassler and Kathryn M. Zurek. “Echoes of a hidden valley at hadron colliders”. In: Phys. Lett. B 651 (2007), pp. 374–379. doi: 10.1016/j.physletb.2007.06.055. arXiv: hep-ph/0604261.
[10] Maxim Pospelov, Adam Ritz, and Mikhail B. Voloshin. “Secluded WIMP Dark Matter”. In: Phys. Lett. B 662 (2008), pp. 53–61. doi: 10.1016/ j.physletb.2008.02.052. arXiv: 0711.4866 [hep-ph].
[11] Nima Arkani-Hamed et al. “A Theory of Dark Matter”. In: Phys. Rev. D 79 (2009), p. 015014. doi: 10.1103/PhysRevD.79.015014. arXiv: 0810.0713 [hep-ph].
[12] Aaron Pierce et al. “Searching for confining hidden valleys at LHCb, ATLAS, and CMS”. In: Phys. Rev. D 97.9 (2018), p. 095033. doi: 10.1103/PhysRevD.97.095033. arXiv: 1708.05389 [hep-ph].
[13] Hugues Beauchesne et al. “Collider phenomenology of Hidden Valley mediators of spin 0 or 1/2 with semivisible jets”. In: JHEP 08 (2018), p. 030. doi: 10.1007/JHEP08(2018)030. arXiv: 1712.07160 [hep-ph].
[14] Myeonghun Park and Mengchao Zhang. “Tagging a jet from a dark sector with Jet-substructures at colliders”. In: Phys. Rev. D 100.11 (2019), p. 115009. doi: 10.1103/PhysRevD.100.115009. arXiv: 1712.09279 [hep-ph].
[15] Graham D. Kribs et al. “Dark Mesons at the LHC”. In: JHEP 07 (2019), p. 133. doi: 10.1007/JHEP07(2019)133. arXiv: 1809.10184 [hep-ph].
[16] Elias Bernreuther et al. “Strongly interacting dark sectors in the early Universe and at the LHC through a simplified portal”. In: JHEP 01 (2020), p. 162. doi: 10.1007/JHEP01(2020)162. arXiv: 1907.04346 [hep-ph].
[17] Timothy Cohen, Joel Doss, and Marat Freytsis. “Jet Substructure from Dark Sector Showers”. In: JHEP 09 (2020), p. 118. doi: 10.1007/ JHEP09(2020)118. arXiv: 2004.00631 [hep-ph].
[18] Deepak Kar and Sukanya Sinha. “Exploring jet substructure in semivisible jets”. In: SciPost Phys. 10.4 (2021), p. 084. doi: 10.21468/ SciPostPhys.10.4.084. arXiv: 2007.11597 [hep-ph].
[19] Mihailo Backović et al. “Higher-order QCD predictions for dark matter production at the LHC in simplified models with s-channel mediators”. In: Eur. Phys. J. C 75.10 (2015), p. 482. doi: 10.1140/epjc/s10052- 015-3700-6. arXiv: 1508.05327 [hep-ph].
[20] Olivier Mattelaer and Eleni Vryonidou. “Dark matter production through loop-induced processes at the LHC: the s-channel mediator case”. In: Eur. Phys. J. C 75.9 (2015), p. 436. doi: 10.1140/epjc/s10052-015- 3665-5. arXiv: 1508.00564 [hep-ph].
[21] Matthias Neubert, Jian Wang, and Cen Zhang. “Higher-Order QCD Predictions for Dark Matter Production in Mono-Z Searches at the LHC”. In: JHEP 02 (2016), p. 082. doi: 10.1007/JHEP02(2016)082. arXiv: 1509.05785 [hep-ph].
[22] Morgan Svensson Seth. “A first study of Hidden Valley models at the LHC”. Bachelor thesis. Lund Observ., 2011. arXiv: 1106 . 2064 [hep-ph].
[23] J. Alwall et al. “The automated computation of tree-level and nextto-leading order differential cross sections, and their matching to parton shower simulations”. In: JHEP 07 (2014), p. 079. doi: 10.1007/ JHEP07(2014)079. arXiv: 1405.0301 [hep-ph].
[24] Adam Alloul et al. “FeynRules 2.0 - A complete toolbox for tree-level phenomenology”. In: Comput. Phys. Commun. 185 (2014), pp. 2250– 2300. doi: 10.1016/j.cpc.2014.04.012. arXiv: 1310.1921 [hep-ph].
[25] Torbjorn Sjostrand, Stephen Mrenna, and Peter Z. Skands. “A Brief Introduction to PYTHIA 8.1”. In: Comput. Phys. Commun. 178 (2008), pp. 852–867. doi: 10.1016/j.cpc.2008.01.036. arXiv: 0710.3820 [hep-ph].
[26] Torbjörn Sjöstrand et al. “An introduction to PYTHIA 8.2”. In: Comput. Phys. Commun. 191 (2015), pp. 159–177. doi: 10.1016/j.cpc. 2015.01.024. arXiv: 1410.3012 [hep-ph].
[27] Lisa Carloni, Johan Rathsman, and Torbjorn Sjostrand. “Discerning Secluded Sector gauge structures”. In: JHEP 04 (2011), p. 091. doi: 10.1007/JHEP04(2011)091. arXiv: 1102.3795 [hep-ph].
[28] Lisa Carloni and Torbjorn Sjostrand. “Visible Effects of Invisible Hidden Valley Radiation”. In: JHEP 09 (2010), p. 105. doi: 10.1007/ JHEP09(2010)105. arXiv: 1006.2911 [hep-ph].
[29] J. de Favereau et al. “DELPHES 3, A modular framework for fast simulation of a generic collider experiment”. In: JHEP 02 (2014), p. 057. doi: 10.1007/JHEP02(2014)057. arXiv: 1307.6346 [hep-ex].
[30] Richard D. Ball et al. “Parton distributions with LHC data”. In: Nucl. Phys. B 867 (2013), pp. 244–289. doi: 10.1016/j.nuclphysb.2012. 10.003. arXiv: 1207.1303 [hep-ph].
[31] Leif Lonnblad and Stefan Prestel. “Matching Tree-Level Matrix Elements with Interleaved Showers”. In: JHEP 03 (2012), p. 019. doi: 10.1007/JHEP03(2012)019. arXiv: 1109.4829 [hep-ph].
[32] Matteo Cacciari, Gavin P. Salam, and Gregory Soyez. “The anti-kt jet clustering algorithm”. In: JHEP 04 (2008), p. 063. doi: 10.1088/1126- 6708/2008/04/063. arXiv: 0802.1189 [hep-ph].
[33] Benjamin Nachman et al. “Jets from Jets: Re-clustering as a tool for large radius jet reconstruction and grooming at the LHC”. In: JHEP 02 (2015), p. 075. doi: 10.1007/JHEP02(2015)075. arXiv: 1407.2922 [hep-ph].
[34] Matteo Cacciari, Gavin P. Salam, and Gregory Soyez. “FastJet User Manual”. In: Eur. Phys. J. C 72 (2012), p. 1896. doi: 10.1140/epjc/ s10052-012-1896-2. arXiv: 1111.6097 [hep-ph].
[35] Matteo Cacciari and Gavin P. Salam. “Dispelling the N3 myth for the kt jet-finder”. In: Phys. Lett. B 641 (2006), pp. 57–61. doi: 10.1016/ j.physletb.2006.08.037. arXiv: hep-ph/0512210.
[36] Johan Alwall et al. “Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions”. In: Eur. Phys. J. C 53 (2008), pp. 473–500. doi: 10.1140/epjc/ s10052-007-0490-5. arXiv: 0706.2569 [hep-ph].
[37] Nils Lavesson and Leif Lonnblad. “Merging parton showers and matrix elements: Back to basics”. In: JHEP 04 (2008), p. 085. doi: 10.1088/ 1126-6708/2008/04/085. arXiv: 0712.2966 [hep-ph].
[38] Jessie Shelton. “Jet Substructure”. In: Theoretical Advanced Study Institute in Elementary Particle Physics: Searching for New Physics at Small and Large Scales. 2013, pp. 303–340. doi: 10.1142/9789814525220_ 0007. arXiv: 1302.0260 [hep-ph].
[39] Morad Aaboud et al. “Search for new phenomena in dijet events using 37 fb−1 of pp collision data collected at √ s =13 TeV with the ATLAS detector”. In: Phys. Rev. D 96.5 (2017), p. 052004. doi: 10.1103/ PhysRevD.96.052004. arXiv: 1703.09127 [hep-ex].
[40] Robert M. Harris and Konstantinos Kousouris. “Searches for Dijet Resonances at Hadron Colliders”. In: Int. J. Mod. Phys. A 26 (2011), pp. 5005–5055. doi: 10.1142/S0217751X11054905. arXiv: 1110.5302 [hep-ex].
[41] Nele Boelaert and Torsten Akesson. “Dijet angular distributions at s**(1/2) =14-TeV”. In: Eur. Phys. J. C 66 (2010), pp. 343–357. doi: 10.1140/epjc/s10052-010-1268-8. arXiv: 0905.3961 [hep-ph].