October 29, 2018 The FP420 R&D Project: Higgs and New Physics with forward protons at the LHC M. G. Albrow1, R. B. Appleby2, M. Arneodo3, G. Atoian4, I.L. Azhgirey5, R. Barlow2, I.S. Bayshev5, W. Beaumont6, L. Bonnet7, A. Brandt8, P. Bussey9, C. Buttar9, J. M. Butterworth10, 11 2, 12 13 7 14 M. Carter , B.E. Cox ∗, D. Dattola , C. Da Via , J. de Favereau , D. d’Enterria , 12 14,6, 6 8,† 14 7 P. De Remigis , A. De Roeck ∗, E.A. De Wolf , P. Duarte , J. R. Ellis , B. Florins , J. R. Forshaw13, J. Freestone13, K. Goulianos15, J. Gronberg16, M. Grothe17, J. F. Gunion18, J. Hasi13, S. Heinemeyer19, J. J. Hollar16, S. Houston9, V. Issakov4, R. M. Jones2, M. Kelly13, C. Kenney20, V.A. Khoze21, S. Kolya13, N. Konstantinidis10 , H. Kowalski22, H.E. Larsen23, V. Lemaitre7, S.-L. Liu24, A. Lyapine10, F.K. Loebinger13, R. Marshall13, A. D. Martin21, J. Monk10, I. Nasteva13, P. Nemegeer7, M. M. Obertino3, R. Orava25, V. O’Shea9, S. Ovyn7, A. Pal8, S. Parker20, J. Pater13, A.-L. Perrot26, T. Pierzchala7, A. D. Pilkington13, J. Pinfold24, K. Piotrzkowski7, W. Plano13, A. Poblaguev4, V. Popov27, K. M. Potter2, S. Rescia28, F. Roncarolo2, A. Rostovtsev27, X. Rouby7, M. Ruspa3, M.G. Ryskin21, A. Santoro29, N. Schul7, G. Sellers2, A. Solano23, S. Spivey8, W.J. Stirling21, D. Swoboda26, M. Tasevsky30, R. Thompson13, T. Tsang28, P. Van Mechelen6, A. Vilela Pereira23, S.J. Watts13, M. R. M. Warren10, G. Weiglein21, T. Wengler13, S.N. White28, B. Winter11, Y. Yao24, D. Zaborov27, A. Zampieri12, M. Zeller4, A. Zhokin6,27 FP420 R&D Collaboration 1Fermilab, 2University of Manchester and the Cockcroft Institute, 3Università del Piemonte Orientale, Novara, and INFN, Torino, 4Yale University, 5State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 6Universiteit Antwerpen, 7Université Catholique de Louvain, 8University of Texas at Arlington, 9University of Glasgow, 10University College London (UCL), 11Mullard Space Science Laboratory (UCL), 12INFN Torino, 13University of Manchester, 14CERN, PH Department, 15Rockefeller University, NY, 16Lawrence arXiv:0806.0302v2 [hep-ex] 2 Jan 2009 Livermore National Laboratory (LLNL), 17University of Wisconsin, Madison, 18UC Davis, 19IFCA (CSIC-UC, Santander), 20Molecular Biology Consortium, Stanford University, 21Institute for Particle Physics Phenomenology, Durham, 22DESY, 23Università di Torino and INFN, Torino, 24University of Alberta, 25Helsinki Institute of Physics, 26CERN, TS/LEA, 27ITEP Moscow, 28Brookhaven National Lab (BNL), 29Universidade do Estado do Rio De Janeiro (UERJ), 30Institute of Physics, Prague ∗Contact persons: [email protected], [email protected] †Now at Rice University Abstract We present the FP420 R&D project, which has been studying the key aspects of the development and installation of a silicon tracker and fast- timing detectors in the LHC tunnel at 420 m from the interaction points of the ATLAS and CMS experiments. These detectors would measure precisely very forward protons in conjunction with the corresponding central detectors as a means to study Standard Model (SM) physics, and to search for and characterise New Physics signals. This report includes a detailed description of the physics case for the detector and, in particular, for the measurement of Central Exclusive Production, pp p+φ+ p, in which the outgoing protons remain intact and the central→ system φ may be a single particle such as a SM or MSSM Higgs boson. Other physics topics discussed are γγ and γp interactions, and diffractive processes. The report includes a detailed study of the trigger strategy, acceptance, recon- struction efficiencies, and expected yields for a particular p p pH p measurement with Higgs boson decay in the bb¯ mode. The document→ also describes the detector acceptance as given by the LHC beam optics between the interaction points and the FP420 location, the machine back- grounds, the new proposed connection cryostat and the moving (“Ham- burg”) beam-pipe at 420 m, and the radio-frequency impact of the design on the LHC. The last part of the document is devoted to a description of the 3D silicon sensors and associated tracking performances, the design of two fast-timing detectors capable of accurate vertex reconstruction for background rejection at high-luminosities, and the detector alignment and calibration strategy. 2 Contents 1 Introduction ...................................... 6 1.1 Executivesummary ................................ 6 1.2 Outline......................................... 7 1.3 Integration of 420 m detectors into ATLAS and CMS forward physics programs . 8 2 The Physics Case for Forward Proton Tagging at the LHC . .......... 9 2.1 Introduction .................................... 9 2.2 The theoretical predictions . ....... 11 2.3 Standard Model Higgs boson . 13 2.4 h,H intheMSSM................................... 14 2.5 Observation of Higgs bosons in the NMSSM . ....... 18 2.6 Invisible Higgs boson decay modes . ....... 20 2.7 Conclusion of the studies of the CEP of h,H ..................... 21 2.8 Photon-photon and photon-proton physics . .......... 22 2.9 Diffractivephysics .............................. 34 2.10 Physics potential of pT measurements in FP420 . 38 2.11 Otherphysicstopics............................. ..... 39 3 Simulated measurement of h bb¯ intheMSSM.................... 41 → 3.1 Trigger strategy for h bb¯ .............................. 43 → 3.2 Experimental cuts on the final state . ........ 44 3.3 Results and significances . ..... 46 3.4 Inclusion of forward detectors at 220 m . ........ 48 3.5 Comparison of the h,H bb¯ analyses ........................ 50 → 3.6 Recent improvements in background estimation . ........... 51 4 LHC Optics, acceptance, and resolution . ......... 53 4.1 Introduction .................................... 53 4.2 Detectoracceptance.............................. 54 4.3 Massresolution .................................. 58 4.4 Opticssummary................................... 61 5 Machine Induced Backgrounds . 62 5.1 Introduction .................................... 62 5.2 Near beam-gas background . 62 5.3 Beamhalo....................................... 63 3 5.4 Halo from distant beam-gas interactions . .......... 69 5.5 Secondary interactions . ..... 70 5.6 Machine background summary . 75 6 A new connection cryostat at 420 m . ..... 77 6.1 Cryostatsummary................................. 80 7 Hamburgbeam-pipe.................................. 82 7.1 Introduction .................................... 82 7.2 FP420movingpipedesign ........................... 82 7.3 PocketDesignandTests............................ 83 7.4 Testbeamprototype............................... 87 7.5 Motorization and detector system positioning . ............ 87 7.6 System operation and safeguards . ....... 90 7.7 Hamburg pipe summary and outlook . ..... 91 8 RFimpactofHamburgpipeonLHC . 93 8.1 Motivation and introduction . ....... 93 8.2 Longitudinal impedance . ..... 94 8.3 Transverse impedance and beam instability . ........... 98 8.4 Coupling with detectors . ..... 99 8.5 RFsummary...................................... 99 9 Silicon Tracking Detectors . 100 9.1 Introduction .................................... 100 9.2 3D silicon detector development . .......101 9.3 Tracking detector mechanical support system . ...........109 9.4 High-voltage and low-voltage power supplies . ...........121 9.5 Readout and infrastructure at the host experiment . .............132 9.6 ThermalDesign................................... 134 9.7 Performance of the tracking system . ........140 10 FastTimingDetectors .............................. 146 10.1 Overlap background and kinematic constraints . .............146 10.2 Timing......................................... 146 10.3 Timingdetectors................................ 148 10.4 Detector simulations . 150 10.5 Performance in test-beam measurements . ..........152 4 10.6 Electronics and data acquisition . ..........154 10.7 Referencetimesystem ............................ 155 10.8 Central detector timing . 157 10.9 Timing summary and future plans . 158 11 Alignment and calibration . 161 11.1 Alignment requirements . 161 11.2 Beam and proton transfer calculations . ..........164 11.3 Machinealignment ............................... 165 11.4 Mass scale and resolution measurement with physics processes . 165 11.5 Alignmentsummary............................... 169 12 Near detector infrastructure and detector services . ................171 13 Conclusions ...................................... 174 14 Costing.......................................... 177 5 1 Introduction 1.1 Executive summary Although forward proton detectors have been used to study Standard Model (SM) physics for a couple of decades, the benefits of using proton detectors to search for New Physics at the LHC have only been fully appreciated within the last few years [1, 2, 3, 4, 5, 6]. By detecting both outgoing protons that have lost less than 2% of their longitudinal momentum [7], in conjunction with a measurement of the associated centrally produced system using the current ATLAS and/or CMS detectors, a rich programme of studies in QCD, electroweak, Higgs and Beyond the Standard Model physics becomes accessible, with the potential to make unique measurements at the LHC. A prime process of interest is Central Exclusive Production (CEP), pp p + φ + p, in which the → outgoing protons remain intact and the central system φ may be a single particle such as a Higgs boson. In order to detect both outgoing protons in the range of momentum