Discussion with LHCC Referees November 18, 2008

1. Discussion with LHCC RefereesNovember 18, 2008 • Memo sent to LHCC by LHCf • Answers to Michelangelo’s questions • Open point left from the previous meetings with referees • Winter activities

2. LHCf Memo: Main points • Our plan for the 2008/2009 winter shutdown is to continue working, focusing the activities mainly on the DAQ software and analysis programs. We do not plan to remove the detectors from the TAN during this shutdown, but we will adapt them to the Remote Handling System. • As is clearly stated in the LHCf TDR, our experiment has been designed to take data at 14 TeV center of mass energy, at low luminosity (<1031 cm-2 s-1). • If it happens that the luminosity will exceed this limit during 5+5 TeV operation in 2009, then LHCf will have to be removed from the TAN to avoid excessive radiation damage. • We are extremely interested in the 7+7 TeV running since only then can we completely fulfill our physics task, which was approved by LHCC. • If the LHCf has been removed during 2009 operation because the luminosity has exceeded 1031 cm-2 s-1, we strongly hope to have the possibility to re-install LHCf in the TAN region during the 2009/2010 winter shutdown, and then complete our physics program early in 2010 (in the commissioning phase of the 7+7 TeV running). • We therefore kindly ask to the LHCC to investigate this possibility, and we strongly hope that the committee will reconfirm our original request, described in the TDR, for a LHCf data taking period at 7+7 TeV.

3. Answers to Michelangelo’s questions • Is there a chance that with the current detectors you can take data already in 2009, regardless of the energy, and still preserve their functionaility for a final run at the highest energy in 2010? Could this be achieved by simply allowing for their removal after some integrated luminosity? I would find it really odd that you give up data taking in 09 simply because the energy is not at the highest value and you want to wait until that is available. • We completely agree with your opinions. It is very necessary to take data in 2009, and will try again the data taking at the highest energy in 2010.

4. Is there a value in taking data at 10 TeV? 10 TeV instead of 14 should reduce only by a factor of 2 the equivalent CR energy at which you will be probing the production properties (E_CR ~ E^2/mp). Is a factor of 2 gain in energy so critical in the tuning of the MCs that you are willing to postpone by 1 year the possible analysis of data? • Yes, there is a strong value in taking data at 10 TeV. It is our unexpected good chance to get data at different energies. It will bring us not only important results on the energy dependence, but on the reliability of the results. Moreover, from the scientific point of view, we may expect CGC (Color Glass Condensation), a new hint to supress very low-x gluons recently discussed for HERA data among hadron theorists, that may link to composition measurement in UHECRs. • They are discussing that it would be more important at LHC energy. We think they may appear also in LHCf as increasing energy, maybe near 14TeV. This is also a good motivation for taking data also at 10TeV as a reference (and also 450 GeV!).

5. 4 Composition fromAuger Xmax favors heavy primary Anisotropy favors light primary (if we trust in the AGN correlation) E>5.7.1019 eV

6. If indeed taking data in 2009 caused the detectors to fry and not be usable any longer in 2010 at the highest energy, is it conceivable to rebuild them? • We are planning to remove the detector during the high luminosity run. If it will not be possible, we are preparing to replace the plastic scintillators and the scintillating fiber belts, which might be damaged by a radiation dose greater than 10K rad.

7. Open points left from the previous meetings with referees Main point: What happens to the spectra if we trigger on the Double Arm Coincidence (for background rejection)? We certainly expect that the g and p0 spectra will change. We are studying by simulation how the spectra will be affected. We hope to have some results in the first months of 2009

8. Winter activities • Timing measurements for silicon  Done • Baking out of the paint in the TAN will not be done • We will not remove the detectors from the TAN • Remote Handling System (RHS) will be installed • We will modify the LHCf handling system to comply with the RHS • We are producing safety boxes to be installed above LHCf to avoid damages to the detectors • We will install the protection boxes before the end of 2008 • Improvements of the DAQ and analysis software • Improvement of the online analyzer • Improvement of the full data analysis flow (from DAQ to storage) • Alignment studies • Improve cluster finding on silicon part • Cross check of MC (EPICS based) simulation with Fluka code

9. Most important slides from the last LHCC presentation

10. Installation • Final installation was completed in January 2008 • No major problems have been found • Quartz fiber for laser calibration has been re-installed • Both Arm1 and Arm2 are working fine • No additional noise is found in the detectors, despite 200 m long power lines and signal cables (for the scintillators)

11. Front Counter • 2 fixed Front Counters were installed in front of Arm1 and Arm2 • They will not move with Arm1 and Arm2 • They are segmented in 2 x and 2 y slices • Very useful to check the beam quality and hence decide to move Arm1 and Arm2 in the operating position from the ‘garage’ position

12. After the installation…. • After the installation was completed, a lot of work on: • DAQ • New VME board to increase DAQ rate up to > 1 KHz • Integration of all the subsystem (Using MIDAS frame) • Analyzer to check the data quality and online monitor • Slow control software to control and monitor: • Power supplies • Manipulator • Temperature monitor • LHC interface • New NIM style board (CIBU) to send ‘PERMIT’ to LHC (KILL the beam in case of high rate) • Handhshaking software signals (DIP standard) for Injection, Adjust and Beam Dump • LHCf Physics information (beam position, rate, background etc.)

13. Synchronization with Atlas • To have the possibility to identify the events common with Atlas we implemented a synchronization method based on the L1A signal generated by Atlas. • We receive Atlas L1A and we store the time stamp of this signal in our DAQ system. • We can really correlate the Atlas events with the LHCf ones! Atlas Bunch ID – LHCf Bunch Id

14. p0 mass reconstruction  250 p0 events triggered (in a quite big background) and on disk Preliminary!!!! (MeV) • Main problems: • low photon energy (≥20 GeV) • Direct protons in the towers • Multi hits in the same tower Dm ~ 8 MeV Dm/m ~ 6%

15. ARM1 Position resolution 200 GeV electrons sx=172mm Number of event σx[mm] x-pos[mm] E[GeV] σy[mm] sy=159 mm Number of event y-pos[mm] E[GeV]

16. ARM2 Position Resolution 200 GeV electrons sx=40 mm x-pos[mm] sy=64 mm y-pos[mm] Alignment has been taken into account

17. Preparation for data taking The LHCf control room has been prepared and fully equipped in the Atlas area Furnitures Telephones Air conditioner Network Computers Printers ……

18. Dummy event

19. Important for machine tuning! Communications with LHC LHCf sends signals to LHC through the DIP system. Link have been tested and it works fine! • Experimental status (On/Off, Gain, etc.) • Detector position (Garage/Operating, position in mm, etc.) • Luminosity rate (Single and Double Arm) • Front Counter rate (single Arm, double Arm coincidence) • Small tower rate (single Arm) • Big tower rate (single Arm) • Double Arm coincidence rate (FC.AND.Towers in opposite sides) • Horizontal and Vertical position of the Beam (every 10000 events or in the whole RUN) • Injection Inhibit • Handshaking signals (Injection, Adjust, Beam Dump)

20. We are ready for data taking • On September 10 we observed some signals on Front Counters, with Arm1 and Arm2 in garage position for safety reasons • That day the Atlas BPTX signal was still not available (no info on the real bunches in the Atlas zone) • On September 11 Atlas gave us the synchronized BPTX signals, and we could take Front Counter data by using this signal (still in garage position) • We are measuring Beam-Gas from the Beam2 on Arm1 side

21. Front Counter signals