ACORDE and Cosmic Rays Physics at LHC S ACORDE and Cosmic Rays Physics at LHC S. Kartal University of Istanbul -Turkey C.E. Pagliarone Univeristy of Cassino & INFN Pisa On the behalf of the ACORDE Collaboration

Outline Motivations ACORDE (the ALICE COsmic Rays Detector) Physics Goals Other Cosmic Ray Activities at Cern Recent Results from ACORDE New Proposal for CR at ALICE to fill

Motivations (I) Our primary goal is to study muons attaching to extensive air showers initiated by primary CRs interacting in the upper atmosphere, is to study high multiplicity muon bundles which might signify: High energy physics effects in the primary interaction that are not included in current Monte Carlo programs simulating UHECR: Coherent effects in nucleus-nucleus interactions Coherent pion production Primarily at energies above 1016 eV Study of Muon Bundels : Search for Large muon multiplicities (~100 ) in multi-muon events: The transverse size of muon bundels is sensitive to the mass of the primary nucleus including the shower. Psossible exotic Physics suggested by the theoretical specilations: Collisions of Strange Quark Matter (SQM) with air nuclei Formation of Quark Gluon Plasma (QGP) in Iron-Air collisions

Motivations (II) It seems highly desirable to employ a multi-100 million $ detector and its infrastructure for multiple purposes Hence, to use one of the large LHC detectors to help elucidate some of the UHECR puzzles is a “highly beneficial” activity, involving a relatively small additional effort We are proposing to use ALICE

Tracking cosmic muons in ALICE The main advantages of such possibility are: - The flux of cosmic  at the ALICE location is shielded by 30 m rock, with an energy threshold of 15 GeV or less (much lower than for large underground experiments, hence a much higher rate). - The rock composition over ALICE is well known. The surface near the ALICE location is flat within at least 100 m radius, so its effect on  absorption and energy loss may be evaluated. - The ALICE tracking detectors may be tuned to reconstruct the energy and charge state of muons with good resolution up to several hundred GeV.

High Energy Cosmic Rays Cosmic ray showers: Dynamics of the high energy particle spectrum is crucial

Motivations (III) A secondary goal of our muon studies is to better understand the mass composition and energy spectrum of primary CR nuclei; Observing, simultaneously, the muonic content and the EM component, via surface arrays, provides a handle on the composition primarily for 1-100 PeV

IP4

ACORDE Size: 16 x 26 meters Weight: 10,000 tons TPC TRD TOF

The ACORDE Detector This modules were used by DELPHI experiment before. We reproduce most of parts and using at ACORDE now!

The ACORDE Detector 20x373 cm Plastic Scintillators 60 Double Layer Modules 60 double layer modules. Each module have an active area of 186x19 cmx2 and Photo Multipler.

Top Modules

Bottom Modules

CR physics with ALICE Two main aspects: Better knowledge - through the study of pp, pA and AA collision events - of the hadronic interactions at high energy ----> interest in the interaction of CR with atmosphere Measurements of cosmic rays with ALICE itself and (possibly) additional detectors ---> properties of the m spectrum at ground Additional use of cosmics in ALICE for calibration and alignment; ACORDE + TPC + TRD + TOF Sofisticated tracking system, precise measurement of particle momentum and muon energy up to 1-2 TeV (B = 0.5 T); Capability to track high density of muons

Physics topics of interest Multi-muon events  most promising CosmoAleph measurements Inclusive muons (single muon) L3+C measurements Cosmic ray point sources, Antiproton flux limit Large area coincident experiment

CHALLENGE: L3+C measurements “Measurement of the shadowing of high energy cosmic rays by the Moon: A search for TeV-energy antiprotons”, Astroparticle Phys. 23(2005)p411. “Observation of a Flare Signal from a fixed position in the hemisphere through muons with L3+C”, ICRC 2005. “A search for low velocity exotic particles with the L3+C spectrometer”, ICRC 2005. “Search for Kolar-like Measurement of the atmospheric muon spectrum from 20 to 3000GeV”, Phys. Lett. B (2004)p15. “The L3+C detector, a unic tool-set to study cosmic rays”,NIMA 488(2002)p209.

Simulation programs to explain the data CORSIKA code  Hadronic interaction models : QGSJET, VENUS, DPMJET, NEXUS, SIBYLL … The models are tuned using data from accelerators p-p, p-pbar A-A collisions. Usually at Tevatron energies ~ 1015 eV or s1/2 = 630 or 900 GeV LHC energy s1/2 = 14 TeV  proton with E = 1017 eV with fixed target Much above the energy of the knee of cosmic rays (E=3·1015 eV) The most relevant measurements for ALICE are : the pseudo-rapidity distributions of identified hadrons the hadron transverse momentum distributions Considerable interesting should be the study of N-N interactions Center of mass energy 630 or 900 GeV

The muon spectrum at sea level Transport Equations describe the propagation of particles through the Atmosphere, resulting in a m-flux (zenith angle and energy dependent) and muon charge ratio at sea level. Muon momentum spectrum; Muon charge ratio;

Multiplicity distribution of charged particles with different hadronic interaction models Heck, Nucl. Phys B, 2003

The muon P(m) spectrum First plot is experimental results and second plots from theoretical prediction In spite of great experimental efforts, measurements of the muon flux and energy distribution at the ground level show relative discrepancies up to 15-20 % in the region 10-1000 GeV/c Vertical differential muon spectrum predicted by a number of models. Also predictions differ by up to 30 %.

Muon charge ratio Rm First graph is generated from Theortical models and second graph from experimental results Determined mainly by the behaviour of the inclusive cross section in the fragmentation region. It contains information on the charge and mass composition of the primary flux. Vertical muon charge ratio predicted by several models: differences by 10-20 % in the region 10-1000 GeV/c.

The trigger conditions Running during standard ALICE data taking imposes stringent conditions for cosmic trigger: low trigger rate (few Hz) live time constrictions (statistical problems) Inclusive muons trigger  450 Hz (too high) We can take only vertical muons  60-70 Hz (high) Statistical problems to measure : Single muon momentum distribution and charge ratio Point source in a standard way Antiproton flux limit Multi-muon events  few Hz

Multi-muon events 76 tracks in the TPC t = 174 days of data taking COAMOALEPH: Astroparticle Physics 19 (2003) 513-523 Multim. events Emth= 70 GeV Standard LEP trigger : cosmic muons deposit energy in the e.m. and hadronic calorimeter Selection: events without reconstructed vertex at least one track p>5 GeV/c 76 tracks in the TPC 580000 events during 1997-99 runs t = 174 days of data taking t = 20 days effective run time

Multi-muon events ALEPH ALICE Fe 1012<E<1017 eV p 1012<E<1017 eV

Reminder of Results from ALEPH Conclusions (1) on frequency: The bulk of the data could be successfully described by standard production phenomena The muon multiplicity distribution favors a composition that changes from light to heavier elements with increasing energy around the “knee” at 1015-15.5 eV The five highest multiplicity events occur with a frequency which is almost an order of magnitude above the simulation

Reminder of Results from ALEPH Conclusions (2) on properties: High multiplicity muon bundles are almost parallel, with the muons distributed uniformly over the ALEPH area 4x3 m2 The interaction characteristics of forward particle production at energies beyond the current accelerator range (Eprim > 3x1015 eV) cannot be explored Even in the accelerator range, forward particle production that is relevant for CR studies is poorly understood Similar results found by DELPHI and L3

Muon energy measurements Some contribution to disentangle among primaries could come from the measurement of the energy of each muon. This is a really new measurement never done in cosmic ray underground apparatus Average energy of muons in the core for different number m in the core of the shower. Proton and Fe primary E = 1015 eV

Muon Angular (q) distribution Angular distribution of muons impacting the ground upon the ALICE cavern; Angular distribution of muons reaching the ALICE magnet.

Muon DP distribution DP=PSurface(m)-PMagnet(m) 1M atmospheric m generated at the surface, pointing to the ALICE’s IP DP=PSurface(m)-PMagnet(m)

1° TPC CR Event triggered by ACORDE

CRALP Proposal for Cosmic Rays with ALICE and P2 Plans for Cosmic Ray studies at CERN combining Surface Array at P2 with ACORDE Underground Array at UX2 and ALICE TPC detector at UX2

Concept: 30 m of rock E > 20 GeV

ALICE TPC/TRD The TPC diameter is 5 m and it is 5.1 m long Outside the TPC at 2.9 < r < 3.7 m is a TRD 7 m long

The next step We have two existing surface arrays now taking data at P2 and P4: At P4: there are 3 rows of 7, 6 and 7 1m2 counters in an area 10 x 60 m2 (since Fall 2001)

At P4

The next step At P2: there are 40 0.5m2 counters in 6 rows covering an area 50 x 70 m2 (since 2000) The two sets of arrays have been running consistently since April 2005 The goal here is to look for coincidences over a range of about 8 km

At P2

Plans for counter design Working on: Design of the Sc/fiber/box Base design HV setup Readout TDC/ADC

Prototype

PULSE HEIGHT from prototype: With 16 fibers MIP = 27 FWHM = 31 HV = 2000 V Allow for up to 20 mips 27 ch.

Proposal: To put about 100 additional counters above ground at P2, 5-10 (?) counters above ALICE, with Another 100 counters underground around ALICE Trigger: on counters above and around ALICE; readout ALICE and all P2 counters Schedule: Discussions with ALICE are underway and there was already interest from ALICE (TDR)

BACK UP SLIDES

Studies from QGSJET CORSIKA MC No. of muons Fe protons Separation (E > 70 GeV) No. EM showers

Integral flux of high energy cosmic rays Measurements of the very forward energy flux (including diffraction) and of the total cross section are essential for the understanding of cosmic ray events At LHC pp energy: 104 cosmic events km-2 year-1 sr-1 > 107 events at the LHC in one day TeV LHC

High Energy Cosmic Rays Interpreting cosmic ray data depends on hadronic simulation programs The forward region is poorly known/constrained Models differ by factor 2 or more Need forward particle/energy measurements: e.g. dE/d…

The next step: V. Avati et al: “a larger underground array (typically 400 m2) with precise muon chambers complemented by a surface array …. to study further with much larger statistics the properties of the outstanding highest multiplicity events.” We propose to use the ALICE TPC and TRD (~50 m2), with a smaller overburden (E > 20 GeV) and a much longer data taking time Combined with the existing CR shower array above ALICE at P2 to measure EM content, and Combined with additional counters underground both above and around the ALICE detector