First collisions in LHC Jeroen van Tilburg (Universität Zürich) Highlights from startup run 2009. Many exciting achievements in few weeks time. Preliminary or very preliminary results. Comparisons between experiments very provisional. Most results already shown on Dec 18 (2nd LHC status report). Bias towards LHCb. The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

LHC timeline Timeline of the world’s most powerful particle accelerator Nov Dec 20 21 22 23 24 25 26 27 28 29 30 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 Nov 20 Both beams complete a few turns. Nov 23 First proton-proton collisions at injection energy of 450 GeV. Nov 29 World-record beam energy of 1.18 TeV established. Dec 5 First multi-bunch beams in the LHC (2 bunches per beam) Dec 6 First collisions with stable beams 4x4 pilots at 450 GeV, rate ~ 1 Hz → first time silicon detectors fully operational. Dec 8 Accelerated both beams to 1.18 TeV with 2 bunches for the first time. Dec 11 Collisions with stable beams 4x4, >1010 per bunch, at 450 GeV, rate ~10 Hz. Dec 12-13 High intensity runs (~50 Hz) with ~1 million collisions at 450 GeV and 50k collisions at 1.18 TeV. Dec 16 End of 1st successful period of operation. 27 days of very successful beam commissioning. → Restart on February 15, 2010 for a short technical stop: Commissioning for higher energies (3.5 TeV beam) Upgrade of CMS cooling system → Follow the LHC live on twitter.com/lhc The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

LHC beam commissioning LHC is back! Very careful planning, adjusted on daily basis. Many systems working from day 1. Around the clock availability of accelerator and detector components. Provided detectors with many useful collisions at 450 GeV and 1.18 TeV. LHC Page 1: Ramp to 1.18 TeV The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

Event displays from 23rd Nov First collisions! The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg And then... The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg Calibration → LHCb TT detector: time alignmnent < 2 ns Time alignment First alignment silicon detectors on 6 Dec (1 Hz) Stable beam declared early morning. Redone on 11 Dec with higher statistics (10 Hz) Use bunch id’s to distinguish collisions from beam gas and cosmics. Spatial alignment Already in good shape thanks to data from cosmics and injection tests. Still in progress → mass resolutions will improve with time. Understanding of magnetic field Example from LHCb Cosmic runs and injection tests done with field off. First data with magnetic field. → got polarity wrong initially  Calibration has started. First mass peaks at right place  Other calibrations → drift time, calorimeters, material map, jet energy scale, PID, etc. The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

Beam position Beam accurately monitored by experiments Example → LHCb VELO detector VELO halves can be moved in and out. During injection VELO at 30 mm from beam. Nominal position sensors at 8 mm from beam. At 450 GeV VELO can not yet be fully closed (beam too wide). → each side at 15 mm from nominal (i.e. 17 mm from beam). Important to closely monitor the beam before closing! xz distribution of beam-gas vertices Measure dimensions of luminous regions: beam 1 beam 2 The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg Data distribution Over a million particle collisions distributed smoothly for analysis around the world on the LHC computing grid Two copies of raw data → one at CERN, one at a Tier 1 DST available soon after data acquisition finished. → Example: LHCb < 1 hour. → Includes reconstruction. Example from LHCb: reprocessed complete dataset in less than 2 hours (done twice already) Total @ 900 GeV Full det @ 900 GeV Total @ 2.36 TeV ALICE > 1 M 30k ATLAS 920k 540k 34k CMS 400k 20k (full CMS) LHCb Fraction with collisions ~ 30-60% The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

Charged particle multiplicity 900 GeV In progress 2.36 TeV ALICE submitted to EPJC 28 Nov 2009 First physics output ALICE already submitted paper on charged particle multiplicity at 900 GeV. dN/dh = 3.10 ± 0.13 (stat) ± 0.22 (syst) Work in progress for 2.36 TeV. CMS has measured dN/dh between -2 < h < 2 CMS The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg The particle zoo The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg Ks0 → π+ π− ATLAS ALICE PDG = 497.6 MeV CMS M = 497.7 ± 0.1 MeV/c2 s = 7.6 ± 0.1 MeV/c2 M = 497.3 ± 0.2 MeV/c2 s = 4.3 ± 0.1 MeV/c2 (w/o Velo) s =9.5 MeV/c2 LHCb The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg Λ0 → p+ π− ATLAS ALICE PDG = 1115.7 MeV CMS M = 1115.9 ± 0.1 MeV/c2 s = 3.1 ± 0.1 MeV/c2 M = 1115.6 ± 0.1 MeV/c2 s = 1.4 ± 0.1 MeV/c2 (w/o Velo) s =3.1 MeV/c2 LHCb The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

First collisions in LHC, Jeroen van Tilburg φ(1020) → K+ K− ALICE PDG = 1019.5 MeV LHCb M = 1019 ± 1 MeV/c2 s = 3.9 ± 0.8 MeV/c2 CMS The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

Rest of the zoo Found cascade decays Looking already for J/ψ’s X ® Lp ® pp p ALICE Looking already for J/ψ’s LHCb LHCb CMS Dimuon candidate: M = 3.03 GeV Dimuon candidate: M = 3.035 GeV The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

Conclusions Looking forward for LHC restart on February 15th! LHC and experiments have performed extremely well and swift Beam commissioning well underway. Successful collection of the first LHC collision data. Smooth data transfer worldwide via Grid. Extremely rapid production of first (albeit very preliminary) results. Now experiments have time to digest the data. Further calibration (alignment) and analysis. Looking forward for LHC restart on February 15th! The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg

pp-collision and beam-gas animation The New, the Rare and the Beautiful, 06.01.2010 First collisions in LHC, Jeroen van Tilburg